----- 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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