[Elecraft] KX-1: Broadcast breakthrough on 20m

[Wayne Burdick]

Hi Stephen,

The KX1, like most low-current QRP transceivers, uses an active mixer  
in the front end. IMD products can appear in the mixer's output  
spectra when large signals are present at the input, especially if the  
LO (local oscillator) injection is insufficient.

Try backing down the RF GAIN control on the KX1. If the "breakthrough"  
signals you're referring to decrease in amplitude faster than the  
desired signals, chances are you're hearing IMD. If all signals  
decrease in amplitude at about the same rate, you could have a problem  
with LO injection, or the 20-m band-pass filter may need realignment.  
The KX1's DDS LO has some level of harmonic content, and if the input  
filtering is not sufficient, LO harmonics might mix with very strong  
signals to produce outputs that show up in the ham band.

If you have an oscilloscope I can give you a few test points to look  
at. But you could also try peaking the band pass filter per the KX1  
owner's manual.

73,
Wayne
N6KR


On Oct 27, 2009, at 1:23 PM, Stephen Prior wrote:

> ...I threw about 10m of wire out of the
> hotel window (just to listen) and was surprised to find three or  
> four strong
> broadcast stations around 14.2MHz...