The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Hi Guys. Just bought a Superstar 3900(Cobra 148 rip off) and noticed they've done away with the old 2sc1969 final and replaced it with 2 x Irf520 outputs. Anyway, to cut a long story short, i keyed on fm/am and my power meter shows 10 watts which is fine, however when i talked into the mic on ssb i was only peaking 2 - 4 watts which wasn't good. The only way i could achieve 20 watts or so was to whistle loudly into the astatic mic(i tried several mics to same effect). Even talking loudly didn't achieve more than 4 watt pep. On this note, i decided to open the radio and alter Vr12(ssb power/alc) so that i could voice peak upto about 12 watts or so. It still peaks 20watt or so on a whistle. Having done this, do i need to alter/tune anything else or will me altering this variable resistor have upset any workings of the radio - ie bias, etc. Your comments are much appreciated. Regards. Damian.

Adjusting the ALC won't upset anything, it just turns the SSB output up but don't adjust it for Maximum output, turn it down slightly from the maximum power out position.
What ever you do, don't try to adjust the bias setting for more power or you'll blow the outputs on that radio.

Hi Dave. I asked you the same question last night on the rig not realising you were on here! Nice to hear you around still. Damian.

I adjust the ALC while monitoring the output waveform on an oscilloscope. Turning the ALC up too much will result in distortion. Are you useing a PEP watt meter?