Hello again, guys. I'll get right down to the facts. I'm having a bit
of trouble neutralizing this amp. With 10 watts input, I can get the thing
"tuned" to show 250+ output, but when I unkey, the plate current will
increase to 350 to almost 400ma. As far as I know, this isn't healthy for
the amp, so I quickly detune the amp to stop it from oscillating. I'm trying
the neutralizing screw, but it really doesn't seem to do much. Is there a
"standard" set of component values to use to stop this from happening at 144
MHz? Also, when the amp seems to be adjusted properly, the FT-857 I'm using
will always show a high SWR - can my input match be affected by the
oscillation? I'll be honest - I haven't tried an SWR meter in line yet, and
since I just lost another diode in the HV, I can't try it tonight to see
what it actually is. Could my whole problem be that I'm using a transmitter
that's "too new" for this amp? This thing's really got me puzzled since I
checked just about all of the components inside this thing and they all
appear to be fine. Well, except for the socket. It was shorted internally,
so I took it apart & (hehehe) taped over the bad spots in the bypass cap. I
am getting another socket, but didn't think this would cause the
oscillation. Is that bypass cap my whole problem since I'm sure the value
isn't what it's supposed to be? I know that tape fix sounds stupid, but I
wanted to try something in the meantime. An experiment. Thanks again.
...Learning in RI (Larry)
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