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Old Sony FM Table Radio IF Rejection

The technical side of broadcasting. Think IBOC is a sham? Talk about it here! How about HDTV? Post DX reports here as well.
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Ben Zonia
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Joined: Sat Jun 03, 2006 10:35 pm
Location: Honor

Old Sony FM Table Radio IF Rejection

Unread post by Ben Zonia »

Has anyone here had a problem with IF rejection from strong FM signals 10.4 or 11.0 MHz apart?

I had a professor who was within a mile of two stations 10.4 MHz apart at his office, and he had a Sony Table radio where he had all kinds of blanketing and overload problems. The engineering tech put two LCs on the back of the radio connected to each side of the 300 Ohm antenna input. He had a double folded dipole turnstile antenna on the roof. The engineer detuned both sides with the LCs on the balanced antenna input. But it occurred to me that if the receiver had a really wide IF stage, 10.4 and 11.0 MHz might be a problem in such cases. The radio was from the late 1960s. It looked SOMETHING like this.

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TC Talks
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Re: Old Sony FM Table Radio IF Rejection

Unread post by TC Talks »

No, but I did sleep at a Holiday Inn Express last night.
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Ben Zonia
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Re: Old Sony FM Table Radio IF Rejection

Unread post by Ben Zonia »

As irrelevant and impertinent as your comment seems, I did stay at a Holiday Inn near LAX once, and I couldn't get KOST 103.5 on the hotel alarm clock radio, because the 103.1 and 103.9 transmitters were so close. It was within the Los Angeles City Limits, and clearly LOS from Mt. Wilson.
"I had a job for a while as an announcer at WWV but I finally quit, because I couldn't stand the hours."

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SolarMax
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Re: Old Sony FM Table Radio IF Rejection

Unread post by SolarMax »

Sometimes, a simple inline attenuator like the "DX/Local" switch available on some (but too few) radios, will knock the stronger offending signals down just a few dB, enough to allow copy of the station you actually want to hear. Or, if there's a wire for an FM antenna, shorten it as much as needed to keep the good, reject the bad.
k8jd
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Re: Old Sony FM Table Radio IF Rejection

Unread post by k8jd »

Sounds like his antenna system for the table radio was overkill for local reception and probably overloading the thing.
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WOHO
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Re: Old Sony FM Table Radio IF Rejection

Unread post by WOHO »

Have a Sony very similar, just 2 pieces of #12 wire 15" long make a pretty dandy FM antenna on a tabletop radio (although not pretty).
Japanese quality, which means it still works, but has the scratchy controls, including tuning cap.
Using it in a basement, so no overload issues there.
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