--- In Repeater-Builder@yahoogroups.com, Ken Arck <[EMAIL PROTECTED]> wrote:
>
> Have a customer with the following issue:
>
> Scenario: Amateur repeater (Mastr II) installed at a 100,000 FM
radio
> xmtr site.
>
> Issue: Very low level audio of radio station appears on Mastr II's
> xmtr (yes, external controller). Repeater owner hasn't fully
> explained what "very low level" means. But regardless.....
>
> Question: The only way I see this happening is due to some AM
> component on radio station's transmitter.
>
> Thoughts?
>
>
Thoughts?????
I haven't seen it mentioned yet, but yes, this sounds like a classic
case of Intermood.
The repeater antenna and feed line are passive items, meaning that
they don't do anything but sit there with the ability to transmit
and receive on different frequencies at the same time!
The FM station's 100KW signal comes into the repeater's coax from
the antenna, mixes in the repeater's finale which is a nonlinear
class C circuit, and gets transmitted on the repeater's output.
IF this is the case, a cavity filter tuned to the FM station's
signal, at the botom of the coax at the repeater's output, should
take out the offending signal. This can be built out of a large tin
can, per data on the Internet. Suggest starting with 2 number 10
tin cans stacked and soldered together for that frequency, which
would be bigger than one number 10 cavity, made for 2 meters or
above.
Also to consider, having a 100KW FM broadcast signal right next to a
antenna, coax, and repeater receiver rated in the microvolt region,
is a lot to expect, overloading the receiver and probably also
causing desence in the repeater receiver. A cavity at the repeater
receiver, also tuned to the 100KW FM station's carrier, should solve
that.
"Been there, done that!"
Best wishes,
Dick, W7TIO (retired Mobile Radio Communications tech.)
Ken
> -------------------------------------------------------------------
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