rob,
low beta means lower gain, if you swap a high beta for a low beta transistor you would have low idle current unless you turned the bias pot up,
the 477 datasheet specs 40ma idle current, the old rig manuals used 100ma which is what i use as it works well, never tried it @ 50ma or lower in 477 final rigs, i use 50ma for the driver on all uniden exports,
we don't pull the jackson limiter here, we stick a 575 teardrop on
rob,
low beta means lower gain, if you swap a high beta for a low beta transistor you would have low idle current unless you turned the bias pot up,
the 477 datasheet specs 40ma idle current, the old rig manuals used 100ma which is what i use as it works well, never tried it @ 50ma or lower in 477 final rigs, i use 50ma for the driver on all uniden exports,
we don't pull the jackson limiter here, we stick a 575 teardrop on
I tried the radio with and w/o the limiter. When I bought it, it came with the limiter already pulled out. So I put in a new one. Then I took it out and added a 1.5k ohm resistor to the collector and put it back in. That works far better on AM w/o affecting SSB. I can get +100% modulation now (checked on a scope), and set the radio's mod meter to correspond to that. Set the dk to 7w for AM/FM. PEP on AM is just below 20w; that is the best I can get out of it short of pulling the limiter out again. Used a real peak reading meter; not a Dosy.
Not big on using AM, as I use SSB 95% of the time anyway. Use a Astatic Silver Eagle; gets really xlnt reports on SSB all the time. However, I'd like to improve the AM performance if I could.
Is it possible to put an electrolytic cap on the audio chip in order to get some negative peak compression on AM TX? I want to turn up the modulation/squeeze some more positive peak modulation % out of it. Is that possible? Where would the negative leg of the cap go to? Which pin on the IC for the '+'/cap recommendation? Pin 5? Yes; I am trying to draw a parallel to the Cobra 2000GTL board & the NPC mod. The difference is the Jacko doesn't have a AM Regulator like the 2000 does.
Pic:
SuperStar JA and a Blue Dot MRF477