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Maintained by Robert Meister WA1MIK
Contributions are ALWAYS welcome

There are other good articles on the Construction Projects page.

This page has recently been reorganized.
Everything is still here; items just got grouped together by function.

Repeater-Related Information:

Repeater Application notes and Articles   offsite link to Chip Angle's web site
Look for the "Repeater applications notes" - proven repeater system design techniques from a VHF / UHF / weak signal / contesting fan and RF design guru
While it's not worth a separate article, you don't want to have a UHF repeater input between 446.0 and 446.100. The European FRS radios (the service is called "PMR 446") uses 8 narrowband channels in that range (complete with user-selectable CTCSS codes), specifically: (1) 446.00625, (2) 446.01875, (3) 446.03125, (4) 446.04375, (5) 446.05625, (6) 446.06875, (7) 446.08125, (8) 446.09375 ... sounds like a good area for digital / Dstar / P25 repeater outputs or point-to-point packet links.
Monolithic Crystal Filter Application in Amateur VHF Repeaters   by Joseph M. Hood K2YAH   208 kB PDF
Mr. Hood describes how a crystal filter can be placed in front of a VHF repeater receiver to reduce desense and intermod, then uses a preamp to make up for the loss. He forgets that once your 5 dB of insertion insertion loss attenuates a barely understandable signal down to a noisy signal that any amplification after it just amplifies the noisy signal. Personally, I'd put a high-third-order-intercept preamp (like an AngleLinear) in front of the crystal filter.
Some thoughts on low band (6m and 10m) repeaters   By Mike Morris WA6ILQ
How about 1200 MHz? Any thoughts on this?   A reply by Jeff DePolo WN3A.
1200 MHz / 23 cm repeaters in the U.K.  An article by Andy G8VLL.
Terminology used around repeaters
An ongoing glossary updated regularly. Contributions welcome.
Why should you really spend $50 to re-crystal a channel element or ICOM?   by Kevin Custer W3KKC, Eric Lemmon WB6FLY, Jeff DePolo WN3A, Robert Meister WA1MIK and Mike MorrisWA6ILQ
Temperature-Compensated Xtal Oscillator (TCXO) tutorial   By Vectron, a company known for precision crystal oscillators. This is good reading along with the above article. 228 kB PDF file.
Crystal Technology Design Guidelines   By Motorola. This is very technical info they send to crystal manufacturers. 2.4 MB PDF file.
Amateur FM and Repeaters from QST magazine 1969   513 kB PDF By Les Cobb W6TEE
This article is an overview of Amateur FM and repeaters and despite the date, the ARRL didn't "get" repeaters and remote bases until about 10-15 years later (Wayne Green and 73 magazine were the driving force as he ran a slew of FM and repeater articles in the late 1960s and all of the 1970s).
FM Standards Article from Ham Radio magazine 1970   5.6 MB PDF By Les Cobb W6TEE
This article is a technical analysis of the wideband (+/- 15 kHz) and narrowband (+/- 5 kHz) modulation standards. With the conversion from narrowband to even lesser deviation standards it's worth reading to understand the history and to see where things have come from.
The Remote Base - An Alternative to Repeaters... from Ham Radio magazine 1977   2.2 MB PDF By Gordon Schlesinger WA6LBV, and William F. Kelsey WA6FVC
Recommended reading for those wishing to relieve congestion on the vhf bands - a definitive description of the difference between remote-base stations and repeater stations.
Two Meter FM repeater separation - 20 kHz Yes, 15 kHz No... from Ham Radio magazine 1985   627 kB PDF By Chris Kelly WD5IBS and Virgil Leenerts WØINK
5 kHz deviation with a 3 kHz audio cutoff creates a signal at least 13 kHz wide (and with 4 kHz cutoff it goes out to 16 kHz), counting only the first set of sidebands. That's why many states went from 15 kHz to a 20 kHz channel bandplan on 2m. This article gives the theoretical information and proves the point (through actual VHF FM receiver selectivity measurements - don't believe the manufaturers specs) that you have more usable repeater pairs using 20 kHz spacing than with 15 kHz spacing.
How much PL Deviation should I run?   by Kevin K. Custer W3KKC
Eliminating the long squelch noise bursts when using CTCSS (PL / CG)   The use of "AND Gating" of the logic signals, by Kevin K. Custer W3KKC
Two-way Radio CTCSS and DCS Codes   This started as the standard list of Motorola PL and DPL codes extraced from an RSS Help file but it has been expanded to include lists from Icom, Kenwood, and Yaesu. Compiled by Robert W. Meister WA1MIK.
CTCSS Frequency vs Decode Time   The myth is that lower PL frequencies take longer to decode than higher ones, and it was probably true a long time ago. This article shows the results of tests made with several microprocessor-controlled radios as well as one that still uses mechanical reeds. The results were surprising, and the answer is: it depends. By Robert W. Meister WA1MIK
CTCSS Doesn't Fix Anything!   Why PL, CG or CTCSS is NOT a cure for interference.   By Mike Morris WA6ILQ
A Historical and Technical Overview of Tone Squelch Systems   A primer on tone systems, with a little on digital systems.   By Mike Morris WA6ILQ
A Chart of CTCSS Tone Numbers   Tone numbers are useless!   By Mike Morris WA6ILQ
How do I link two or more systems together?   by Kevin K. Custer W3KKC and Michael R. Morris WA6ILQ
How can I remote a phone line to my repeater site?   by Kevin K. Custer W3KKC
Programming your repeater controller without a radio or a phone line   by Mike Morris WA6ILQ
While oriented towards an Scom controller the article has enough information that you could use the techniques and circuits to program ANY brand of controller.
Repeater Courtesy Beeps   by Mike Morris WA6ILQ
Sample tone info plus telephone call progress tone specs
How do receiver voting receivers and voting comparators work?   by Mike Morris WA6ILQ
or, what is a voter? An overview of receiver voting systems
How does a Voter and Remote Receiver work?   by Duane Hall and Kevin Custer W3KKC
Some Thoughts on Solar Power and Other Off-The-Grid Repeaters   by Mike Morris WA6ILQ
Some ideas on what to do when there's no power line...
Adding a Separate Control Receiver to a System That Doesn't Have a Spare Controller Port   By Mike Morris WA6ILQ
Weather radios, SAME decoders, and amateur repeaters   by Mike Morris WA6ILQ
Yes, you can have a weather alert or warning receiver activate your repeater - as long as you stay within the rules...
A Phone Line Busy Sensing Circuit   By Monte Smith, WDØDIR, from ACC Notes, April, 1986
DTMF / TouchTone / Touch-Tone Signaling Primer   By Mike Morris WA6ILQ
A very interesting Pacific Bell press release from 1990 that a number of California repeater and remote base operators have used to force Pacific Bell to grant residential phone rates to mountaintop radio sites. The arguments made are simple and compelling and might work anywhere. Well worth reading! (the monthly rate certainly has changed!)
Why every ham owes Art Gentry W6MEP a debt of thanks   390 kB PDF file
The story of how one man started a repeater revolution.   By Bill Pasternak WA6ITF (From QST March 2004)
Hoist a beer and toast Art each May 10th. If you own or use a repeater you owe him...
A collection of repeater-oriented articles by Peter Policani, K7PP
These arrticles were published on his own site that has since left the web. Peter graciously gave Repeater-Builder permission to host certain articles here.
P25 Training Guide   514 kB PDF file
Written by Daniels Electronics, Ltd. This 100+ page file discusses and explains just about everything you'd ever need to know about P25 digital radio systems based on IMBE (Improved Multi-Band Excitation).
Some notes on Simulcasting   by Richard Cohen K6DBR and Steve Bosshard NU5D

FCC-Related Information:

USA Spectrum Allocation Chart   95 kB PDF file
The official chart straight from the US National Telecommunications and Information Administration (NTIA) Office of Spectrum Management (OSM)
Alternate source - from the NTIA server: http// (off-site link)
How to look up an FCC ID number   Sometimes being able to determine who made that device is sometimes very useful... (offsite link - to the FCC server)
How to look up towers   Search all of the FCC registered towers - broadcast, cellular, everything... (offsite link - to the FCC server)
Tower lookup page at the FCC web site   (offsite link - to the FCC server)
VHF Marine channel application and frequency table
    USA Use   (Offsite link to the US Coast Guard Navigation Center web page)
    USA FCC marine channel list   (Offsite link to the USA Federal Commmunications web page listing the VHF marine channels)
    International Use   20.5 kB PDF
While marine channels are not amateur repeater oriented having a little knowledge of the marine channels is useful so that you know where your spurs are and what they are landing on...
And these frequencies are sometimes used for something else, especially away from waterways - for example 156.075 is a marine frequency but it's also "CALCORD - California On-Scene Emergency Coordination - to be used in mobile and portable units at the scene of any emergency incident requiring coordinated action by more than one agency. Yes, it is also Coast Guard channel 61A, but (the state) licensed it out of the old Highway Maintenance pool long before VHF marine was popular (early 1960s). No base stations are allowed (FCC regulation)."
The FCC Class of Station Code list 35 kB PDF
Ever wonder what an FB2J, or an FB4, or an FB6L is? This is a local copy of the one at the Percon Corporation web site.
Understanding the FCC Transmitter Emission Codes
Ever wonder what 20K0F3E means, and how it was invented? This is a "Rosetta Stone" article.
FCC Transmitter Emission Codes   52 kB PDF
A full explanation of the each position of the seven-character emission code.
A list of the USA Television Channels   3 kB PDF ...from back in the days when there were 83 channels and 800 MHz was TV...
Television stations once had Channels 2 to 83, except for 37, which is reserved for radio astronomy. Channels 70 to 83 disappeared in the 1980s and have been reassigned to other uses. Stations gave up Channels 52 to 69 in 2009 as part of the transition to digital broadcasts, and much of that has already been reassigned. As of 2-2012 channels 31 to 51, excluding 37, could be reallocated.

RF-Related Information:

How do I measure sensitivity on this FM receiver?   Measuring receiver sensitivity by Jeff DePolo WN3A.
Measuring Sensitivity - SINAD vs Quieting   There are two standard ways to measure sensitivity, and this article compares them, complete with clickable audio files. By Robert W. Meister WA1MIK
Measuring Receiver Effective Sensitivity   Repeater receiver sensitivity on the workbench is irrelevant - all that really counts is how well it works at the repeater site... by Chris Boone, WB5ITT
Speaking of Preamps...   An interesting discussion thread about 900 MHz preamps extracted from the AR902MHz Yahoo! Group. The information presented herein is applicable to other bands as well.
Fundamentals of RF and Microwave Noise Figure Measurements - Application Note 57-1   712 kB PDF by Agilent Technologies (the old HP Instrument Division)
10 Hints for Making Successful Noise Figure Measurements - Application Note 57-3   967 kB PDF by Agilent Technologies (the old HP Instrument Division)
Practical Noise-Figure Measurement and Analysis for Low-Noise Amplifier Designs - Application Note 1354   1.7 MB PDF by Agilent Technologies (the old HP Instrument Division)
Richard J. Mohr writes about Receiver Noise Figures   458 kB PDF
Resolving high-band paging transmitter interference   by Bryan Dorbert N3ST
900 MHz Frequencies to Avoid When You Set Up Your New Repeater   There's a lot of grunge on 900 MHz and amateur radio is secondary there, and we just have to avoid it. Here's a list of channels to avoid, plus some important information that restricts amateur use in some areas of the United States...
How to install RF modules and transistors   A step-by-step procedure from the experts   by RF Parts company
But it's only a couple of dB!   by Mike Morris WA6ILQ
Feed line (and connector) losses really DO add up!
dB to voltage conversion table (both 50 ohm and 75 ohm)   by Mike Morris WA6ILQ
Decibel (dB) Tables (Common Ratios)   97 kB PDF file
Return Loss (dB) vs VSWR Table   30 kB PDF file
Building Your Own CATV Hardline Matching Transformers   By Kevin Custer W3KKC
75 ohm TV hardline is cheap and here's how to match it to a 50 ohm system
CANUSA Heat Shrinkable Tubing   By Kevin Custer W3KKC
Great for sealing antenna and coax joints
Phase Noise Measurement Using the Phase Lock Technique   330 kB PDF file
AppNote 1639 by Freescale Semiconductor, Inc.

AC and DC Power-Related Information:

AC Power Information - Safety Issues when dealing with commercial AC power   by Mike Morris WA6ILQ
NEMA Non-Locking plugs and receptacles configuration   480 kB PDF; published by Qualtek
NEMA Locking plugs and receptacles configuration   590 kB PDF; published by Qualtek
Capacitors Age and Capacitors Have an End of Life   From Emerson Corp.   405 kB PDF donated by Mike Morris WA6ILQ
This writeup is oriented towards Uninterruptible Power Systems - the battery charger and inverter systems that back up hospitals, etc. UPS systems use large capacitor banks. Our repeater power supplies also use large capaciitors in the DC power supplies. This white paper discusses large DC aluminum electrolytic and AC polymeric film capacitors for use in a UPS application: specifically field aging, failure modes, expected service life and preventative maintenance.
Power Supply Technical Guide   4.57 MB PDF file
Written by XPPower, this 150 page file covers power supplies, UPSes, and other AC and DC power-related topics.

Audio-Related Information:

An explanation of Audio Processing   A reply by Jeff DePolo WN3A.
Flat Audio, and Pre- and De-Emphasis explained   By Morris, DePolo, Schmid, and Custer.
Pre- and De-Emphasis, Explanation and Assistance: Running the Numbers   By Matt Lechliter W6KGB
More on why Pre-emphasis and De-emphasis, with examples on the Motorola MICOR   By Paul Sexauer K3VIX
Explanation of "Flat Audio"   300 kB PDF file By Jeffrey "Shorty" Stouffer K6JSI
He describes how FM two-way radio works, why we have pre- and de-emphasis, then he gets into repeaters and when and why to use flat audio. Resurrected from 2004.

Reference and Miscellaneous Information:

ChipDir   The Master Chip Lookup Web Site (offsite link to a Dutch server)
A Comparison Table of Capacitance Values   by Mike Morris WA6ILQ
A catalog of GE miniature and sealed beam lamps   12.4 MB PDF
Info on pilot lights, round and rectangular sealed beam headlights, PAR series lights, Festoon lights, neon lights, electronic discharge fluroescent lamps, and more.
Poor Man's Spectrum Analyzer   Spectrum Analyzer Kit by Science Workshop (offsite link)
Modulation Spectrums   By Robert W. Meister WA1MIK
How audio frequency, filtering, and deviation affect your transmitted FM signal, how to prevent excessive deviation and splatter, shown with dozens of spectrum analyzer traces.
A very good primer on basic, single-supply, op-amp circuits   160 kB PDF file
A Texas Instruments Application Note (number SLOA058 dated November 2000).
Op-Amp Design Reference   2 MB PDF file
Another Texas Instruments Application Note (number SLOD006B, dated August 2002). This one has a lot more technical detail info than the primer above.
Allied Electronics Data Handbook, 2nd edition (1958)   6.7 MB PDF file
A classic electronics reference, about 64 pages. Chock-full of old component and wiring color codes, formulas, conversion tables, coil winding nomographs, tube substitution data, etc.
Allied Electronics Data Handbook, 4th edition (1964)   3.8 MB PDF file
Newer version of the above reference, about 88 pages. This one includes transistor circuits. Sold for a whopping fifty cents when new. Very nice scan.
Allied Electronics Data Handbook, 5th edition (1969)   4.5 MB PDF file
Yet another edition of this classic electronics reference, 112 pages. Chock-full of all sorts of useful information from the vacuum tube era.
MIL Handbook 413   12 MB PDF file
Design handbook for high frequency radio communications systems. Has info on just about every modulation system known to man, as well as antenna systems, transmission lines, ground systems, modems, etc.
FAA Advisory Circular 20-136B: Aircraft Electrical and Electronic System Lightning Protection   125 kB PDF file
FAA Standard 019e: Lightning and Surge Protection, Grounding, Bonding and Shielding Requirements for Facilities and Electronic Equipment   1 MB PDF file
Grounding in Central Office and Remote Electronic Equipment Environments   5.4 MB PDF file
A CenturyLink Technical Publication.
The application of relay coil suppression with DC relays   33 kB PDF file
An application note from the back of a Leach Relays catalog.
Glossary of Tone Signaling terms   300 kB PDF file
As used with Tone Signaling, Data Signaling, Remote Control, Voice Scrambling, Radiotelephone Interconnect. From Midian Electronics.

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This web page created 20-Aug-2004

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.