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IC-706 "Mark 1" Silent on LSB and USB

Sep 15th 2011, 01:10


Joined: Aug 1st 2011, 09:03
Total Topics: 0
Total Posts: 0

I have an ICOM IC-706 "Mk1" radio that I picked up used and have been using primarily as a 2M base. Now I'm attempting to use the HF capabilities and find that I can not hear anything in LSB or USB modes at all. When I switch my mode over to LSB or USB the radio is silent (even with squelch all the way open).

Beside it on the bench, I have an IC-735 that can pick up. I can swap antennas and the problem sticks with the IC-706. I can Tx from the 706 and hear it on the 735, so transmit seems to work (though I haven't tested it over any sort of range). Tx from the 735 to the 706 do not go through.

If I do open the squelch, the Rx light turns on. If I switch to WFM, I can hear a variety of radio stations through the 7Mhz range. AM mode also seems to work. I have not tested RTTY.

In troubleshooting, I have done a complete reset on the 706. As far as I can tell, there is no "PL Tone" type settingo n the HF side.

My best guess is a bad filter or connection. Looking for any pointers on this issue.
Sep 15th 2011, 12:49


Super Moderator

Joined: Apr 4th 1998, 00:00
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Total Posts: 0

The same filters are typically used for transmit and receive.

I'd suggest listening for the various oscillator signals used on the 706 with the IC-735's general coverage receiver. In particular, there is a beat frequency oscillator used at the last mixer or product detector to convert the received signal down to audio that you should look for.

There is a active Yahoo group for repairing amateur radios

Yes, PL tones are not used on SSB/CW.

Zack Lau W1VT
ARRL Senior Laboratory Engineer

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