[Elecraft] Re: Transmitted audio distortion on certain frequency

[Wayne Burdick]

Walter Wilson wrote:
> 
> I have a very distorted transmit audio (listening on another receiver)
> around 7.183 KC on LSB.  If I move up or down the band only 4 or 5 KC,
> everything is clear again.  On USB, the problem occurs at 7.180 KC.  Any
> ideas???
> 
> Walter - KK4DF

Hi Walter,

I believe you have an instability condition that occurs when the synthesizer's
reference and VCO dividers are at the same frequency; this occurs only in the
vicinity of 7180-7185 kHz. Try soldering a small capacitor, say 33 to 56 pF,
between pins 12 and 13 or U4 (MC145170) on the RF board. Also make sure that R19
is 2.7 k, not some smaller value, and that RFC15 (at pin 16 of U4) is not
broken. 

If none of this helps, consult Gary (support@elecraft.com) for other ideas. If
it *does* help, re-run CAL PLL to ensure that the now-stable synthesizer tunes linearly.

73,
Wayne
N6KR