SB303 Receiver noise.

[Michael Waldrop]

Assuming you are not using the 303 in transceive with an SB-400 or
SB-401 and the 50 ohm resistor is plugged into the rear LMO jack, I
would check the power supply caps on the PS/BFO board. If the receiver
is "original", those caps are quiet old and probably quite leaky.

I had the exact same problem with my SB-303; an S9 noise level without an
antenna connected. This is what I did to fix the problem.

All of the electrolytics on the PS/BFO board were replaced. Next,
I cleaned each board's finger contacts including the RTTY board, all pots
including the 4 blue pots; 15 volt, 3.5 volt bias, meter zero and meter
full scale. Then I performed the voltage and meter adjustments. With the 50
ohm resistor plugged into the rear LMO jack, the volume set to 9 o'clock, RF
gain and Atten pot completely clockwise, I powered up the receiver.
Adjusted the 3.5 and 15 volt settings along with the meter adjustments.
With no antenna connected, the receiver was as quiet as a church mouse and
the meter rested at zero. Using the calibrator, adjusting the PRESELECTOR,
the signal level was at S9. Connecting an antenna, and signals I could not
hear before were loud and clear.

73's
Mike
W5RKL




On Sun, 4 Mar 2007 17:53:10 -0500, Jim Sutherin
<jsutherin at WIRELESSINTRA.NET> wrote:

>I have a sb 303 and a 301, I recall a posting that mentioned how quite the
301 was and they were right. I was wondering if there was any mods or
replacements in the 303 front end that could possibly inprove the recievers
noise level. I always get a rushing noise when a signal is not present.
>
>
>Thanks
>Jim K8DHC
>
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