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[Yaesu] FT-1000MP Sub-receiver Spurious Response

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Subject: [Yaesu] FT-1000MP Sub-receiver Spurious Response
From: geraldj@ames.net (Dr. Gerald N. Johnson, P.E.)
Date: Sat, 17 Oct 1998 17:17:50 -0500
Its sometimes hard to detect wide band FM signals in a narrow band
receiver. It just sounds like noise. The spectrum should be at least 75
khz because the broadcast FM signal is up to 150 Khz wide at full
modulation (75 khz deviation). Sometimes you can detect changes in the
noise amplitude and correlate them with modulation on a suspected
source. Occasionally such a station might let the modulation be quiet
for seconds and you can find a noisy carrier, but modern FM stations
tend to not let the modulation fall below 50% for any reason... Unless
something is broken.

Sounds as if the sub receiver in the FT-1000MP isn't shielded or has
slot(s) in the shield long enough to act as antenna(s) at 3 meters.

Twice the LO frequency is going to be strong in the mixer. 2nd order
mixer products tend to be strong.

Maybe the sub receiver needs a low pass filter at the input to it mixer.
Say something like a Drake TVI filter, though huge inside the radio
would be appropriate. Maybe the ground of a cable isn't connected

I don't have any HF Yaesu gear. I did notice while tuning the ten meter
band with my Corsair II sitting very near a TV set that its LO caused
bars on some VHF channels.

73, Jerry, K0CQ

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