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Strange stereo reception on old FM tuner
Strange stereo reception on old FM tuner
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Old 7th August 2018, 12:32 PM   #11
DF96 is offline DF96  England
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A mono receiver may not be able to recover the L-R signal, but it is still there in the modulation so it could affect things. The problem with FM is that to get a good linear demodulation you don't just need a linear discriminator but also a suitably smooth IF phase response over more or less the whole signal bandwidth. A mono receiver will have insufficiently smooth IF phase response over the bandwidth of a stereo signal so the signal entering the discriminator will be distorted. Whether this is the cause of the problems reported I don't know, but it would be naive to assume that because the L-R cannot be recovered that it cannot do any harm - especially when it is unusually strong.
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Old 7th August 2018, 01:07 PM   #12
Speedskater is offline Speedskater  United States
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Quote:
Originally Posted by davidsrsb View Post
A mono receiver has no way to recover the L-R signal, so there must be something not right with your stereo modulator.
Yes, I agree. It is an FM signal after all.
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Old 7th August 2018, 01:23 PM   #13
Pano is offline Pano  United States
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Strange stereo reception on old FM tuner
It should be easy to test. Game to try?
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Old 12th August 2018, 03:35 AM   #14
ejp is offline ejp  Australia
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Quote:
Originally Posted by davidsrsb View Post
A mono receiver has no way to recover the L-R signal, so there must be something not right with your stereo modulator.
A mono receiver has nothing but possibly limited IF bandwidth and de-emphasis *preventing* it from receiving the L-R informaton. It won't demodulate it, but it will reproduce it to some extent, and the sound resulting is heavily intermodulated. I've heard it
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Old 12th August 2018, 03:42 AM   #15
ejp is offline ejp  Australia
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Quote:
Originally Posted by DF96 View Post
What is simply untrue?
What is simply untrue is the statement that to get good mono reception from a stereo signal you need a stereo decoder set to mono. All you need is really good filtering above 15KHz.
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Old 13th August 2018, 09:15 AM   #16
DF96 is offline DF96  England
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I didn't say that you need a stero decoder set to mono; I said you need a stereo receiver set to mono. This is in order to get an IF response which is sufficiently phase linear across the required stereo IF bandwidth to avoid FM distortion in the IF, and a discriminator with sufficient bandwidth not to be pushed into nonlinearity by signals it was not designed to cope with. Whether or not there is a stereo decoder is irrelevant, which is why I didn't mention it.
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Old 13th August 2018, 09:46 PM   #17
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Strange stereo reception on old FM tuner
Quote:
Originally Posted by davidsrsb View Post
A mono receiver has no way to recover the L-R signal, so there must be something not right with your stereo modulator.

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