I just put up an antenna for 20M so I can check into the nets and also
chase a
little DX. As Murphy is alive and well, the 20M band had all kinds of
noise/ pulses/FMing with a S7 to S9 noise level. BTW today its normal.
And my Triton IV that I had been only listening with decided to attenuate
the receive signals after a
few transmissions. After sitting awhile, it was normal again. Until
transmitting.
I have a signal generator, and a scope, but wanted to do a quick and easy
problem isolation. The Cal was attenuated too so I knew the problem was
following the
front end of the receiver. My technique was to heat circuitry with a hot
air gun from
Harbor Freight and see if I could duplicate the intermittent failure. Sure
enough the
AGC-IF board was the problem. I could heat Q6 and the receive signal would
drop. Spraying a little bit of Cool Spray on the transistor cooled it down
and the
radio worked normally. I replaced the MPS6514 with a 2N2222A and all is
well.
Alternating heat and cold is a good way to find temperature sensitive
intermittent problems. Maybe this will help with other troubleshooting
problems. BTW I love these discrete components.
Wes
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