[Elecraft] K3 Overload from WYFR

[Geoffrey Mackenzie-Kennedy]

Hi Lyle,

> You might try adding an attenuator between the K3 IF out and the LP-PAN
> IF in and see if the overloading disappears. If so, it might indicate
> the LP-PAN system is overloading rather than the K3.
>
> 73,
>
> Lyle KK7P
>
> PS - The K3 blocking dynamic range is 20 to 30 dB better than PC-based
> SDRs.  So I suspect you are seeing a weakness in the PC-based SDR system
> rather than the K3, but I've been wrong before! :-)
--------------------------------------------

I'll probably have to eat Humble Pie, but with respect I don't believe that 
Steve has an overload problem, but could have a spurious mixing problem, the 
result being similar to intermodulation. Also, the problem might or might 
not be caused by the K3 nor LP-PAN, which would not be difficult to 
determine if another receiver is available.

The screen capture of WYFR's carrier at 6985 kHz, and a family of products, 
shows that the spacing product to adjacent product is roughly  4.64 kHz  if 
the low level intermediate products are ignored, which they can be in this 
exercise. If these products are the result of mixing (or are IMD products), 
there has to be of course another signal spaced 4.64 kHz from WYFR's 
carrier - and there is one at 6980.36 kHz, whose amplitude fits the 
amplitude pattern of the products.

Of course, the device or transmitter generating this signal at 6980.36 kHz 
might in fact be operating at a sub-harmonic frequency e.g. a MF BC station, 
and the rogue mixer itself is generating the 6980.36 kHz harmonic.

73,
Geoff
GM4ESD