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Maintained by Robert Meister WA1MIK
Contributions are ALWAYS welcome.

There are other good articles on the Technical Info page

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

Test Equipment or Parts Thereof:

Build an Isolated Tee Sampler for a Bird 43 Wattmeter   By Kevin Custer W3KKC
Build an IsoTee Sampler for the Bird from a blank slug!
Build your own Iso-Tee   By Ted Bleiman K9MDM
Build an Iso-Tee from an ordinary T-adapter.
A Photo Tour of a Bird Wattmeter Element   By Robert W. Meister WA1MIK
Ever wonder what's inside one of those elements? Read on.
A Poor Ham's Deviation Meter   by Robert W. Meister WA1MIK
A theory and practice article on measuring deviation of FM transmitters.
Build Youself a Service Monitor? Well, sort of   By Tom Alldread VA7TA
A simple deviation monitor circuit used with a scanner receiver.
A purpose-built Motrac Metering set   By Robert W. Meister WA1MIK
I needed to tune a Motrac-based Compa-station but had no official metering set. I had a meter; I bought everything else. You can modify the design to suit your needs.

RF: Amplifiers, Antennas, Duplexers/Filters, Preamps:

Additional Construction Project info can be found on the Antenna Systems page.

Multi-Element Exposed Dipole for 2 Meters   By W2EWY & WB2ICP
A good exposed Four-Bay Dipole Array construction project.
Retuning a Stationmaster type antenna   By Jim Barbour WD8CHL
Omni-Gain Collinear Repeater Antenna Construction Project   By Mike Collis WA6SVT
A great 144 to 1300 MHz antenna project - and there are followup articles on the Antenna Systems page at this web site.
Build a Rugged Half-Wave Coaxial Antenna   Coaxial sleeve dipole antenna (offsite link)
Duplexer coupling loops and how they affect performance   By Kevin Custer W3KKC
An analysis of factory-built vs home-built loops.
Someone say "6 meter duplexer"?   By Jeff DePolo WN3A
A comprehensive conversion of a lowband pass cavity to band-pass band-reject.
Heliax 6 Meter Filter construction article   By Robert W. Meister WA1MIK
A comprehensive filter construction article using 1-5/8 inch hardline.
Build a set of CATV Hardline Matching Stubs   By Kevin Custer W3KKC
Build a Band Pass-Band Reject Two Meter Duplexer   From the W1GAN article in the July 1972 QST
Build a good quality GaAs FET Preamp   By Kevin Custer W3KKC
For 2 meters, 220 and 440.
Combining a VHF voice repeater and a digipeater   500 kB PDF file by Eric Grabowski KH6CQ
Share one antenna and feedline by adding some filtering and a combiner.
Converting the Henry Radio C100D10R to C100D30R   by Robert Meister WA1MIK
A quick mod allows the amplifier to work with 30 watts input power rather than 5-10 watts.

Audio: Amplifiers, Filters, Limiters:

Build an audio buffer amplifier   By Kevin Custer W3KKC
Kick the audio in the butt.
A simple audio mute circuit   20 kB PDF file
If you're using discriminator audio and need to mute it, this circuit will do the job.
A squelch-controlled audio amplifier   15 kB PDF file
This combines the functionality of the LM386 amplifier and a mute circuit. Originally designed for the GE Phoenix radios. It used unmuted audio from the top of the volume control, and a COS signal that goes high to unmute the amplifier.
PL-CG (CTCSS) Filter Construction Projects   Build several PL (CTCSS) Filters!
Audio Buffer and De-Emphasis circuit   By Lou Harris N1UEC (offsite link)
Use this circuit after a repeater receiver to de-emphasize the audio going to your controller.
Pre- and De-Emphasis circuit component values   By Oliver Buland W9ZGS
Pre-calculated common component values.
An Audio Equalizer for Communications Use   234 kB PDF file by Robin Rumbolt WA4TEM
A five-band audio equalizer.
Audio Limiter for NBFM   By Kevin Custer W3KKC
A hard audio limiter like you'd use for broadcast audio.

Power Supplies and Modifications:

A 13.8v 40a switching power supply   1.2 MB PDF file by Manfred Mornhinweg XQ2FOD
This switcher is RF-quiet from 50 kHz to over 40 MHz and is over 85% efficient.
The Daiwa PS-304 power supply gets Anderson PowerPole Connectors   By Kyle Yoksh KØKN
A step-by-step procedure that increases the usability of a good power supply.
Use an Astron power supply remotely?   Look here!   Don't run to the repeater site to reset that Astron anymore! (scroll down to the Reset Circuits)

Repeater Controllers and Interfaces:

StarTech CM108 based USB sound adapter conversion article   By Kevin Custer W3KKC
This is for AllStar (Asterisk) VoIP.
Generic CM108 based USB sound adapter conversion article   Author unknown - likely Steve RoDgers WA6ZFT (offsite link)
This is for AllStar (Asterisk) VoIP. A local copy can be found here.
Basic Stamp 1 and 2 Repeater Controller construction projects   By Roger Cameron NØYOX
Inexpensive repeater controllers using the Basic Stamp.
Other Repeater Controller Construction Projects   Build Controllers and stuff for them!
Build a Two Channel Signal to Noise Voter   From the WB2WHC article in October 1992 QST.
A simple Echolink interface   By Matt Krick K3MK
Easily constructed with about $10 in parts from Radio Shack. Should work with any radio.
A VHF/UHF/LINK repeater interface/controller   239 kB PDF file
This is a set of nearly identical schematics for circuitry used to provide cross-band inter-agency communications.
The C.A.R.S. Repeater Controller   1.5 MB PDF file. Scanned by Chuck Kelsey WB2EDV. Cleaned up by Bob WA1MIK.
This is the scanned documentation for the Crawford (PA) Amateur Radio Society repeater controller, circa 1987. Probably not available any more.
RPT81 Repeater Controller by W8SBD   685 kB PDF file. Scanned by Eric K8OHZ, cleaned up by Bob WA1MIK.
This was a full-featured repeater controller circa 1996. Probably not available any more.

Useful, Small, and Handy Repeater Circuits:

The Repeater Builder's Friend   By Matt Krick K3MK
A device to help to you fix your repeater or program your controller.
Build a telephone line filter that doubles as a lightning protector   By Kevin CusterW3KKC
A phone line filter and protector.
A Phone Line Busy Sensing Circuit   By Monte Smith, WDØDIR (from ACC Notes, April, 1986)
If you need to share a phone line between your home and a repeater, here's how.
A Push To Talk Delay Circuit   By Kevin Custer W3KKC
For ACC controller users.
A COR Hang Timer Circuit   By Kevin Custer W3KKC
A simple controller of sorts.
Build a simple COS detector circuit   By Kevin Custer W3KKC
For creating a COS signal on radios that don't have one.
Analog noise squelch   By Kevin Custer W3KKC
A quality COS logic interface with a professional printed circuit board.
Analog noise squelch and CTCSS decoder   By Kevin Custer W3KKC
A quality COS and CTCSS (PL) logic interface with professional printed circuit board.
The Jet Propulsion Labratories "Smart VOX"   By Randy Hammock KC6HUR and Jan Tarsala WB6VRN
A Crystal Heater construction project   By Bob Dengler NO6B
Make that crystal stable.
CH-25 Crystal Heater Kit   By Kevin Custer W3KKC
As above with professional circuit board.
A Tone Beep Keyer for Repeaters   98 kB PDF file by Art Gentry W6MEP (Reprinted from May 1974 QST)
Obtain an Audible Indication of Off-Frequency Operation.

Fan Controllers for Radios and Repeaters:

A Simple Repeater Fan Controller   18 kB PDF file by Robert Shepard KA9FLX
A Repeater Fan Controller using a 556 IC   17 kB PDF file by George Henry KA3HSW
This is a follow-up to the above with a modification to use a single 556 chip.
A Current-Sensing Fan Controller   by Willie Barnett N1NKM
This circuit is installed inside a linear power supply and adjusts the fan speed based on the current that's being drawn by the radio, so the fan runs faster when the radio is transmitting. Several alternate (and untested) designs are also provided.
A Temperature-Controlled Radio Cooling Fan   by John Haserick W1GPO
John used a commercially available temperature controller / thermostat to operate a fan under his 6-meter radio.

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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.