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CW Noise upon switching from transmit to receive


My setup is a 6600M + PGXL into a vertical antenna. I run CW mostly with BW set to about 150Hz, AGC set to medium and RF gain set to 0dB. I adjust the agc to just start squelching background noise. Only one slice is operating.

Recently, in contests on 20m I have been experiencing a loud blast of noise that starts when the radio switches from transmit to receive and fades away after 1-2 seconds. The noise sounds exactly like a nearby powerful station overloading the receiver, except it occurs with no stations closer than about 3-5 KHz.

After the 1-2 second recovery period the noise is gone and the receiver performs normally even though the loud nearby stations are still transmitting.

I am not sure but the noise does not seem to appear on the waterfall under my receiving frequency so, it is not a spurious signal generated by some other station. I think it is generated inside the receiver.

It is not intermittent, it occurs on every transmit-to-receive transition but, does not occur when no other stations are on the band.

Is there some setup that I can change to eliminate this problem?


Jim Charlton AD0AB



  • bahillen
    bahillen Member ✭✭✭

    Did you set TX delay to 10-20 ms?

    Radio Tab - TX - TX Delay




  • Hi Bill,

    Yes, the TX Delay is set for 25.

    It really seems like as soon as the radio switches to receive, the front end is momentarily overloaded and some sort of internal agc reduces the gain over a period of 1-2 seconds. After that brief recovery period, the noise is gone and the receiver rejects adjacent signals, even really strong ones.


    James Charlton

  • K0FLY
    K0FLY Member ✭✭✭

    I can remember something like you are hearing. Just for grins set your CW filter to "LOW LATENCY" and turn off "AUTO". I have no idea if that will work, it solved my problem.

    Gayle K0FLY

  • Gayle,

    Thanks, I'll try that.


    Jim AD0AB

  • Gayle,

    Sorry to take so long to reply, but your fix seems to have worked. I just finished a CWops sprint with a lot of closely spaced sprong signals and not a sign of the noise.

    Thanks for the advice,

    Jim AD0AB

  • K0FLY
    K0FLY Member ✭✭✭

    Glad it worked for you. Thanks for the feed back

    Gayle K0FLY

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