A single frequency issue like that also can be handled with a simple trap. A small coil with a capacitor across it tuned to the station's frequency at 91.1 MHz in series with the center conductor of your coax.
73, Ron AC7AC -----Original Message----- Jon, I had a similar problem with a 50 kW AM BC station a few miles away. It turned out to be strong enough to override the bias in the K3's T/R switch. I built a high-pass filter which solved the problem. You would need a low-pass filter in your case. Make sure it can handle 100w, because you must connect it in the main antenna path -- the RX in/out path is before the T/R switch. 73, Vic, 4X6GP/K2VCO Rehovot, Israel http://www.qsl.net/k2vco/ On 10 Feb 2016 16:58, Jon Zaimes wrote: > I had been noticing some RFI on 12 meters for some time that I > initially had thought was power line noise. My use of 12 meters is > seldom so it wasn't very high up on the list of things to track. > > When I was reminded of it while listening for VP8STI recently, I did a > little more snooping and realized it was actually splatter from a BC > signal at the low edge or slightly below the 12 meter band, centered > about 24.89 mHz but audible from 24.87-24.91 mHz. > > The distorted splatter is audible as a BC station, all talk, no music, > but not clear enough to decipher any ID. > > A few days ago I decided to try to pinpoint the source, so listened to > the RFI on one ear while scanning the AM and SW bands with the sub RX > on the other ear. But I could find no matches, though did find the > splatter popped up centered on these additional frequencies: > > 813 kHz > 996 kHz > 2.820 mHz > 3.626 mHz > 19.4 mHz > > Figuring it must be an FM BC station, I started going through a list > of Delaware FM stations and on the third one, 91.1 mHz, matched the > audio peaks to my splatter. Further research determined this was a > public radio station with a transmitter on a commercial tower just a half mile west of my QTH! > While I of course was aware of the tower, which I knew to carry a > couple of cell sites and trunking radio, I hadn't been aware of the FM > station, which has apparently been there about 2 years. FCC data shows > it has 2.1 KW ERP. I had not had any previous issues with the site over the past 17 years. > > Thinking that mixing or rectification might be produced either at the > TX site or on my own QTH, I decided to track with my mobile rig, an > IC-706 MK2G. But there was NO evidence of the splatter on the 706. > > Further debugging found that I was hearing the same splatter on BOTH > of my > K3 radios (no. 3021 and 3057). Even when ALL cables are removed (only > the power lead connected). Grounding or ungrounding made no change. I > tried the radios on a battery but still had the RFI. Tried some > ferrites on the power lead but no change. > > > So I'm thinking now there's some internal mixing in the K3 going on, > and wondering if any others have had similar issues and found any solution. > > 73/Jon AA1K > Felton, Delaware > www.aa1k.us ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
