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Antenna Systems Information (antennas, feedlines, duplexers, circulators, isolators, calculators, etc.) Compiled from a multitude of donations by Mike Morris WA6ILQ |
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 relevant data sheets, class handouts or other
information that we do not have here, please consider scanning
them and emailing us the scans.
If you don't have 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.
| Jump to: | System Engineering Antennas and Towers Connectors, Coax and Shielding Cavities and Duplexers |
| Combiners Isolators and Circulators Calculators Mobile Antennas |
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 - 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 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 putting up a repeater that will be used in 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 tools "buying quality only hurts once"). A good Sinclair 4-pole or 8-pole antenna will last over 20 years of serious winters. How many Comets or Diamonds will you buy 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 amplifiy 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. And before you put up a system measure the noise floor on your frequency at the site. 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 system will hear better. And with repeaters it all depends on how well you hear. Given the limits of antenna power rating and local geography, increasing the talk range is easy - how much amplifier and duplexer 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 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 situstion 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 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. But always have enough extra headroom in your duplexer to handle the situation that the site owner adds additional repeaters to the site, or that you want to add a preamp later on. If the duplexer is your primary provide of receiver-to-transmitter isolation do not scrimp on the duplexer. Next to 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), I use the six cavity pass/reject type exclusively. Duplexer tuning is 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 types, 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 radio site RF environments, especially duplex environments. While iDEN is a 900 MHz system the physics is the same at 28 MHz through 1296 MHz. 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. Yes, you'd expect that conclusion from the makers of Heliax, but there's a lot more to it than that. Worth reading. |
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Where exactly is your repeater? And are you really sure? Donated by Eric Lemmon WB6FLY |
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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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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 serious effects on antenna systems. |
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RF Communications - A Non
Technical Approach By Decibel Products Corp. 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 3 DB really worth it? The answer is "It Depends" By Neil Johnson WBØEMU |
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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 "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 |
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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 & 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 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. |
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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. |
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. 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 rahter complex subject has been attempted in an effort to bring about a better understanding of combiners used in two-way radio systems."
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 load (usually fairly low in power handling capability) so 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 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 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 commercial applications 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).
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) a 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. Contact information is on the suppliers index page.
The frequency "range" shown on the spec sheet for an isolator/circulator is really an indicator of the manufacturer's capability to build them, not the field tuning range of any one particular device. For example, once an isolator/circulator is made for a particular high band frequency, it can only be tuned a 3 to 4 MHz (figure about 3%) either side of that frequency. Once outside of that 6 to 8 MHz "window", it will cost between $200 and $300 to have an isolator or circulator remanufactured from (for example) a 165 MHz frequency to your specific 146 MHz frequency (or from 460 MHz to 440 MHz) because it involves a considerable amount of precision bench work using RF test equipment, mechanical tools and professional skills that very few shops or people have: copper or bronze vises (nonmagnetic) to position 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 device rebuilt by a person who does it 8 hours a day, and every day guarantees that it is done right the first time, is much cheaper than buying a new device, it comes with a factory guarantee and lands in your hand already tuned on your frequency with a warranty and some nice proof-of-performance plots. 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 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 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 repater) reported that the system went from its normal 90% quieting 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 installing 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 or circulator do it with low power - 2 to 5 watts, maybe 10 watts max. 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 & 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...
What's a circulator? a.k.a. Properties of
a Ferromagnetic Circulator By Kevin Custer W3KKC
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
The Care and Feeding of the R.F. Isolator a 14kb PDF by William F. Lieske, Sr. Founder, EMR Corporation
Sinclair's instructions on tuning
isolators Donated by Eric Lemmon WB6FLY
Microwave
Associates 7R011 Isolator Tuning Instructions 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. Donated by Micheal Salem N5MS
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 unit but
the directions apply to similar units
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.
Cavities, Duplexers, Power Dividers, Theory, and More
A duplexer is made up of a number of cavities, 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.
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 UHF, possibly VHF) receive on the higher frequency and transmit on the lower frequency, whereas amateur repeaters can go 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.
The cable length between cavities is critical, and is dependent on ferquency. And on a UHF duplexer they are different lengths 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.
| 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 | |
| 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 | |
| Interference Control Through The Use Of Cavity Filters And Ferrite Isolators 900kb PDF by TX-RX Corp. | |
| Technical Notes on Duplexer Problems and Remedies 1mb PDF By TX-RX Corp. | |
| A Guide to Duplexer Specifications over 130 different models, by Paul Kelley N1BUG (Contributions to the list are very welcome) | |
| 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 | |
| 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 Peryman K5JMP (off-site link) |
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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.. | |
| How do I tune this notch duplexer? by Kevin Custer W3KKC | |
| 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 RG400 and compensate on the lengths. |
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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. |
| Celwave Click here for Celwave antennas | ||
| Celwave model 696, 696SR (UHF), 896 or 896SR (800-960 MHz) Duplexer 86Kb PDF file Donated by Allan Crites WA9ZZU, scanned by Eric Lemmon WB6FLY | ||
| Celwave Duplexer Cable Harness Lengths (oriented for printing) 44Kb PDF file Donated by A. Nony Mouse | ||
| Decibel Products Click here for DB antennas
Here's a photo of the internals of a 4072 housing.
Motorola Phelps-Dodge
Sinclair Labs
Wacom At some point Wacom was
bought by Remec, and in November of 2001 was sold to TX-RX.
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Antennas and Towers
| Precipitation Static and Duplex Radio... The Phenomena and the Cure! Rain and snow clouds contain more than rain and snow By Kevin Custer W3KKC | |
| Help!! I have a crackling noise in my repeater Why it's there and how to cure it... By Kevin Custer W3KKC | |
| Vertical and Horizontal antenna separation charts Provided by Kevin Custer W3KKC | |
| 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. | |
| Information on a Cycloid Dipole (also known as circular polarization) antennas By the WA7X crew (offsite link) | |
| "Calculating Downtilt" by Scala Division of Kathrein Corp (Technical Bulletin #112) 39kb PDF | |
| Omni-Directional Gain Vertical Collinear Construction Project Yes, you too can build a Stationmaster - for any frequency from 2 meters to 1.3 GHz By Mike Collis WA6SVT | |
| Fiberglass Antenna Painting Procedure by Celwave Corp., provided by Mike Dees N3EZD See the next article as well. | |
| Some Notes on Fiberglass Antenna Painting Comments from several folks that accompany the above article | |
| Retuning a Stationmaster type antenna By Jim Barbour WD8CHL | |
| 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). The Introduction (11 pages) has some math, but it's also very interesting. | |
| The W1GHZ Online Microwave Antenna Book By Paul Wade W1GHZ (ex N1BWT) An excellent text, and worth reading. (offsite link) | |
| 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. |
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| The Rohn Towers 2004 Catalog 38 Mb PDF file This was sent in anonymously and it's a big download. |
| Advanced Electronic Applications / AEA | ||
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For information on AEA antennas including the Isopole please see the AEA page. | |
| Celwave | ||
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A detailed drawing by Skipp of the Celwave-built Motorola TDE6090A welded yagi beam antenna 69KB PDF file This is a two page PDF, the first page is Skipp's measurments, the second is the Celwave drawing. There is enough information here that anyone with a welder could make their own very strong winter-ice-proof welded 10db gain yagi antenna. Note that the element length measurements shown in the diagram are for 420 MHz frequencies. | |
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| Motorola | ||
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The 1964 manual for the TAD1000-series coaxial VHF antennas donated by Skip Description, Installation, Assembly, Parts. 150KB PDF file | |
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VHF unity-gain antenna model information and specifications for the TAD1000-series antennas donated by Skip 255KB PDF file | |
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VHF 3dB-gain antenna model information and specifications for the TDD6020-series antennas donated by Skip 240KB PDF file | |
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VHF 5.5dB-gain antenna model information and specifications for the TDD6070-6100-series antennas donated by Skip 268KB PDF file | |
| Connectors, Coax and Shielding | |
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| WA2ISE's chart of the specs of common coax cables By Robert Casey WA2ISE | |
| Another chart of the specs of common coax cables (offsite link) Courtesy of Coastel Cable Tools of Syracuse, New York | |
| Double Shielded Coax cable The differences between RG-142 and RG400, and why you DON'T want to use RG-142... by Eric Lemmon WB6FLY | |
| Shielding Effectiveness.... A 268kb PDF Document by Andrew Corp. covering the types and parameters of shielded cables. Original copy is here | |
| Installing PL-259 connectors on FSJ1-50A 1/4" Superflex Heliax a photo article by Tony King W4ZT | |
| 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 metal wheel copy is easier to use | |
| dBm to Microvolts Conversion Chart By IFR Corp. (the above metal wheel copy is easier to use) | |
| 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) | |
| Another downloadable intermod calculator This one is shareware written by KE6QH | |
| This downloadable calculator program figures intercept points and device intermod levels This one is is from Kessler Systems Inc. (offsite link) | |
| This online calculator program from TCS Consultants, Inc. saves the site description to a 'cookie' file on your computer. (offsite link) | |
| Online fade margin calculator program from TCS Consultants, Inc. This is neat! (offsite link) | |
| FCC HAAT (Height Above Average Terrain) Calculator (offsite link to the FCC web site) | |
| FCC Coordinate Calculation Program (offsite link to the FCC web site) | |
| FCC
Distance Calculation Program (offsite
link to the FCC web site) The last three calculators above are courtesy of Dale Bickel of the USA Federal Communications Commission. |
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| An old DB Products DOS program that calculates down-tilt for antennas 128kb ZIP file | |
| An old DB Products DOS program that plots some antenna patterns 383kb ZIP file | |
| 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
| Base and mobile antenna cutting chart from Larsen Antennas a 668kb PDF file from the Larsen web site, specifically the Technical Reference page. | |
| Low band radios that cover a wide frequency range (like the GE Delta, GE Rangr, Motorola Syntor X or Syntor X-9000 which covers 28-54 MHz in one range) have a problem: the antenna bandwidth is much narrower than the radio is. Motorola came up with a solution: a "Diplex Antenna Matching" kit that allowed two differently cut low band whip antennas on one radio (i.e. one could be on 36 MHz and the other on 43 MHz), and done in a way that prevented them from interfering with each other. The two antennas can be cut to any two low band frequencies. Here is the documentation on the kit (Motorola manual part number 68-80100W86, a 1.9mb PDF), which contains three pages of info - enough to duplicate it yourself. |
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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.