[Elecraft] K3 receiver desensing on CW during contest

[Jim Brown]

On Wed, 25 Feb 2009 01:50:18 -0700, Bill W5WVO wrote:

>While all these transmitters except 
>Channel 2 have fundamentals well above 54 MHz (I run a DCI bandpass filter to 
>keep it out of my preamp), the accumulated grunge from the transmitters' 
>perfectly legal low-level spurious emissions and passive mixes are enough to 
>render 6 meters unusable for weak-signal work in the direction of the 

Yes. Several decades ago, I was on the tech committee that maintained ham 
repeaters on 2M, 220, and 440. All VHF and UHF broadcasters in Chicago are 
located on two buildings downtown -- Sears and Hancock. Thanks to that grunge, 
a 2M receiver was completely useless anywhere near downtown. I did manage to 
make a 220 MHz receiver in a 101st floor window at Hancock "sort of" work to 
fill in holes caused by shadowing of the main RX. It was shadowed by the 
building from the transmitters for Ch 9 and Ch 11.

I suspect that your 6M problem will be greatly improved when your Ch 2 goes 
away. I had a Ch 2 to deal with in Chicago too, but they were only running 
about 20-30kW ERP. One very large blessing of DTV is that nearly all the low-
band VHF channels are going away (that is, Ch 2-6). The reason is that DTV is 
rather susceptible to impulse noise, and impulse noise is much worse at low 
VHF than at higher frequencies. 

73,

Jim Brown K9YC