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Re: [RFI] AM Radio Interference On 75 meters

To: <k1ttt@arrl.net>, "RFI Contesting" <RFI@contesting.com>
Subject: Re: [RFI] AM Radio Interference On 75 meters
From: Joe <wa6rkn@gmail.com>
Date: Tue, 18 Sep 2012 10:15:40 -0700
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
----- Original Message ----- 
From: "David Robbins" <k1ttt@verizon.net>
Subject: Re: [RFI] AM Radio Interference On 75 meters


> 
> 3960khz is not a harmonic of 1530khz so something else is also happening 
> here.  listen carefully to the kfbk signal and see if there is some other 
> signal mixing with it.  check for other harmonics and other signals that it 
> might be mixing with to end up on 3960...
> 
> 1530 + 2430khz?
> 1530*2 + 900khz?
> 1530*3 - 630khz?
> 1530 + 2*1215khz? 
> 5490 - 1530khz?
> etc, etc.
> 
> Then it must be mixing somewhere.  add lots of attenuation, if the signal 
> suddenly dissappears its mixing in your radio... if not then its likely 
> outside, which you may have already confirmed by using other radios... 
> Yup..not in the radio...other radios brought to the location, both mobile and 
> fixed, exhibit the same RFI assuming they aren't overloaded the same way, you 
> don't say how far away you are or how strong the kfbk signal is at your 
> location by itself.  try driving around with a well attenuated mobile radio 
> and see if the signal gets stronger or weaker, is it there a long distance 
> from your home station?  Approximately 8 miles, give or take   if so it is 
> probalby not being generated near your station.  does it switch pattern or 
> power from day to night and does the signal appear/dissappear at the switch 
> time?  As stated in the original post..starts early evening, and goes away a 
> 6am   can other hams hear it inside the normal ground wave distance for 
> 3960khz? Some yes, others no.  can anyone get a bearing on it with a loop or 
> beverages or 4-square??  Will try that. can anyone hear it farther away at 
> night? Dunno lots of questions... 
> 
> 
> Sep 18, 2012 12:09:53 PM, wa6rkn@gmail.com wrote:
> 
> Here is the scenario. In the evening, through 6 am, radio station KFBK 
> Sacramento (1530 KHz) *blasts into 75 meters with a 25k wise signal at 3.960. 
> The signal is so stron, SSB conversations on 3.959 are impossible.
> 
> Notch and DSP filters in the radio do not work (Icom 757Pro) and other radios 
> set up at that location, either fixed or mobile, suffer the same issue.
> 
> Here is are 'RFI present', and 'RFI Absent' Videos to exhibit the problem. 
> 
> Interference Present: 
> http://s1255.photobucket.com/albums/hh635/WA6RKN/?action=view¤t=RFIPresent.mp4
> 
> Interference absent:
> http://s1255.photobucket.com/albums/hh635/WA6RKN/?action=view¤t=RFIAbsent.mp4
> 
> Any suggestions? Nothing has helped so far...line chokes, coils, Band pass 
> filters, etc.
> 
> Definitely a 3rd order harmonic..Radio station is blowing off the complaint, 
> so a formal complaint has been filed with the is so bad, we cannot 
> communicate with the involFCC, but that will umpteen years to get acted upon. 
> (: It is so bad, we cannot communicate with ham involved! 
> 
> Thanks in advance for any help and suggestions.
> 
> Joe Wolfe
> WA6RKN
> 
> 
> 
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