W5OT@aol.com wrote:
> My rag chew buddies report that I have a low level hum or noise (about 30 db
> down) on my audio when transmitting LSB. Previously, I had used the rig for
> CW so didn't know about the problem.
>
> It seems to be some coupling inside the cabinet, since disconnecting the mike
> and keying the transmit in LSB produces the noise as well as when the mike is
> connected.
>
> Any experience with this?
>
> tnx es 73 de John, WA5TWL
>
>
John,
You may have some carrier on your LSB signal. I had this happen, and Don at
Ten-Tec said that it seemed to happen more on LSB than on USB. The adjustment
controls for LSB are R3 and R4 on the TX Audio board, at the left rear of the
top
of the chassis. You have to remove the bracket with the speaker to get at them.
I have a Heath SB-610 monitor scope, and I simply turned the pots until I
minimized the width of the scope trace line with no audio out. The adjustment
was not supercritical. You might even be able to do this by setting an output
wattmeter to a highly sensitive setting and minimizing the output with no audio.
I think I turned on the linear amplifier and tuned up to 500 watts out into a
dummy load, then put it in LSB and closed the ptt. The carrier was real easy to
see then, and I adjusted for minimum.
73,
Jan, KX2A
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