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Old August 28th 06, 02:28 AM posted to rec.radio.shortwave
Tom Tom is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 58
Default Local Interference


Kevin Garrett wrote:
Hi All:

I have a radio shack DX394 and an RF Systems EMF antenna. From about 7020
through 7180 or so I am getting interference from KYCH 97.1 FM. I can
recognize the song playing.

Is something likely wrong with my radio, antenna or is it them? Or could
it be that I am pretty close to their transmitter?

This is in Portland Oregon

Kevin


Kevin, this is VHF image interference related to the 1st IF of 45 MHz.
The 1st local oscillator is at 52.1 MHz to tune in 7.1 MHz- -
difference equals 45 MHz, but 97.1 MHz also produces a diff of 45 MHz.
While the DX-394 does have a filter in the Lo-Z input to suppress
signals above 30 MHz, its stop-band attenuation is not enough to
prevent strong VHF signals from breaking through. Add an ouboard 30-40
MHz lowpass filter in the coax line between the antenna and LO-Z input
to increase the VHF attenuation.

Also, for more info on the DX-394, join the user group at
http://groups.yahoo.com/group/RADIOSHACKDX394/ .

Tom