This project has its origins in the wartime 17 set which was a simple phone AM TCVR for use on about 50 MHz. The receiver here is a regen TRF with stages for RF amp, tuning/detector, regen, audio pre-amp followed by the AFG pot and audio output; the latter can drive a loud speaker or phones. The RX tuning parts use toroids, fixed capacitors and trimmers with the PolyVaricon tuning control for any of the traditional harmonically related bands. The phone transmitter is crystal controlled with a nominal carrier level of 1.5W on 12 volt supplies; it uses amplitude modulation of the TX supply voltage via a small transformer driven by an audio power amp (of the same type as used in the RX). There is a speech amplifier stage for the common CB type dynamic mics, and preset for the mic gain control. The RF output includes double half wave filters with a TR relay controlled from the PTT switch. The transmitter frequency is obtained by multiplying up and filtering (when needed for the wanted band) from a harmonic of the crystal frequency that is present in the digital oscillator. This approach is the easiest way to get to 6m (or lower) when combined with a high speed MOSFET in the output stage. If true VFO operation is required for the TX, then an external VFO must be used. Crystal frequencies are available that will get the TX into the appropriate parts of all the main bands - please ask for details if you need them. The kit includes a blank single sided PCB for your own front panel. The main PCB is double sided 100 x 160 mm, and the supply range is 9 to 22 volts. The photo shows a 6m version. Price is £59.
This is a small superhet phone TCVR for any single band 20 to 160m. Its small size will appeal to those wanting a phone rig for /P operation. Though NOT electrically very complex, the 100 mm square main PCB is very full - hence in this category! Many extras can be added - digital readout, speech processor, Audio Extras kit, and the 10 Watt Linear Amp. On the lower bands, the VFO frequency alters with each band and coverage is divided into 3 sub-bands for a low tuning rate on the variable capacitor. Higher bands are possible with the Mixer kit. It is a bi-directional superhet with an IF amp that is used on receive and transmit; the 6 MHz 5 crystal ladder IF filter is followed by a conventional detector and audio stages. Minimum supply is 8 volts but on 13.8v the TX produces 1.5 Watts. Low pass filters are included. Suits low Z microphones. It is supplied with all parts for open construction. Price £79
Photo of the Fivehead with the 10W Linear attached at the rear:-
I regret to say that I have decided to temporally postpone work on this project as it had become too complex and costly for today's financial climate. The target of a multi-band phone TCVR is still one of my projects but it requires a rethink! Meanwhile the two audio kits that were developed for the Minster (Notch filter and Audio Extras) are available - see Accessories page.
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