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Antenna Systems Information
(antennas, feedlines, duplexers, circulators, isolators, calculators, etc.)
Compiled from a multitude of sources and donations by
Mike Morris WA6ILQ
(callsign) at repeater-builder dot com
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Note that the contents of this page, like most here at www.repeater-
builder.com, are totally dependent on donations of information.
If you have something to share please consider writing it up and sending it in.
If you have relevant data sheets, class handouts or any other
information that we do not have here, please consider scanning
them and emailing us the scans.
If you don't have access to a scanner we can arrange to get
documents scanned and made into a PDF for download.
Please email Mike WA6ILQ at (callsign) //at// repeater-builder //dot// com for details.
Just in case you are trying to locate some documentation...
Phelps-Dodge (also known as PD) was bought by Celwave (year?), which was bought by Radio
Frequency Systems (aka RFS) (year?) whose web site is at http://www.rfsworld.com/RFSGlobal. If
you are looking for other web pages containing information on a specific
antenna - for example some repeater group whose web page mentions a Phelps-Dodge
PD-458 in passing - you may have to check under all three company names.
For example, under Google, you would type (less the square brackets): [ "Phelps
Dodge" OR Celwave OR "Radio Frequency Systems" OR "RFS" 458 ].
Note that the OR parameter in a Google search must be in ALL CAPS.
Antenna Specialists was sold to PCTel (year?) - and their corporate web
site is at http://www.antenna.com, and
the product web site is at http://www.antenna.com/products.html. The 2-way mobile product model number lookup page is at http://www.antenna.com/lm_cat/index.html.
I was told recently that PCTel bought both Maxrad and Antennex (but I don't know the dates)
DB Products was bought by Andrew, but they didn't want everything. The leftovers
(including duplexers) are now sold by a company called dbSpectra, located in Lewisville, Texas (the web site is at http://www.dbspectra.com). From their web site: "...in December of 2004, dbSpectra signed a licensing agreement with Andrew Corporation to manufacture and sell the Legacy Decibel Products site management equipment such as filters, duplexers, combiners, tower top amplifiers and more. These products had been outsourced and dbSpectra successfully brought them back and have since hired many of the personnel involved in the design and manufacture of these excellent products."
In March of 2006 the Laird Group of England (AKA LairdTech) purchased Antenex for about $20.5 million, and then in Febuary of 2007 bought Cushcraft for about $90 million.
And about month later Andrew purchased the English manufacturer Precision Antennas for about $36 million.
In December of 2007 Andrew was bought by CommScope for US$2.6 Billion.
In many cases you will find that manufacturers web sites have theoretical information
that is applicable to all... i.e. the theory articles on Manufacturer "X" products applies
to Manufacturer "Y" and to "Z". Sometimes researching other manufacturers web sites can
save you a lot of money... for example, if Manufacturer "X" claims that a crystal filter
will solve your desense problem. Then you go to "Y"s web site and there you discover that,
yes, a crystal filter can be used in the receiver feedline to notch out a local signal, or
to pass your signal. What the Manufacturer "X" web site didn't tell you, and the Manufacturer "Y " or "Z" web site did, is that in your specific case it may not work. Unless you were familiar with crystal filters you would not know that the insertion loss can be as high as 12db, which in many cases makes a crystal filter on a repeater receiver unusable.... the signal level budget just isn't there (i.e. while adding the crystal filter would kill the interfering signal, it also reduced your receiving range to 1/2 of what it was, or maybe even less). So do your homework
and learn all you can about the theory behind the hardware before you hand over your money.
System Engineering
A system's coverage area is primarily determined by how well it receives stations in the field, not by how much transmitter power it has. Both the receiver and the transmitter depend on antennas - and both it and the feedline are usually the most critical components in any amateur radio station, be it a home station, a mobile, a repeater, a remote base or a point-to-point link. Perversely they are usually are the most difficult to install, maintain, or troubleshoot - and usually during extreme climate conditions like in freezing temperatures and / or high winds. If you are installing a repeater that will be used in any type of emergency services situations it does not make any sense to go "cheap" on the antenna system. Creative (legal) aquisition of good quality equipment, yes. Low or poor quality equipment, no... that decision will always come back and haunt you. Simply put, a good antenna will hear and talk better than a poor antenna and for a lot longer. If you go with quality hardware and proper installation the first time you won't have to do it over (like my dad used to say about both hand and power tools: "buying quality only hurts once"). A good Phelps-Dodge, DB Products or Sinclair antenna connected to 7/8 inch Heliax feedline (you can use 1/2 inch on 6m or 10m) will last over 20 years of seriously hostile winters. How many Comets or Diamonds or replacement lengths of RG-series feedline will you buy and install in the same 20 years ?
A preamp can help some systems, but realize that preamps are all about the internal noise figure (NF) of the preamp and the amount of gain it provides. The lower the NF, the weaker the signal that will be heard. Regarding gain, most modern preamps have gain on the order of 14-18dB in a single stage. That's enough to take a signal that's barely above the noise floor and make it very usable on a decent receiver. But don't attempt to use a preamp to make up for a long, lossy feedline - once you've lost the signal all the preamp does is amplify what's left (the noisy signal). Likewise don't attempt to use a preamp to make up for a poor receiver - fix or replace the receiver. There are ways to put a preamp up at the antenna (but only if it is a receive-only antenna). Many sites use shared "community receive" antennas that feed a preamp/multicoupler panel - at one site I visit semi-regularly there is a single UHF (406-512 MHz) Sinclair antenna that feeds all of the UHF system receivers (over 35 of them).
On the transmit side, never forget that SWR is not the only measure of antenna performance. A low SWR only means that the transmitter is "seeing" a reasonably non-reactive load. That is, it looks like a 50 ohm resistor (a dummy load). The SWR tells you nothing about what is really important, the antenna efficiency, the antenna noise level, its pattern (gain) and decoupling of the RF from the feedline. And don't forget that the feedline loss runs both directions and can dramatically affect the SWR reading !! Your transmitter sends power up the feedline (let's say it's 100 watts), and some gets lost going up (let's say that it's 20% and 80w gets there). The lightning-damaged antenna reflects some power back down (let's say it's 10%, or 8 watts). The 8 watts comes back down, and 20% gets lost, and you see 6.4 watts on the Bird wattmeter. So you see 100 going up and 6.4 coming back, and you think the SWR is a lot better than it really is at the antenna. Look at this web page on the topic: Power Antenna Manufacturing Inc. SWR Calculator (an off-site link). It removes the "masking effect" of the feedline loss.
And before you sign a site agreement, pay your money, and go to the trouble of installing a system, measure the noise floor on your frequency at the site. Just borrow an appropriate already-installed antenna for fifteen minutes (with permission) and make the measurement (i.e. if you are installing a VHF system use a VHF antenna). If site A has a 0.8uv noise floor (due to the broadcast and paging systems there) and site B has a 0.1uv noise floor take a guess as to which site will hear better (and I have seen sites that have noise floors that are above 2.0 uv on the frequency of interest). You may chose to install a UHF system at a particular site if the noise floor on VHF is intolerable (or vice versa). And with repeaters it all depends on how well you hear (see the article on measuring effective sensitivity below). Given the limits of antenna power rating, feedline and local geography, increasing the talk range is easy - how much amplifier, duplexer and antenna can you afford?
In most repeaters the duplexer provides a certain amount of isolation between the receiver and the transmitter (some systems, like those that use two antennas, or even two sites, don't use duplexers). If the amount of isolation, however it is acquired, is greater than what is required (the excess is sometimes referred to as "headroom"), then the system design is adequate for the job (see the article Some thoughts on Repeater Receiver-to-Transmitter Isolation below). That situation is fine until they decide to add a preamp to help out the handheld users. Then they discover that the amount of isolation isn't enough. They forgot that you need (at least) the same amount of extra isolation ("headroom") as the amount of gain the preamp provides, since it raises the apparent noise floor as well as the signal of interest. In most cases you will have to fight with desense when you add a preamp (a top-quality preamp like an AngleLinear will help). Always have enough extra headroom in your duplexer to handle any of a couple of situations: First, the site owner adds additional repeaters to the site, or second, that you want to add a preamp later on. If the duplexer is your primary provider of receiver-to-transmitter isolation do not scrimp on the duplexer. Next to a good antenna and feedline the duplexer is the most critical part of a good repeater system. Long ago I gave up on four-cavity duplexers (two cavities on each side) on VHF/2m, 222 MHz and UHF, I use the six cavity pass/reject type exclusively. Duplexer tuning is very, very critical. A return loss bridge is nice, a spectrum analyzer with a tracking generator is the second choice. It is possible to tune one without a spectrum analyzer, but an analyzer is the best way and the only good way to tell if it is tuned correctly. And don't tune the duplexer on the ground, then transport it to the site over a bumpy four-wheel-drive road, and expect it to be as precisely tuned when you get there. Always have the test gear with you at the site to verify final tuning after mounting it in the system rack.
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Getting the most from your
repeater system By Kevin Custer W3KKC
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Recommended
Coax and Connectors for the iDEN Enhanced Base Transceiver System Motorola Engineering wrote this three page discussion of cable and connector types with regard to combining, intermodulation, and other RF performace factors. They concluded that LMR-nnn and LMR-nnnn series cable is specifically NOT recommended in any radio site RF environments, especially duplex environments. While iDEN is a 900 MHz system the physics are the same at 28 MHz through 1296 MHz. Well worth reading.
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HELIAX Coaxial Cable for Low Intermodulation Generation Andrew Engineering wrote this one page writeup on why foil-braid cable causes intermod. Despite the fact that you'd expect that conclusion from the makers of Heliax there's a lot less sales pitch and a lot more engineering presented than you'd think. Worth reading.
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Where exactly is your repeater? And
are you really sure? Read this before you file any paperwork and help out your local coordination folks, and prevent an FCC or FAA citation. Donated by Eric Lemmon WB6FLY |
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MIL-STD-188-124B "Grounding, Bonding, and
Shielding for Common Long Haul/Tactical Communication Systems including Ground Based Communications-Electronics Facilities and Equipments" 3.8mb
PDF file dated 01-Feb-92
This is the newer military handbook on grounding, and is a quicker read at about 40 pages, however it says on the second page of the forward that "This Standard is further implemented by MIL-HDBK-419", listed below. This handbook is approved for public release and distribution is unlimited. |
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MIL-HDBK-419A "Grounding, Bonding, and
Shielding for Electronic Equipments and Facilities" 9.6mb PDF file dated 29-DEC-1987
This is the big military handbook on grounding. It is large, in two volumes totaling about 812 pages. Volume one is 396 pages of theory, volume two is 394 pages of practice. This download is the complete 2 volume set in one PDF file, and volume 2 starts on page 419 of the file. This book covers grounding for safety, lightning, nuclear blast and most everything else. A very good read and a real eye opener. This handbook is approved for public release and distribution is unlimited.
At one point (Feb 1999), the hardcopy (including postage) was FREE if you ordered it from:
Commanding Officer
Naval Publication and Forms Center
5801 Taylor Avenue
Philladelphia PA 19120
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MIL-STD-464 "Department of Defense Interface Standard Electromagnetic Environmental Effects Requirements for Systems" 1.17mb PDF file dated 18-Mar-97
"This standard establishes electromagnetic environmental effects (E3) requirements and verification criteria for airborne, sea, space, and ground systems, including associated ordnance." This handbook is approved for public release and distribution is unlimited.
Why, you might ask, is this one on a web page that covers antenna systems? Well, "electromagnetic environmental effects" includes lightning. And lightning can have seriously negative effects on antenna systems (and the radios they are connected to).
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RF Communications - A Non
Technical Approach By Decibel Products Corp.
Many years ago Decibel Products (a major RF hardware manufacturer) published a series of informative pamphlets on systems engineering topics. The earliest seems to be 1964. The topics included Base Station Antennas, Combiners, Selective Cavities, Duplexers, RF Transmission Lines and Lightning. All five pamphlets were recently combined into a single PDF document titled "RF Communications - A Non-Technical Approach". DB made it available on their web site at http://www.decibelproducts.com/collateral/aboutrfcommunications.pdf.
This document should be required reading for anyone wanting to learn about
antenna systems. (thanks to Duane Hall KA8GVH for the pointer)
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TX-RX Tech Aid #77001 Some
very useful charts and procedures. Worth printing and adding to your tech notebook. By TX-RX Corp. |
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Help!! My repeater seems deaf By Kevin K. Custer W3KKC |
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Is a 3 DB change in power really worth it? The answer is "It Depends" By Neil Johnson WBØEMU If you are in charge of maintaining a repeater system, or building a new one, then this is worth reading. |
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Some thoughts on Repeater Receiver-to-Transmitter Isolation By Mike Morris WA6ILQ |
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Guidelines for mounting
antennas on towers A scan of a guidelines page
covering tower-to-antenna distances - donated by Skipp |
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ANTPLOT - A Side-Tower Mounted Antenna Pattern
Prediction Program This is a Zip file of both version 5.3 and of
version 5.4 of the DOS program originally provided by Antenna Specialists. It's
noted as being "Program No. 3 of the Antenna Specialists RF TOOLS Series". Also
called "tplot" for some reason. Donated by A. Nony Mous
Does anyone have Program #1, #2 and any others?
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High power amplifiers and duplex radio Tubes vs. Transistors, By Kevin Custer W3KKC Short version: at high power levels tubes win. |
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Is this connector any good? An
article on the perils of cheap connectors by Jeff DePolo WN3A
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EMR Corp. Technical Papers
Index An index of downloadable PDF papers on Isolators, Duplexer
retuning, Ferrite and Hybrid Combiners, Multicouplers, Preselectors, Bandpass
and Pass-Notch Cavity Resonators.
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Using Preamps with repeaters... and why
sometimes you wouldn't want to... by Mark Malm NØFAZ and Kevin K. Custer W3KKC |
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The Effects
of Trees on Slant Propagation Paths By Vogel & Hagn This is
an academic paper that will be of special interest to UHF, 900 & 1200 MHz
system owners. |
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Best Practices Guide
By Motorola Inc. This is a write up on solving interference problems
at 800 MHz and oriented towards Public Safety communications, but it's worth
reading by any repeater owner or builder.
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Interference
Technical Appendix By Motorola Inc. This is intended
to be an add-on to the "Best Practices Guide" above. Also
very worth reading.
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Calculating Your Radio Horizon By
A. Nony Mous |
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Radio Mobile Coverage
prediction software by Roger Coudé VE2DBE A bit of a learning
curve, but darn good stuff (offsite link)
A Yahoo group supporting it is at http://groups.yahoo.com/group/Radio_Mobile_Deluxe
If anybody wants to put together a "Getting Started" article,
we'll make room for it here. |
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The calcualtors, especially Dale Bickels HAAT, Coordinate and Distance calculators are useful. Scroll down to the Calculators section for them.
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Combiners
A Combiner is a system of cavities and optionally isolators (or cavities and optionally circulators paired with external loads) that allows multiple transmitters to share one transmitting antenna, but at a cost. Some combiner systems can cost you from 50% to 75% of your transmit power... i.e. that 100 watt repeater transmitter that gave you N miles radius coverage on a stand-alone antenna may only have the performace of a 50 watt or 25 watt system once the combiner is in line. Also don't forget that the antenna the combiner is feeding has a finite power limit. Some are rated at 200 watts, and by the time you combine 5 transmitters, each with 100 watts out, through a 3db loss combiner, that's still 250 watts that's going up the hose to the antenna, and (poof) goes the antenna (and the combiner needs a dummy load that can handle 250w continuous duty, and good ventillation). Note that systems that use combiners usually have a separate receiving antenna that is multicoupled to each receiver.
Additional detail for this introductary paragraph, and additional articles / publications on this topic are welcome. One useful article would be how to pick the frequencies that can be combined onto a single antenna.
About Combiners By DB Products, copyrighted 1975.
From the preface: "This booklet has been written for the many people engaged in two-way radio communications who are NOT radio engineers. A non-technical presentation of a rather complex subject has been attempted in an effort to bring about a better understanding of combiners used in two-way radio systems."
Tuning
Procedure for Two-Transmitter Combiners DB4351, DB4381, DB4352, DB4382,
DB4384
Two page
64kb PDF describing the tuneup of a unit that is essentially two
isolators, two low pass filters, a hybrid coupler and a dummy load.
Tuning Instructions for
the DB4350 and DB4360 Low Loss Combiners 8kb A one-page
PDF file.
Tuning
Instructions for the DB4379 Low Loss Combiner 9kb A
one-page PDF file describing a unit for up to 8 transmitters.
Isolators and Circulators
Comments below are compiled and summarized from several postings on the
repeater-builder yahoogroup.
A circulator is a magnetic ferrite three-port device that acts like a one-way-valve for RF energy, and the third port usually has a dummy load attached. A isolator is just a circulator with a built-in or bolted-on load (usually fairly low in power handling capability) so as long as you stay within the power handling limits of the load all comments below on isolators also apply to circulators and vice
versa. Isolators and circulators are physically fragile devices - and for this reason you
NEVER want to pay full price for any isolator or circulator that has a dent (or other damage) in
the housing that could have been created by dropping it. If you plan on using your own
dummy load on a new circulator, you should send that dummy load with the circulator to the vendor
so that the circulator can be properly tuned. Due to the variation in impedance and return
loss between individual dummy loads (even if outwardly identical), it is never a good idea to change
the load(s) after an isolator is properly tuned. Hint: put a stripe of nail polish across the
connectors of the isolator and the load, and use an obnoxious color (like fluorescent pink,
bright orange or purple). If anybody swaps the loads (or even borrows it and replaces it) then it will be obvious.
If you see a "4-port circulator" advertised it's probably a dual stage circulator with two devices
in one box with the output of the first fed into the input of the second, and two dummy load ports.
Triple circulators also exist, and in fact were a factory option on the Motorola MSF5000 stations.
One characteristic of isolators / circulators is that they generate
harmonics. This property is inherent to the device and cannot be "tuned
out". For this reason, an isolator is always followed by a bandpass
or low pass filter in any application where good engineering practice is
followed. This same situation is why folks say that isolators cause
intermod. They do, but when installed properly, the pass cavity kills off any
harmonics (which precludes the intermod from ever being created). NEVER, EVER
have an isolator looking directly into an antenna !
Example: Years ago I heard about a 52.525 MHz remote base (on a UHF repeater) that
had a circulator and no pass cavity on the 6m transmitter. At the same site
was a 420.200 MHz RX that was one end of a point-to-point link. So? you ask... Well, the 8th harmonic of 52.525 MHz is dead on
420.200 MHz. Whenever the remote base transmitted it trashed 105.05 MHz
in the FM band, 157.575 MHz, and since 5 KHz deviation at 52 MHz is
40 KHz at 420 MHz it trashed 420.175 MHz, 420.200 MHz and 420.025 MHz...
Ooops.
When you rent space at a 2-way site and are handed the contract terms do not be surprised to
see the requirement of an "intermod panel" on each transmitter. This "panel" consists of
either (a) an isolator followed by a pass cavity, or (b) a circulator, an external dummy load,
and a pass cavity. Many radio communications equipment manufacturers make isolators and circulators: Andrew, Connecticut Microwave, EMR, Celwave, Decibel Products, MECA, REC-USA, Raditek, Telewave,
TX-RX, and many more. Contact suppliers such as TESSCO or Talley for prices and
availability (and make sure you are sitting down when you ask the price). Contact
information is on the suppliers index page at this web
site, or you can use Google.
IMPORTANT: The frequency "range" shown on the spec sheet for an
isolator / circulator is not the field tuning range of the device, it
is in reality an indicator of the manufacturer's capability to build a device to any
one particular frequency. For example, once an isolator / circulator
is made for a particular high band frequency, it can only be tuned about two to three
percent either side of that frequency (figure 2 to 3 MHz at 2M / high
band) and retain optimum performance. Once outside of that "window" (which is
4 to 6 MHz wide at 2M / high band), it will cost between $200 and $300
(about 1/3 of the new price) to have an isolator / circulator remanufactured
from (for example) a 165 MHz frequency to your specific 146 MHz frequency (or
from a commercial UHF frequency to your 440 MHz frequency) because it involves a
considerable amount of precision bench work using RF test equipment, special mechanical
tools and professional skills that very few shops or people have: copper or bronze vises
(nonmagnetic) to position and clamp the isolator "just right" and nonmagnetic tools
to do the actual assembly or repair, plus a network analyzer to get the RF performance
"just right". Besides, having your unit rebuilt by a person who does it 8 hours
a day, and every day guarantees that it is done right the first time, it comes with a
factory guarantee and lands in your hand already precision tuned on your frequency with
a warranty and some nice proof-of-performance plots. And it is much cheaper
than buying a new device ! Be forewarned: Once you open an isolator or
circulator housing the manufacturer may refuse to perform the rework - it's way
too easy to crack a magnet or something and then all you have is an expensive
precision doorstop or paperweight... (and I've seen a damaged low band isolator being
used as a doorstop).
Remember that an isolator / circulator is a MAGNETIC device, and don't mount it
on a steel rack panel... you WILL detune it... use aluminum panels only, using brass
screws and aluminum standoffs if you need standoffs (or use a block of wood). I'm
only mentioning it because I forgot when I was cleaning up a cabinet - the UHF circulator
was floating in the breeze, supported by the 7/8 inch heliax jumpers, so I rearranged
things and mounted it to the same panel as the UHF pass cavity... then the system
transmitter performance dropped like a rock. A group member that lived in the
fringe area of the system (he had a 6-element beam on his tower fixed pointed at the
repeater) reported that the system went from its normal 90% quieting at his site to
1/3 quieting. It was only after I measured the SWR between the isolator and the
transmitter did I realize that the isolator was detuned... I switched the mounting back
to "in the breeze" and the system performance went back to normal... The
temporary mounting the following day was a piece of 1x6 inch pine shelving mounted to
the rack rails with drywall screws through the holes in the rail into the wood. The
permanent fix a couple of weeks later was relocating the pass cavity and the isolator to an
aluminum panel and using brass screws to mount the isolator to the panel. The pass
cavity didn't care, I used regular screws for that.
If you are going to make any adjustments to an isolator / circulator do it with
low power - 2 to 5 watts, maybe 10 watts max, and EACH port must be terminated with
a 50 ohm load. You don't want any off-resonance circulating currents or voltages
during tuneup... at high levels they could demagnetize (or change the permanent
fields of) the internal magnets and damage the isolator. Also when tuning, in an
ideal environment you would have available another (already tuned) isolator to
put between the transmitter and the isolator being tuned to make sure the unit under
adjustment sees a consistent 50 ohm source... in other words, the first one isolates
the transmitter from the one being adjusted...
If circulators and isolators are a new topic to you, I suggest that you read the
first three articles below, especially the one by William F. Lieske. Yes,
there is some repeated material between the articles, but if you're new to yhe
topic, it won't hurt. When you have multiple people writing on the same topic
some repetition is inevitable.
What's a circulator? a.k.a. Properties of
a Ferromagnetic Circulator By Kevin Custer W3KKC
The Care and Feeding of the R.F. Isolator
a 14kb PDF by William F. Lieske, Sr. Founder, EMR Corporation
An Elementary Introduction to Ferrite Isolators, Circulators and RF Loads a 1mb PDF file A TX-RX Corp. "Seminar Series" writeup - 14 pages.
Field
Tuning Instructions for Dual Junction Tunable Isolators a
one-page 21kb PDF file by Decibel Products
Generic single-section isolator tuning
instructions from EMR a 26kb PDF file donated by Eric Lemmon
WB6FLY
Generic dual-section isolator tuning
instructions from EMR a 55kb PDF file donated by Eric Lemmon
WB6FLY
Sinclair's instructions on tuning
isolators Donated by Eric Lemmon WB6FLY
Microwave
Associates 7R011 Isolator Tuning Instructions Donated by Micheal Salem N5MS
Good for
125 watts, with 0.9 db insertion loss typical with 1.3 db max. The isolation
can be as high as 60 db with 50 db typical.
Data
sheet on the DB 4318H-2C High Band Single Channel filter and isolator
A
two-page PDF file describing a Decibel Products 164 - 168.5 MHz dual isolator
but the directions apply to similar units. The drawing is in error, it does not
show the termaline on the output port.
Cavities, Duplexers, Theory, and More
The purpose of a duplexer is to allow the simultaneous operation of a receiver
and a transmitter on the same antenna... but saying "duplexer" is like saying
"car". They come in various types, makes, models, and performance levels. Some
are notch-only, others are notch-pass. There are 3-cavity, 4-cavity, 5-cavity,
and there are 6-cavity models (more cavities give a higher level of receiver-to-transmitter
isolation, but at a cost of insertion loss). In general, the higher the RF level
at a site (i.e. how many other systems there are, and the power levels involved), the more
cavities you need. If you run a split site system at a leow RF level site you
may not need a duplexer. And depending on circumstances even a single site
system can be built with no duplexer at all.
A duplexer is made up of a number of cavities and critical length cables, each of which
adds to the total transmit-to-recieve isolation provided by the assembly. If
you're just starting out, I suggest that you read the first eight articles below,
expecially those by Jacques Audet VE2AZX, John Portune W6NBC and by William F. Lieske. Yes,
there is some repeated material between the articles, but if you're new to
duplexers, it won't hurt. When you have multiple people writing on the same
topic some repetition is inevitable. The 8 articles collectively will give
you a basic education on duplexers.
Note that duplexers are initially tuned and the ports labeled at
the factory. A duplexer is built with a "higher" side and a "lower" side,
and the loops and inter-cavity cabling are selected for those frequencies. The
application a ham has may conflict with the original port labels. Most
commercial repeaters (definitely in UHF, usually on VHF) receive on the higher
frequency and transmit on the lower frequency, whereas amateur repeaters
can swing either way. So look at the original label and note if the
receive side is the higher of the two frequencies, or if the transmit
side is... and keep the high / low relationship the same as
you retune it. You may end up using the original receive side as
your transmit side. Personally, I remove the factory "Receiver" and
"Transmitter" labels and replace them with my own permanent labels reading "Higher
Side" and "Lower Side", then I add temporary "Receiver" and "Transmitter" labels
for each application. This is expecially true on GMRS (+ offset) and on amateur
UHF (- offset in southern California and many other areas).
The cable length between the cavities in a duplexer is very critical,
and the actual length of any one cable is dependent on both cable velocity factor
and frequency. On a UHF duplexer the optimum length is different between the receive
and transmit side. And the lengths of the cables between the duplexer ports
and the antenna "T" are also critical and frequency dependent. Many
duplexers are wider in frequency than their harnesses - for example if you move a
VHF duplexer from 150-174 MHz to 2 meters you will have to aquire a new
cable kit, or lengthen the old one. Hams that are moving a 470 MHz duplexer
will have the same problem.
Double-shielded silver-plated coax is the best thing to use to
connect duplexers. For example, RG-214 has two silver-plated braids
and a silver-plated inner conductor for maximum noise rejection. Avoid
coax types that have disimilar metals rubbing against each other such
as LMR-(any 3-digit or 4-digit number) or Belden 9913, both of
which use an aluminum foil shield rubbing against a copper braid. Many
amateurs have purchased LMR-400 or similar cable, installed it, and
it works fine (for a while). They just rave about how good it is. Then
anything from 9 months to 5 years later they find themselves taking it
down as the cable itself causes "duplex noise" (see the article titled
"Help!! I have a crackling noise in my repeater" by Kevin Custer
W3KKC in the Antennas section on this page). The expensive LMR cable
gets reused somewhere else. RG-142 and RG-400, both a
smaller version of RG-214 but sharing the same construction, can also
be used (but see the article on this page titled "Double Shielded Coax
Cable, The differences between RG-142 and RG-400, and why you DON'T want
to use RG-142..." by Eric Lemmon WB6FLY). My personal preference is to
use nothing but Heliax and Superflex on the antenna side of the duplexer,
and nothing but Superflex and RG-400 on the radio side. Yes, it's
expensive, but only once. It's going to last a long, long, long time,
and it's one less thing to worry about.
The cable length between the end cavity and the receiver or transmitter
is NOT supposed to be critical, and if it is on your system then you have an
impedance problem in the receiver or transmitter. The proper way to tune a
cavity or a duplexer is to use 6db or 10db 50 ohm pads between the test equipment
and the cavity or endmost duplexer can, as that ensures that pad "masks" any
non-50-ohm-impedance in your test equipment and ensures that the duplexer is
tuned to 50 ohms.
The attached feedline is 50 ohms, and the receiver or transmitter is SUPPOSED
to be 50 ohms. If it is not, the most common way to "fix" the problem is
to use a "magic" length cable - but the right way is to fix the radio so it
is 50 ohms. Some radios can't be fixed easily (but a Z-Matcher helps), so a
good way is documented here: Cabling
lengths between the Duplexer and Radio Set.
NEVER EVER LIFT OR CARRY A DUPLEXER BY THE HARNESS.
Despite the fact that your UHF duplexer is the right size the harness is not a
suitcase handle (if you need one use a piece of rope). The cable(s) in the
harness can be easily stretched, which changes the dimensions and velocity
factor, which changes the duplexer tuning and the system performance.
And never allow a cabling situation where there is tension (i.e. continuous
strain or load) on any cable in the harness. Look up "cold flow"
(pertaining to plastics), and then think about the center conductor of the coax
slowly migrating (moving) from the center of the coax to right adjacent to the
shield, and how that would affect the cable impedance at that location.
LIKEWISE, THE CAVITY TUNING RODS ARE ADJUSTMENTS
AND NOTHING ELSE
Never carry or support your duplexer by the tuning rods. Treat the whole assembly
as if it's as fragile as an eggshell. If it's a high band unit use the
factory design for the mounting frame. If it's UHF, 900 MHz or
1200 MHz mount it by the rack ears. If it's low band you are on your
own - but treat it gently.
A note on small mobile duplexers from Eric Lemmon WB6FLY:
(Most "mobile duplexers" are notch-only, and are sometimes called notchplexers)
Most UHF mobile notch-only "flatpack" duplexers will work fine below 50 watts
at a 5 MHz split- but their performance rapidly deteriorates when operated
outside of their stated band limits. For example, a commercial-band mobile
duplexer that was manufactured to operate in the 450-470 MHz band will
likely perform poorly in the 440-450 MHz Amateur band. Although such a
duplexer may SEEM to be working in the Ham 70 cm band, it may have excessive
insertion loss that the owner may not realize. That's because the internal
coupling loops are set at the factory during manufacture and not readily
adjustable by the owner.
I once tried to use a commercial-band mobile duplexer on 70 cm in a portable
repeater, and was disappointed in its performance- especially receive
sensitivity. I then ordered a new Celwave duplexer of the same model, but
factory-tuned for my Amateur pair. What a difference! Once the new
duplexer was installed, the range of the portable repeater was significantly
improved, with no other changes.
Other people report no problems with moving flatpacks to 440 MHz or even 420 MHz.
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DUPLEXERS - An Introductory Tutorial by Jack Daniel KD6YVL (offsite link)
This is a nice writeup that should be titled "Duplexers 101". Well worth reading.
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Theory and Testing of Duplexers by Jacques Audet VE2AZX
This is a large (60 pages) technical writeup that should be titled "Duplexers 102". Again, well worth reading.
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Technical Duplexer Page with good theory and explanations, and some homebrew construction notes. By John Portune W6NBC
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Understanding, Maintaining & Re-Tuning Antenna Duplexers 145kb PDF By William F. Lieske, Sr., Founder, EMR Corporation
A good basic theory writeup, including the differences between Band Pass and Band Reject. The original copy at the EMR web site
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Combating Spurious Output And Overloading With Cavity Filters 1.2mb PDF by TX-RX Corp.
A "Seminar Series" writeup that covers the theory behind cavity filters - mandatory reading for those unfamiliar with them.
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Coaxial
Resonators, Applied theory and practice, with photos by Mike
Pinfold, ZL1BTB
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Interference Control Through The Use Of Cavity Filters And Ferrite
Isolators 900kb PDF by TX-RX Corp.
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Technical Notes on Duplexer Problems and Remedies 1mb PDF By TX-RX Corp.
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A Guide to Duplexer Specifications over 130 different models, by Paul Kelley N1BUG (Contributions to the list are very welcome)
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Tuning and Adjusting Vari-Notch-Duplexers 185kb PDF by TX-RX Corp.
A "Seminar Series" writeup that covers the theory behind cavity filters and isolators.
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T-Pass Expandable Cavity Muticoupler System 500kb PDF by TX-RX Corp.
A "Seminar Series" writeup that covers the various type of cavity-based multicouplers and the T-Pass design.
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The Hybrid Ring
Duplexer A comprehensive explanation of the Hybrid Ring, by Kevin Custer W3KKC
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Six Meter Heliax Duplexer
Design by Jim Poll, WB5WPA (off-site link)
Here's one implementation of the above
design by Oscar KF6YB (off-site link)
Here's another implementation of the above design by Mike Perryman K5JMP (off-site link)
Six Meter Heliax Receive Filter Construction and Testing article based on the above designs, by Robert Meister WA1MIK and David Malicki N1OFJ. Note that this is NOT a full duplexer; just the receive half.
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Using open stubs to notch interference By Nico PAØNHC
(offsite link)
An excellent article on reducing paging transmitter (and others) interference into 2m repeaters.
Note that common European usage is that a comma is used where Westerners use
a period to mark decimals, for example 144.550 MHz is written as 144,550 MHz so readers
used to the period will have to do some mental "translation". In this article
Nico has used a mix of both forms so it can be a little confusing on the first read.
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GE Datafile Bulletin 10002-1,
A 25-250 MC Quarter Wave Stub Filter General Electric produced several useful DataFile Bulletins (the ones we have are available for free download from the GE LBI page at this web site). This one is a 400KB PDF file, and is subtitled:
"Even though General Electric Two Way Radio Transmitters well exceed FCC requirements for spurious radiation, the 60-80-db sprious attenuation provided may, in a few situations, be insufficicient to provent interference. This bulletin describes the construction of a filter, useful for supressing spurious radiation at one specific frequency...." |
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Someone say 6 meter duplexer? A
comprehensive conversion of a lowband pass cavity to BpBr by Jeff DePolo WN3A...
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How do I tune this notch duplexer? by Kevin Custer W3KKC
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A Homemade Duplexer for 2-Meter Repeaters by John Bilodeau, W1GAN (from the July 1972 QST magazine)
Note: In the 30-plus years since this article was written, the spring-contact based
BNC has fallen out of favor. Type N connectors are much preferred over BNC
connectors as they depend on a silver-to-silver screw compression contact, plus they
can handle more power. You must use double shielded coax in the
harness. RG-55 is mentioned in the article, I'd use RG-400 and compensate on
the inter-cavity lengths. If anybody has built this unit with better connectors
and modern cable, and would like to update this article please let me know.
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Tests of the DCI VHF and UHF 4-pole
bandpass filters by Robert W. Meister WA1MIK
These filters definitely do the job, meeting or exceeding manufacturer's specs. They cover the
entire 144-148 and 440-450 MHz bands and have sharp cutoffs. If you need more filtering,
they also sell 6, 8, and 10-pole filters with attenuations over 80dB. These handle 200 watts
and can be used at repeater sites.
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Decibel Products Click here for DB antennas
Data Sheet on DB's line of
power dividers - Three page PDF 264kb donated by John
Lock KFØM
This writeup
covers the K522 & K542 for 144-174 MHz, the K526 & K546 for 406-512 MHz,
the K528 & K548 for 800-960 MHz and the K528M & K548M for 1850-1990 MHz
DB's pipe and tower
mounting clamp kit DB365-OS Early
version donated by John Lock KFØM
DB's pipe and tower
mounting clamp kit DB365-OS &
ASPR616 (later version)
Installation
and Tuning Instructions for DB Band Pass Cavity Filters 50kb While this is oriented to the DB4001 (148-174 MHz),
DB4002 (118-512 MHz), DB4011 (70-88 MHz), DB4013 (88-118 MHz), DB4015
(118-148 MHz), DB4020 (406-420 MHz), DB4018 (225-400 MHz), DB4021
(406-512 MHz), DB4026 (406-512 MHz), DB4028 (806-960 MHz), DB4042
(30-50 MHz), DB4170 (138-174 MHz), DB4171 (450-512 MHz) models this
information is pretty generic information.
Field Tuning
Instructions for Dual Junction Tunable Isolators one-page 21kb
PDF file by Decibel Products
Tuning
Instructions for the DB4022 (UHF) & 4029 (800 MHz) band pass / band reject
cavities 31kb A two-page PDF file
DB
4023 UHF duplexer (3 cavity) and 4081 (4 cavity) spec sheet donated
by W. M. Kahl N6KYD
Tuning Instructions for the DB4030
(four cavity) and 4032 (six cavity) Low Band Duplexers five page
920Kb PDF donated by W. M. Kahl N6KYD
Tuning Instructions for
the DB4030 and 4032 4-cavity and 6-cavity Low Band Duplexers 24kb A two-page PDF file (appears to be a later version of the five page
one above)
Converting the DB-4032 Low Band Duplexer
to the 6M Amateur Band 29kb image A
one-page writeup from DB Engineering on converting the DB-4032 to the
6-meter amateur band It's a scan of a fax so it's not perfect,
but it's quite readable (oriented for printing)
Same drawing sized to be printed on 11x17
paper Both donated by Chris Nicholson N9LLO
Installation
and Alignment Instructions for the DB4036 (mid-band), 4044 and 4046 (high-band) Base
Station Duplexers 47kb
A two-page PDF file describing wide-spaced (3 MHz and 5 MHz) duplexers that
are not of much use to hams, but would be to public safety and disaster services folks.
DB
4048 duplexer specs (high band - 146-174 MHz) - an eight page PDF file
DB4048 duplexer review article
from June 1975 QST magazine - Page 1
Page 2
Scan courtesy of Glenn Little WB4UIV
Installationa and Tuning
on Decibel Products 4057 (three cavity) and 4058 (four cavity) high band duplexers Two page 120kb PDF donated by A. Nony Mous
Installation and Tuning Instructions for the DB4055 & 4056 (high band), 4067 & 4068
(406-420 UHF) and 4071 & 4072 (450-470 UHF) duplexers
40kb A two-page PDF file
Here's a photo of the internals of a 4072 housing.
Catalog sheet on the DB4060 & 4062 Band
Pass / Band Reject duplexers 55kb PDF
Installation and Tuning Instructions for
the DB4060 & 4062 Band Pass / Band Reject duplexers 46kb A
two-page PDF file (the DB4060 has 4 cavities, the 4062 has 6 cavities)
Repair of the DB4060 & 4062 Band Pass / Band Reject
duplexers 46kb An article by Bernie K5BP detailing notch
capacitor replacement for these units, including a source for the original component.
Repair of the DB4060 & 4062 Band
Pass / Band Reject duplexers An offsite web page by
N1BUG... he writes:
I have a DB-4062, which is the 6 cavity version of the 4060. It was old when I placed
it in service in 1997 but worked OK. Over the years it just slowly deteriorated until it
became essentially unusable. Finally I took the thing apart to investigate, and was able
to restore it to excellent function after 15-20 hours of work. I created a web page that
covered my experience...
Specifications and Data on the DB4075 and DB4076
UHF Bandpass Reject duplexers Photo 423kb
Tuning and Installation Information on the DB4075
and DB4076 UHF Bandpass Reject duplexers 91kb
Tuning Information on the DB4090 806-960 MHz
Bandpass Reject duplexers 43kb
Installation
and Tuning Instructions for the DB4104 (low band), 4040 (high band) and
4075 (UHF) single-cavity notch filters 25kb A
two-page PDF file
Installation
and Tuning Instructions for the 4307, 4308 and 4309 Hybrid Couplers
14kb PDF file.
Installation
and Tuning Instructions for the DB4318H-2C Single Channel Filter and Isolator 10kb A two-page PDF file describing a 164-168.5 MHz unit but
the directions apply to similar units.
Motorola
Info on the T-1480 series high
band 4-can duplexer / cavity filter panel 1.14Mb PDF file
of the official Moto manual that covers the two-cavity and four-cavity models (1481,
1482, 1485A, 1485AF, 1487A, 1487AF)
Info on the T-1500 series UHF
4-can duplexer / cavity filter panel There's
quite a bit of info, so it has it's own web page
Phelps-Dodge
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PD-506 manual 263 Kb
PDF Donated by Allan Crites WA9ZZU, scanned by Eric Lemmon WB6FLY
NOTE: You CANNOT tell from the model number if a PD-506 is for 144-174 or for
220-225 MHz ! You have to look at the frequency label !
This is a 4-cavity pass-notch duplexer than is supplied as either a 144-174 or
220-225 MHz version. At high band it will work from 600 KHz to 7 MHz
separation, and at 220 it will work at from 1 to 5 MHz separation. Rejection
is specified at 80 db, and under 2 db insertion loss.
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PD-522-509
Does anyone have the spec sheet, the tuning instructions or can supply a couple of photos?
This is a popular 6-cavity UHF duplexer that is built as a 4+2 unit (i.e. four cavities on one side and two on the other. If you set it on the table so that the single coax connector is on the left, and the two are on the right, the layout is in the sequence of:
TXnotch--cable--RXpass--cable--RXpass--cable--TXnotch--cable--RXnotch--cable--TXpass, with the first 4 cavities on the receive side and the last two on the transmit side.
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PD-638-509-6 manual 263 Kb
PDF Donated by Allan Crites WA9ZZU, scanned by Eric Lemmon WB6FLY
This is a 6-cavity pass-notch mobile duplexer that is available as a 150-162, 162-174,
220-225, or 471-512 MHz unit.
- 150-162 or 162-174 MHz: 150 watts, 75db rejection, 1.2 dB insertion loss at 2 MHz
spacing. At 5 MHz the insertion loss drops to 0.7 dB.
- 220-225 MHz: 100 watts, 75db rejection, 2 dB insertion loss at 1.6 MHz spacing.
- 470-512 MHz: 75 watts, 75db rejection, 1.7 dB insertion loss at 3 MHz spacing.
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PD5042-1 VHF Duplexer data from
Motorola 960 Kb PDF scanned by Eric Lemmon WB6FLY
Motorola duplexer 0185417U01 covers 132-146 MHz, 0185417U02 covers 144-160 MHz, and
0185417U03 covers 158-174 MHz. These are all based on the Celwave model PD5042-1-50
duplexer that can be ordered for VHF Quantar or MTR2000 stations.
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PD-7540, PD-7560, PD-7640,
PD-7660 duplexer manual 109 Kb This unit is also called the
"MiniPlexer".
This is a UHF flat-pack mobile notch-only duplexer that is limited to 40 watts and comes
in two ranges: 406-435 and 435-470 MHz and in 4 can or 6-can versions (7n40=4-can,
7n60=6-can). The 4-can version provides 50 dB rejection and 1 dB insertion loss at
5 MHz spacing, and the 6-can version provides 75 dB and 1.3 dB. Like any notch-only duplexer, any frequency outside the notches rides right through... Donated by A. Nony Mous.
PD-7540, PD-7560, PD-7640, PD-7660
duplexer manual 518 Kb
This is a later verion of the same manual, with enough new information to be worth having
both versions available. Donated by Allan Crites WA9ZZU, scanned by Eric Lemmon WB6FLY.
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Sinclair Labs
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P-Series Duplexer Specifications Sheet Covering
the P-1C01-G, P-1C02G, P-201G, P202G, P203G, P-301G, P-302G, P-303G models by
Sinclair Corporation.
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Sinclair 202-G cable harness drawing
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Tuning instructions for "P" and "Q" series cavity duplexers,
and FP, FR, FQ series cavities manual CM-1008 by Sinclair Corporation.
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Tuning instructions for the Q-202G, Q-208G,
Q-218G, 2B02G, Q-2B02G, Q-2B17G series cavity duplexers manual
FP-1032 by Sinclair Corporation.
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Catalog sheet and Specifications
for the 6-cavity Res-Lock Q-Circuit VHF Duplexer
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Tuning instructions for the Q-Series,
ResLok 4 - Q‑circuit Duplexers - manual number CM-351.
Written on the front is "Sincl Q2330E"
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Installation and Tuning instructions for the Q‑Circuit
Res-Lock Duplexers - manual number CM-1009.
This manual covers the Q-1220E (66‑88 MHz), Q-2220E (132‑174 MHz), Q-2222E (148‑174 MHz), Q-3220E (406‑512 MHz) and Q-4220E (806‑960 MHz) duplexers.
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Duplexer Tuning Instructions for the R101G
to R116G and R-1C01-G, R-1C02G, R-1A01G models (manual
number CM-159):
Note: This manual also covers a large number of other models in the 2H-30,
2H-37, 2H-43, 2H-66, 2H-77, H-30, H-37, H-43, H-66 and H-77 series. The
actual list is on the first page.
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Modification of R101, R104, or R110 for
amateur 6 meter operation (manual number CI-051).
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Hybrid Ring Duplexer Tuning Instructions
(manual CM-106) (theory on the W2EUP-designed Sinclair Hybrid Ring Duplexer).
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MR-354, MR-356 and MR-3332 406-512 MHz
mobile duplexer catalog sheet 191kb JPG file - scan of a catalog
page.
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Mobile duplexer MR-354 Specification Sheet 2-page
88kb PDF file donated by Ted Maczulat VE7TFM
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Mobile duplexer MR-356 Specification Sheet 2-page
87kb PDF file
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MR series mobile duplexer tuning (manual number CM 1010) 150kb JPG
file.
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SRL-101C Low band antenna information The sheet says "30-50 MHz" but gives info on 30-90 MHz. 440kb PDF file.
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SRL-229 High band antenna information |
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Epoxy Procedure 167kb PDF |
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Base Pipe 61kb
PDF |
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Installation Instructions 143kb PDF |
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Mounting Detail 92kb PDF
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"FP", "FR", "FQ" Series Bandpass Filters Product Description Page 1
34.2kb Page 2
28.9kb Donated by Eric Lemmon WB6FLY.
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"FP" Series Electrical
Specs 27kb PDF file donated by Eric Lemmon WB6FLY
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"FR" Series Electrical
Specs 31kb PDF file donated by Eric Lemmon WB6FLY
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"FQ" Series Electrical
Specs 30kb PDF file donated by Eric Lemmon WB6FLY
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"FP", "FR", "FQ" Series
Tuning 48kb PDF file donated by Eric Lemmon WB6FLY
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"FP" Series Tuning 61kb
PDF file donated by Eric Lemmon WB6FLY
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"FR"
Series Tuning 68kb PDF file donated by Eric Lemmon WB6FLY
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"FQ"
Series Tuning 71kb PDF file donated by Eric Lemmon WB6FLY
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"FP",
"FR", "FQ" Series Parts 23kb PDF file donated by Eric
Lemmon WB6FLY
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"P",
"Q", "R" Series Description 37kb PDF file donated by
Eric Lemmon WB6FLY
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"P" Series Electrical
Specs 40kb PDF file donated by Eric Lemmon WB6FLY
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"Q" Series Electrical
Specs 41kb PDF file donated by Eric Lemmon WB6FLY
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"P" and "Q" Series
Preliminary Tuning 32kb PDF file donated by Eric Lemmon WB6FLY
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"P" and "Q" Series
Outlines 42kb PDF file donated by Eric Lemmon WB6FLY
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"P" Series Retuning 58kb
PDF file donated by Eric Lemmon WB6FLY
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"Q" Series Tuning 86kb
PDF file donated by Eric Lemmon WB6FLY
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"P" and "Q" Series Parts 33kb
PDF file donated by Eric Lemmon WB6FLY
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"C" Series Description 53kb
PDF file donated by Eric Lemmon WB6FLY
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"C" Series Systems 79kb
PDF file donated by Eric Lemmon WB6FLY
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"C" Series Electrical
Specs 59kb PDF file donated by Eric Lemmon WB6FLY
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"C" Series Mechanical
Specs 64kb PDF file donated by Eric Lemmon WB6FLY
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"C" Series Curves 49kb
PDF file donated by Eric Lemmon WB6FLY
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"C" Series Typical Systems 67kb
PDF file donated by Eric Lemmon WB6FLY
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"C" Series Tuning 49kb PDF
file donated by Eric Lemmon WB6FLY
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"C" Series Parts 71kb PDF
file donated by Eric Lemmon WB6FLY
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| Telewave |
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TPRD-series Duplexer Tuning
Instructions 50Kb PDF file donated by A. Nony Mous
Generic tuning instructions for their pass/reject duplexers. |
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TPRD-1554 & 1556
Duplexers 92Kb PDF file donated by A. Nony Mous
These are VHF pass-reject duplexers good for 350 watts. The TPRD-1554 is VHF 4 cavity
and the 1556 is 6 cavity. |
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TPRD-4544 & 4744
Duplexers 104Kb PDF file donated by A. Nony Mous
UHF 4 cavity pass-reject, 250watts. The 4544 model is for 400-470 MHz, the
4744 is for 470-512 MHz. |
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TPRD-9044 Duplexer 88Kb PDF file
donated by A. Nony Mous
890-960 MHz 4 cavity pass-reject, 250 watts
If 4 cavities are enough in your RF environment then this is an ideal unit for 900 MHz
amateur repeaters. |
| TX-RX |
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Overview of
TX-RX Low Band Duplexers 2 mb PDF Also has
some Tech Aid documents |
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Overview of TX-RX
High Band & 220 MHz Duplexers 2 mb PDF
Includes a chart explaining their model numbering system
Hint: The center digit pair are the magic numbers:
13=30-40 MHz, 14=38-50 MHz, 29=88-108 MHz, 36=132-150 MHz, 37=144-174 MHz, 38=132-174 MHz, 41=148-174 MHz, 52=215-250 MHz, 65=406-430 MHz, 66=442-450 MHz, and 97=1215-1300 MHz. |
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Data Sheet on the TX-RX
model 28-37-02A 144-175 MHz duplexer 2.7 mb PDF
If a 4-cavity model is enough for your situation, this is the ideal model for a 2m
repeater - it will handle 400 watts at 500 KHz spacing with 85 db of
isolation. Otherwise look at the 28-37-11, it's the 6-cavity version with
100 db. |
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Instruction Manual
Vari-Notch Duplexers (6" Cavities) 189 kb PDF
While this is a generic manual on the TX-RX duplexers it contains a chart saying
it pertains to the following units:
28-13-01F (30-40 MHz),
28-14-01F (38-50 MHz),
28-28-02A/G (66-88 MHz),
28-36-02A/G (132-150 MHz),
28-36-11E/G (132-150 MHz),
28-37-02A/G (144-174 MHz),
28-37-11E/G (144-174 MHz),
28-37-08G (144-174 MHz),
28-65-01A (406-430 MHz),
28-65-05A/G (406-430 MHz),
28-70-01A (450-470 MHz),
28-70-07A/G (450-470 MHz),
28-69-01A (470-512 MHz),
28-69-04A (470-512 MHz)
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Wacom At some point Wacom was bought by Remec, and
in November of 2001 was sold to TX-RX.
Notes on the Wacom WP-641 BpBr
Cavity by Kevin Custer W3KKC
Field Tuning Instructions
for Wacom WP-604, WP-609, WP-612, WP-621, WP-629, WP-639 and WP-641 VHF
Duplexers donated by Eric Lemmon WB6FLY
Field Tuning Instructions
for Wacom WP-678-R2 and WP-665-R2 UHF Duplexers donated by Eric
Lemmon WB6FLY
Spec Sheet for WP-604 (low band, 4-cavity) 371kb PDF
Spec Sheet for WP-621 and WP-641 (high band, 4-cavity) 218kb
PDF
Spec Sheet for WP-623 and WP-643 (high band, 6-cavity) 178kb
PDF
Spec Sheet for WP-629 and WP-639 (high band, 4-cavity) 188kb
PDF
Spec Sheet for WP-652 and WP-653 (220mc, 4-cavity) 248kb PDF
Spec Sheet for WP-665 and WP-678 (UHF, 4-cavity) 215kb PDF
WP-687-3943 Catalog Sheet (900 MHz, 4-cavity) 145kb GIF
WP-687-3943 Spec Sheet (900 MHz, 4-cavity) 1.65mb PDF
WP-687-3943 Test Sheet (900 MHz, 4-cavity) 1.35mb PDF
WP-687-3943 Field Tuning Instructions (900 MHz, 4-cavity) 409kb PDF
WP-4941-7941 Spec Sheet (900 MHz, 2-cavity) 2Mb PDF
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Antennas and Towers
Repeater owners have favorite antennas - some prefer colinear antennas ("fiberglass sticks"), others prefer dipole arrays. Personally I prefer grounded dipole arrays. Colinear antenas are more prone to duplex noise (see the "crackling" article below), dipole arrays can have phasing harness degredation. Picture four loop dipoles side mounted on a steel mast. Suddenly one day you notice that the coverage has gone to hell. When you check the antenna with a SWR bridge you discover that you still have a 1:1 SWR. Phasing is the key concept here. The RF is fed to the dipoles by means of a cable harness of critical-length coaxial lines that accomplish both the phasing of the dipoles and RF power division. The VERTICAL pattern of the antenna is determined partly by the RF phase relationship between the dipoles. When the antenna is new, the phase relationships are perfect. As the antenna ages, moisture can infiltrate the coax and connectors. Coax dielectric can begin to deteriorate. This will slowly cause the vertical pattern (and gain) of the antenna to change. A perfect SWR does you no good when your RF power is going straight up in the air or straight down into the ground! So if you use a dipole array then you want to be an annoying perfectionist about the phasing harness.
And as said above, don't go cheap on the antenna or feedline. You can have the best sounding repeater on the planet, but it's both worthless and useless if the users can't get into it or hear it because you used a Ringo Ranger and RG-213-type feedline (don't laugh, I've seen it).
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Radio Antenna Engineering By Edmund A. Laport This is a 1952 textbook and the original copyright has expired. The PDF file is 38.5 Mb. At the time, Mr. Laport was the Chief Engineer of RCA International Division. While the book is oriented towards antennas up to 30 MHz, the Preface is worth reading (4 pages) as theory doesn't depend that much on wavelength. The Introduction (11 pages) has some math, but it's also very interesting. |
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The W1GHZ Online Microwave Antenna Book By Paul Wade W1GHZ (ex N1BWT) An excellent text, and worth reading. (offsite link) |
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Antenna Design for
Omnidirectional Repeater Coverage By James Ruxlow N9SN
What do you do when you need omni coverage, and you have to side mount the
antenna to a triangular tower that is over fifteen feet on each face? The
Western Illinois ARC figured it out. And their solution works well.
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Precipitation Static and Duplex Radio... The Phenomena and the Cure! Rain and snow clouds contain more than rain and snow By Kevin Custer W3KKC.
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Help!! I have a crackling noise in my
repeater Why it's there and how to cure it... By
Kevin Custer W3KKC.
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Vertical and Horizontal antenna separation
charts Provided by Kevin Custer W3KKC.
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440 MHz Folded Dipole Repeater Antenna (222kb PDF file) This is a two page PDF file of the classic 73 Magazine construction article by Chuck Kelsey WB2EDV - Yes, you can build yourself a DB-224 folded dipole array.
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Information on a Cycloid Dipole (also known as circular polarization) antennas By the WA7X crew (offsite link)
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"Calculating Downtilt" by Scala Division of Kathrein Corp (Technical Bulletin #112) 39kb PDF
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Omni-Directional Gain Vertical Collinear Construction Project By Mike Collis WA6SVT
Yes, you too can build a Stationmaster - for any frequency from 2 meters to 1.3 GHz
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Some variations and constructions ideas on the WA6SVT collinear by Kevin Custer W3KKC
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One ham's experiences with the WA6SVT antenna by Paul Kelly N1BUG
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Here's the construction article promised in
the above article by Paul Kelly N1BUG
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Build A 9 dB, 70cm, Collinear Antenna From Coax By Michael Martell N1HFX (offsite link)
Yes, you can build a decent home base station antenna from RG-58 coax.
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Cheap Yagi Antennas for VHF/UHF By Kent Britain, WA5VJB for the Clear Lake Amateur Radio Club of Houston, Texas.
This article describes a easy-to-build inexpensive yagi (beam) antenna that can be built for 2m, 220, 440, 900 or 1296 MHz.
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A Copper Cactus Dual-Band J-Pole Antenna Project By Tony Petersen N7QVC
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Fiberglass Antenna Painting
Procedure by Celwave Corp., provided by Mike Dees N3EZD See the next article as well.
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Some Notes on Fiberglass Antenna Painting Comments from several folks that accompany the above article.
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Retuning a Stationmaster type antenna By Jim Barbour WD8CHL |
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How to look up a tower location Lists all FCC registered towers - broadcast, cellular, everything... (offsite link - to the Berkana server)
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Tower lookup page at the FCC web site (offsite link - to the FCC server)
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The Rohn Towers 2004
Catalog 38 Mb PDF file
This was sent in anonymously and it's a big download.
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Advanced Electronic Applications / AEA |
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For information on AEA antennas including the Isopole please see the AEA page. |
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| Decibel Products / RFS |
 |
IMPORTANT !! A letter suffix indicates the range that an antenna is built
for: 138-150 MHz, 150-160 MHz, 155-165 MHz, or 164-174 MHz but that the lettering is NOT
consistent across the product line, nor is the actual frequencies. For example, on
one product (i.e. one model number) an "A" model might be 150-159 MHz, while on
another an "A" model might be 150-155 MHz. While in many cases an "A" range is
the one that starts at 150 MHz, it can vary with EACH antenna model number: one
antenna might have "A" be the 138-150 MHz range, and another might have "E" be
the 138-150 MHz range. Be very careful that you check your range letter
definition before you spend your money (on new or used antennas) ! |
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Data sheet on the DB201 ground plane omni
antenna 717kb PDF file
This is the so-called "bent-over" ground plane that comes
in two models: one for 30-174 MHz and the other for 220-512 MHz. |
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Cutting chart for the DB-201 Page
1 159kb Page
2 111kb Courtesy Russ Stafford W3CH |
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A poor scan of the data sheet on the DB-212 side mount omni antenna (33-88 MHz)
Page 1 260kb Page 2 203kb Drawing of the diagram on Page 2 34kb
Here's the Andrew version of the same catalog sheet (and a much better scan), courtesy of Allen Wilde N1IOE
and here's the DB-212 tower mounting instructions, also courtesy of Allen Wilde N1IOE |
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You can move a low band DB212 to 6m by basically freeing up the trombone section of the antenna, adjusting the postion, then locking it down again. Just measure the current length of the dipole and then multiply this length by (current-freq divided by the new-freq). So if
the current length is 184 inches and the current freq is 46 MHz and your destination frequency is 52.5 MHz the new length (in inches) is therefore 184*(46/52.5).... To change the length you will need to remove the pop-rivet and a little dimple that the production line uses to hold the trombone in place until the rivet is installed. Sometimes the VSWR depends on the tower face. If you want to super tune the antenna set the antenna up on a tower leg several feet off
the ground, preferrably a little over a 1/2 wave if you can do it. Then adjust the trombone to the length you calculated and apply a little RF power and check the reflected power. Then get a long stick and start moving the trombone slowly while watching the reflected power. When you get the best possible VSWR, stop and redo the rivets. Personally I'd add a bead of non-acidic silicone bathub sealer to water-seal the joint.
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Detailed measured diagram of the low-band four-element
DB-212 wiring harness Courtesy Bill Cotter N4LG.
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WA1ZYX's web page about modifying the
DB-212 elements for 6 meters Off-site Link.
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DB-224 catalog data (PDF files): Decibel DB224
Data Sheet 156kb Andrew DB224
Data Sheet 140kb DB224
Instruction Sheet 153kb
Here's the instruction sheet that comes in the box with the
DB-224 Page
1 964kb Page
2 1,032kb Page
3 819kb Courtesy John Lock KFØM.
The DB224 is the standard antenna that all other 2m / high
band repeater antennas are measured against. These guys cost a little more than a
fiberglass antenna but will easily last 20-30 years, and don't have the cracked joint duplex noise problem, nor will you have a pile of fiberglass toothpicks on the ground after a nearby lightning strike. How
many Hustler, Comet or Diamond antennas will you go through in 20-30 years?
The DB-224 is rated at 80 MPH winds, but that's wishful thinking unless you side mount
it with clamps on BOTH the top AND the bottom. Frankly, chosing to mount your antenna on the tower top only to get a few extra feet isn't worth a bent or broken support tube, and if your
antenna is side mounted the tower itself (or someone else's antenna) can be the lightning rod and take the hit.
Note that all "DB-224"s are not the same... they may all be tower-mounted exposed
dipole arrays with 6 to 8db of gain (depending on the pattern), it's the suffix letter that
is important:
- the DB224-A model is 150-160 MHz circular pattern,
- the DB224-B model is 155-165 MHz circular pattern,
- the DB224-C model is 164-174 MHz circular pattern,
- the DB224-E model is 138-150 MHz circular pattern (but try and find one second hand...),
- the DB224-FAA model is 127-141 MHz circular pattern (it can be shortened to 2m),
- the DB224-F model is 160-170 MHz circular pattern,
- the DB224-J model is 276-285 MHz circular pattern,
- and the DB224-JJ model is 220-225 MHz circular pattern,
- the DB224E-A model is 150-160 MHz offset pattern,
- the DB224E-B model is 155-165 MHz offset pattern,
- the DB224E-C model is 164-174 MHz offset pattern,
- the DB224E-E model is 138-150 MHz offset pattern (again, try and find one second hand...),
- and the DB224E-JJ model is 220-225 MHz offset pattern,
- The DB224 series can be ordered as a single or dual antenna. Just modify the model number by adding an "S" in the right spot - a DB224-JJ single antenna becomes a DB224S-JJ as a
dual antenna. It amounts to separating the elements into two independent antennas on the same mast. Each antenna has a separate feedline terminated at
the bottom of the mast. A DB224ES-A or DB224ES-JJ is a dual antenna with the offset pattern.
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A detailed drawing of the DB-224-A and
DB-224-E 104kb PDF file A 2-page PDF donated
by Skipp. Note that the element length measurements are shown for both the
"A" (150-160 MHz) range and the "E" (138-150 MHz)
range. There is enough information here that anyone with some experience bending
aluminum tubing can build one for themselves.
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Another detailed drawing of the
DB-224-E 60kb PDF file Donated by Doug Zastrow WBØUPJ. Note
that the element length measurements shown in the diagram are for 136-150 MHz frequencies.
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Conversion calculations for moving your DB224
to a different band split. 90kb PDF file All of the magic calculations
plus coax types necessary to redo your DB224's wiring harness and set the element length
and spacing.
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DB-228 catalog data (PDF files): DB228 Data
Sheet 87kb DB228
Instruction Sheet 60kb
Here's the instruction sheet that comes in the
box with the DB-228 772kb PDF Courtesy John Lock KFØM
Note that on this antenna an A suffix indicates 150-160 MHz, B=155-165 MHz, C=164-174 MHz
and E=138-150 MHz.
The DB-228 is essentially two DB-224s on one 41-foot long mast, and can be ordered with a
phasing harness that makes it one antenna - and that makes it the ultimate 2m repeater
antenna (10 to 12db depending on the pattern). The catalog sheet shows the "normal"
mounting has being a split mount: the top half is above and the bottom half is below the top
of a tower (i.e. the bottom half is side mounted with two clamps at the middle and bottom);
however, unless you want to be the lightning rod the DB228 can be fully side mounted with
the two brackets at top and bottom, or an optional third bracket can be added in the middle
(I certainly would, especially in any area that has a problem with antenna icing).
Or if you need extra RX-TX separation: order it with the -S (split kit) option and use it
with two feedlines and a split duplexer as separate DB224 receiving and transmitting
antennas. |
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DB's installation instruction sheet on the
DB-264 155kb PDF Courtesy of Paul Kelly N1BUG
The DB-264 is a 4 element dipole array that is constructed for any 10 MHz segment of 150-285 MHz. This is the model that has the feed harness hidden inside the
support pipe. I've seen one of these on 224 MHz, and it's rugged!
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DB's instruction sheet on the DB-314
114kb PDF Courtesy A. Nony Mous
The DB-314 is essentially a 8 UHF dipoles (a DB-408,
6.6db gain) and 4 high band dipoles (half of a DB-304, 3.2db) on the same
mast, with separate feedlines. If you need a commercial grade
dual band antenna, this is it. Or if you are limited to one
antenna, then order this guy and use it as separate 2m and 440 antennas
with two feedlines, or with a pair of commercial-grade TX-RX Corp. "diplexers"
that put both antennas on one feedline. But don't try and use one on a
147.09 MHz; repeater paired with a repeater whose input
is 441.275 MHz (do the math... and it dosen't matter what
antenna you have in that situation) |
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The DB404 UHF dipole array is two pairs of UHF dipoles mounted to a mast. Here
is the factory data: (PDF files) DB 404 Data Sheet 93kb DB 404 Instruction Sheet 131kb |
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DB404 UHF dipole array (JPG files) Page 1 879kb Page 2 568kb |
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A detailed drawing of the
DB-404-B Donated by Skipp. Note that
the element length measurements shown in the diagram are for 450-470 MHz
frequencies. |
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A detailed drawing of the
DB-404-D Donated by Skipp. Note that
the element length measurements shown in the diagram are for 488-512 MHz frequencies. |
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The DB-408 is essentially two DB404s stacked on one longer mast (almost 9.5 feet long)
and can be ordered with one or with two feedlines (the "split kit"). Specify Omni
or Offset pattern when ordering, and if top or side mounting when ordering. For side
mounting order the DB5012 mounting kit.
Here is the DB408 UHF dipole array factory data: DB408
Data Sheet 93kb DB408
Instruction Sheet 80kb (PDF files)
On this antenna the power limit is 250w, the frequency range A = 406-420,
B = 450-470, C = 470-488, D = 488-512.
The "E" range is either 482-494 or 440-450 depending on which catalog you read,
be very, very careful when ordering one.
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A detailed drawing of the
DB-408-B 300kb Donated by Skipp. Note that the element
length measurements shown in the diagram are for 450-470 MHz frequencies. |
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DB411 UHF dipole array factory data: (PDF files) DB 411 Data Sheet 75kb
DB 411 Instruction
Sheet 217kb
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A detailed drawing of the DB-411-B 25kb
PDF Donated by Skipp. Note that the element length
measurements shown in the diagram are for 450-470 MHz frequencies. |
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The DB-420 is essentially two DB408s stacked on one longer mast and can be
ordered with one or with two feedlines (the "split kit"). Specify Omni
or Offset pattern, and if top or side mounting when ordering.
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A drawing of the DB-420-B phasing harness 140 KB PDF
This is the 450-470 MHz version. Anybody have a drawing for 440-450 MHz ?
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The data sheet on the DB420 UHF dipole
array 113kb PDF file The DB420 is an array
of 8 dual dipoles that can be configured as a single 8-element antenna or as
two 4-element antennas on the same mast (conversion requires a different
harness).
The DB420 UHF dipole array
Assembly and Mounting Instructions 145kb PDF
file
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Factory data sheet on the DB5004 / DB5030 Outrigger 378 KB PDF
This is the data sheet on the fiberglass outrigger that supports the Stationmaster and SuperStationmaster style fiberglass monopoles. I recommend one per 10 feet of antenna (i.e. you'd use two on a 21 foot SuperStationmaster). |
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Motorola |
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The 1964 manual for the TAD1000-series
coaxial VHF antennas donated by Skipp Description,
Installation, Assembly, Parts. 150KB PDF file
Covers the models TAD1001x, TAD1002x, TAD1003x, TAD1004x, TAD6071x, TAD6072x, TAD6073x, TAD6074x (where "x" is an "A" or a "B"). |
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VHF unity-gain antenna model information
and specifications for the TAD1010-series antennas donated by
Skip 255KB PDF file
More info on the 1001, 1002, 1003 and 1004 models listed above, plus info on the TAD1012x, TAD1013x, TAD1014x, TAD1021x, TAD1022x, TAD1023x and TAD1024x series (where "x" is an "A" or a "B"). |
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VHF 3dB-gain antenna model information
and specifications for the TDD602x-series antennas donated by
Skip 240KB PDF file
Covers the models TAD6021A, TAD6022A, TAD6023A and TAD6024A units. |
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VHF 5.5dB-gain antenna model information
and specifications for the Motorola branded Stationmaster style antennas donated
by Skip 268KB PDF file
This sheet covers the models TDD6071A, TDD6072A, TDD6073A, TDD6074A, TDD6075A, TDD6081A, TDD6082A, TDD6083A, TDD6084A, TDD6085A, TDD6090A, and TDD6100A. |
| Calculators (dBm / voltage,
intermod, fade margin, etc.) |
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Converting between dbm and millivolts or
microvolts A no-math graphical calculator it's
only a xerox copy of the metal rim of a attenuator wheel from a Measurements Corp.
Model 80 RF Signal Generator... but it's very handy. Courtesy of Ray Von
Neumann K6PUW
I suggest that you print this out and tape it to the front panel of your signal generator
that is calibrated in uV and mV only. Once you realize how dbM numbers work you will find
yourself referring to it on a regular basis. |
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Converting between dbm and
millivolts or microvolts A no-math tabular calculator (a lookup
table). The above xerox of the attenuator scale is easier to use. |
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dBm to Microvolts Conversion
Chart By IFR Corp. The above xerox of the attenuator scale
is easier to use. |
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An
online intermod calculator from AudioTechnica
Note that this is oriented to wireless microphones, but since
it handles up to 30 frequencies it is very handy. (offsite
link).
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Another downloadable intermod
calculator This one is shareware written by KE6QH. |
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This downloadable
calculator program figures intercept points and device intermod levels
This one is is from Kessler Systems Inc. (offsite link) |
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This online
calculator program from TCS Consultants, Inc. saves
the site description to a 'cookie' file on your computer. (offsite
link)
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Online
fade margin calculator program from TCS Consultants, Inc.
This is neat! (offsite link)
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FCC HAAT (Height
Above Average Terrain) Calculator (offsite link to the FCC web site)
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FCC Coordinate
Calculation Program (offsite link to the FCC web site)
This is a useful calcualtor for point-to-point links... "This program will calculate the end coordinates, in degrees, minutes and seconds, given an initial set of coordinates, a bearing or azimuth (referenced to True North or 0 degrees), and a distance...."
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FCC
Coordinate Conversion Program (offsite link to the FCC web site)
"This utility permits the user to convert latitude and longitude between decimal degrees and degrees, minutes, and seconds. For convenience, a link is included to the National Geodetic Survey's NADCON program, which allows conversions between the NAD83 / WGS84 coordinate system and the older NAD27 coordinate system. NAD27 coordinates are presently used for broadcast authorizations and
applications."
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FCC
Distance Calculation Program (offsite
link to the FCC web site)
"This program will calculate the distance and azimuth (referenced to True North) between two sets of coordinates on the earth."
The last four calculators above are courtesy of Dale Bickel of the USA Federal Communications Commission. The FCC also has a number of "Conversions" calculators including FM Channel to Frequency, FM Frequency to Channel, TV Channel to Frequency Band, Feet to/from Meters, Miles to/from Kilometers, dBu to/from mV/m,
kW to/from dBk, Relative Field, Transmission Line Efficiency, and more.
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An old DB Products DOS program that calculates down-tilt for antennas 128kb ZIP file |
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An old DB Products DOS program that plots some antenna
patterns 383kb ZIP file |
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An old DB Products DOS program that gives you some insight
into the effects of side-mounting vertical antennas 134kb ZIP file
The above three programs were supplied by Dave Gartner WD6AXM.
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Mobile Antennas
Hints: (1) Don't use solid center conductor coax on a mobile antenna (especailly on something that moves). (2) Punch-mounts are 20 times better than clamp-on-the-edge-of-the-trunk-lid mounts and 50 times better than magnetic mounts. If you have to use a mag mount use a 1/2 wave antenna intended for zero-ground-plane installations (like motorcycles).
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This web page created and first posted 14-Oct-2004.
Layout and hand coded HTML © Copyright 1995
and date of last update by Mike Morris WA6ILQ
This web page, this web site, the information presented in and
on its pages and in these modifications and conversions is © Copyrighted
1995 and (date of last update) by Kevin Custer W3KKC and multiple originating
authors. All Rights Reserved, including that of paper and web
publication elsewhere.
