On Thu, 05 Apr 2007 23:00:20 +0200, Giulia
wrote in
:

Telspam 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


Ignore Brian (Telspam) -- he'll tell you that your ground plane needs
to be nine square feet.

Refer to your schematic and use your scope to trace the oscillation
backwards through the audio chain starting at the audio power amp.
You'll find the problem stage eventually. Don't forget to carefully
inspect the board for bad solder joints and loose pads.