Re: Mirage B23A linear amp.
This is indeed biased AB; there's a simple bias-supply using a forward-biased 1N4002 diode and some low-value resistors feeding DC to the MRF240A base: if I force it into transmit-mode in the absence of any actual drive the PA starts drawing around 200mA - there's a "FM/SSB" switch on the front panel but all that does is to add a 'hang' time to the RF sensing changeover in order to avoid the relays trying to follow the average speech-envelope on SSB and chattering themselves to destruction.
[there's a 'SSB Delay' pot accessible through a convenient hole on the side of the case]
Last edited by G6Tanuki; 1st Aug 2021 at 7:20 pm.
|