A homebrew 2m FM rig

This rig was homebrewed in the year 1987.

It was inspired by G8FWM - OM Brian L.Phillips' article, 'PW AVON - a 10W 2m FM Transmitter', in Practical Wireless (July - September 1978).

http://www.americanradiohistory.com/Archive-Practical/Wireless/70s/PW-1978-07.pdf
http://www.americanradiohistory.com/Archive-Practical/Wireless/70s/PW-1978-08.pdf
http://www.americanradiohistory.com/Archive-Practical/Wireless/70s/PW-1978-09.pdf

OM Brian's dedication to detail and his 1:1 PCB layouts made it easy to homebrew the coils and the 'island pad' style PCBs.

The transmitter stages are 8 MHz crystal oscillator, reactance modulator and multipliers for 24, 72 and 144 MHz. All stages, from 8MHz crystal oscillator to 144MHz multiplier, use BC109B transistors. Three 2N3866 stages amplify the output to 0.5W. A vintage antenna relay does the T/R switching.

Homebrew 2m FM rig - inside view
The receiver section is a converter, wired on perfboard in 1983.

It is based on G3OGR - OM F.G. Rayer's two articles 'Converter for 144-146MHz' and '144-146 MHz Amplifier', in his book 'Projects in Amateur Radio and Short Wave Listening' (1981).

These articles are also covered in '50 (FET) Field Effect Transistor Projects' by the same author.

http://www.talkingelectronics.com/projects/TheTransistorAmplifier/50FETProjects.pdf

3N200 insulated-gate, dual-gate mosfets are used for the preamplifier, amplifier and mixer stages. A couple of 2N918 transistors for local oscillator and first doubler are followed by a 2N2369 second doubler for 133MHz.

The quick and dirty 12VDC power supply was put together with junk box parts.

An aluminium baking tray served as the enclosure.

Crystals ground for the 2m FM rig
The 12 MHz output of the converter was fed to my RCA BC-312-D Receiver, used as a tunable IF and slope detector.

Vintage 8 MHz crystals were ground by hand to the desired frequencies, using QSOs received on the converter and 'well-warmed' BC-312-D as reference.

The pads for FT-6U crystals and trimmers became redundant on account of non availability of the crystals. An 807 tube socket was found suitable to plug in all configurations of vintage crystals used.

With a ¼ λ Ground Plane Antenna, this rig served me well for both local and DX contacts till I could lay my hands on an ICOM IC-02A in the year 1990.

Related post: Simple ¼ λ Ground Plane for 2m
______________________________

Tests for power on a 2m antenna

Caution! To avoid dangerous RF exposure, these tests are to be carried out using a maximum power of 5W only. A 2m HT is quite safe for the purpose.

The ability of a neon lamp to glow in the presence of an electromagnetic field made it a handy RF indicator of yesteryear. Many a handie talkie (HT) was tested by just holding a NE-2 near its whip antenna.

Curiosity led to a search of the junk box for a NE-2 but a different type, having plate electrodes, was found (see inset).

Power was applied and the antenna probed with the neon lamp. A static-charged plastic bag, placed in between , helped trigger the neon lamp.The ensuing red glow was sustained by the RF energy. The plastic bag may not be required when dry weather and synthetic clothes make it more conducive for the test.
Neon Lamp Test on J-Pole Antenna
At high voltage points the neon continued to glow even when moved away from the antenna.

Neon Lamp Test on Rubber Ducky
A more reliable method is to use a dipole as a pickup and a 6.3V-150mA dial lamp as the indicator.

My version of the pickup has two 21" telescopic whips fixed on a wooden strip, with the dial lamp soldered in between. It's quite convenient to push the telescopics in and fold them for storage.

Dipole-lamp pick-up - folded
With only 3.5W from my HT, and the dipole length adjusted to ½λ, the lamp glowed to more than full brilliance at a good distance from the antenna.

Dipole-lamp test on J-Pole antenna 
______________________________