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Re: [RFI] AM Radio Interference On 75 meters

To: rfi@contesting.com
Subject: Re: [RFI] AM Radio Interference On 75 meters
From: K8TB <k8tb@bosscher.org>
Reply-to: k8tb@bosscher.org
Date: Tue, 18 Sep 2012 16:00:19 -0400
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
I don't think it is KFBK. My guess is KCTC, on 1320 KHz. 3rd harmonic is 3960, and even cooler, KCTC operates from 2 different sites. The night site is 5 kw and is located by Antelope North and Antelope, the towers show an address of 7909 Antelope N Rd.

If, the stations is producing a 3 rd harmonic outside of specs, they do have to reduce it. But, it only has to be down to a certain level. I measured one Am on 1300, omni mode, in its driveway, and you just barely hear the 3rd on a good communications receiver. But 3 miles away, the 3rd was S7. Ham neighbors aluminum downspout.

First thing to do is to get a step attenuator in series with the receiver. Drop the signal by 10 db, and see if the S meter goes down by 10 db. If it does, the 3rd is outside his rx. Could be the 1320 signal, could be developed someplace else. If you add 10 db or 20 db of attenuation, and the signal drops out of site, well, now its his receiver. He is very close to this 1320 signal.

Call KCTC, they should have a field strength meter that can locate the source of the signal.

In all cases, you have to let the group know what you find, when you find it.

tom bosscher k8tb, 40 odd, and very odd years in broadcasting.


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