[Elecraft] 12 meter K3 RFI from nearby FM station

[Fred Jensen]

I easily could have misread the original emailed problem, but he 
included the note that this RFI occurred with all antennas [and I guess 
other cables] disconnected which is very strange indeed.  If that is so, 
then I doubt stubs/filters on the antenna circuits would cure the problem.

His list of frequencies might suggest some sort of intermod between 
constant signals, one being the FM carrier, and possibly their 
harmonics.  Very strange problem at any rate.  FWIW, and Phil can 
correct me, but US FM/TV stations are usually authorized in EIRP, I 
think ... we referred to KSBY-TV, where I worked while in college, as 
"Full-power television for the Central coast, one hundred thousand watts 
on Channel 6 in San Luis Obispo" on ID's.  That was EIRP, 10 KW to a 10 
dB turnstile.  If that's still true, it would seem a 2 KW EIRP FM 
station 2 miles away shouldn't be a big deal.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org

On 2/10/2016 2:04 PM, Ron D'Eau Claire wrote:
> I agree. Even better.
>
> 73, Ron AC7AC
>
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bob
> McGraw K4TAX
> Sent: Wednesday, February 10, 2016 9:18 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] 12 meter K3 RFI from nearby FM station
>
> An electrical 1/4 wavelength of coax as an open stub at the FM frequency,
> connected using a T at the receiver input, will notch the FM TX signal.  It
> won't attenuate other frequencies across the ham bands including 6M.  Plus
> one can transmit with the stub arrangement in place.
>
> 73
> Bob, K4TAX