On Apr 5, 4:00 pm, Giulia wrote:
Telstar Electronics ha scritto:

On Apr 5, 12:57 pm, Giulia wrote:

Hi ,
i have a problem with a president jackson cb ,
in tx there is about 100hz noise (i tx with car battery no PSU),
the noise there is even if carrier is unmodulted (fm and am mode)....
Can someone halp me ?
Schemtics are aviable and i can use an oscilloscope.........

Giulia

Sounds like audio oscillation. What mic are you using? What happens if
you key the transmitter with no mic? Problem still there?

i put an612 pin to ground ......so mic is cutted out .....or carrier
oscillator or power control loop from tx power transistors.......

Giulia

OK... you have pin2 grounded for no input signal. Now use your scope
and trace backward from the RF output collector... moving back through
the audio chain... noting the origin of the 100Hz oscillation.
Normally those radios have only a single transistor buffer for the
mic... followed by a high power op amp (usually mounted to chassis
wrapper) for the audio. Your signal tracing should take long at all.
Hope that helps.

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