XPost: uk.radio.amateur, free.uk.amateur-radio, rec.radio.amateur.equipment XPost: rec.radio.info
SADARS
///////////////////////////////////////////
17 Feb 2022 - A 400 Watt 80M AM transceiver by Graham G4JBD
Posted: 18 Feb 2022 04:12 AM PST
https://sadars.co.uk/wp/archives/3040
Grahams transceiver
A boat anchor it is NOT! This high quality transceiver for 80M runs a cool 400w in Class E and is small and light at only 3kg, including the power supply! The original design was by Dave GW4GTE and the PCBs and parts were from Eric GW8LJJ. (www.s9plus.com)
Graham explained the amps Switch-mode has many advantages, it is
theoretically 100% efficient. The audio processing uses a well tailored RMS
AGC which controls maximum modulation without the usual heavy modulation transformer. Syllabic compression tracks the users voice power. A very
sharp, easily tailored low pass filter keeps the signal bandwidth very well controlled resulting in excellent on air audio reports.
Graham went through each stage of the transceiver to explain how each stage operated to produce the phase width modulated signals with 100% modulation.
The receiver part of the unit is single conversion superhet allowing a
choice of 80m or 160m during construction. No special tools were required during construction but Graham did admit to purchasing an illuminated free standing magnifier (£23). He did, however, use his oscilloscope to set the
PWM and drain waveforms. His shack receivers display was used for
monitoring modulation bandwidth. A most impressive part of this build was
the cost, only £347 total.
So, what to add next? CW keying and a BFO, and perhaps add a 160m matching network.
Graham felt it would make a fine addition to the GB2RS news in AM for 80m. Graham (L) keys xmtr while Dave (centre) measures signal
--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)