[RFI] Splatter from AM Radio Station

[Lee STRAHAN]

Nope Al,
   One of the high level repeaters in Portland Oregon is situated in a Washington state facility right across the Columbia river on a mountain top. There were at one time 46 repeaters in that facility including the Portland Amateur Radio Clubs 146.840 Machine. Among those 46 repeaters were 2 commercial repeaters on 450 MHz that were exactly 600KHz apart. When and if they both transmitted at the same time  and the 2 meter carrier was up we called it "The dying dinosaur" from the awful howl feeding the repeater RF output and subsequent audio right back into and out of the receiver. 
   An astute ham friend that also worked on the other commercial repeaters retuned the 450 MHz filter system and eliminated our problem. 
      Just as an aside the 222 MHz band has a similar problem with commercial FM broadcast transmitters at 1.6 MHZ apart. Eventually in this high RF area I had to separate the TX and RX antennas on my 222 MHz machine to get enough isolation even with using a good duplexer.
Lee  K7TJR  OR

-----Original Message-----
From: RFI <rfi-bounces+k7tjr=msn.com at contesting.com> On Behalf Of Al Groff via RFI
Sent: Thursday, October 28, 2021 1:20 PM
To: rfi at contesting.com
Subject: Re: [RFI] Splatter from AM Radio Station

John,
   I thought the 600 Khz /2m repeater intermod problem was unique to Cedar Rapids (WMT AM 5kw 600 Khz).
Several of the 2m repeaters here are split site with UHF Link between the RX and TX sites because of the 600Khz problem.
73
AL, K0VM


On 10/27/2021 6:51 PM, John Brodie wrote:
> Think of the intermod fun we have at VE7SAR with a 100kw AM broadcast 
> station a few km away on 600 KHz, the offset frequency of our repeaters.
> Only way to make the howls tolerable was to turn off the CTCSS tone on 
> the output of the repeater, which at least stopped the mixed signal 
> from feeding back to the input.
>
>   
>
> John Brodie VA7XB
>
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