The All-band HF Amateur Radio Transceiver: Just waiting to be modified
Erhart DF3FY, as well as providing a fix for the audio pop problem, has upgraded his PA output stage with RD16HHF1s. Erhart suggests the IRF 510s are not ideal for portable field operation. The small output transformer represents a mismatch for power outputs greater than 5 W so he has incorporated a new output transformer. He is now achieving 18w output on 20m and 12w on 10m, with an average of 15w output on all bands.
For details see his PDF file: fixes PA.
Erhard Haertel DF3FY comments, “There are a lot of proposals for addressing the RX-TX audio pop with the uBITX, but none of them really works”.
Erhard has come up with his own pop-fix that involves muting the TDA amplifier during TX, turning the IC on with the 12V RX line (to prevent SSB noise in headphones during transmit) and additional decoupling for the 12V line.
Erhard says, “This fix cures all the issues”. Write and tell us if you have tried this fix.