I have FM transmitter and sometimes listen to music on my boomboxes this way.
One of my very early 60's mono boomboxes sounds like it's only receiving one channel but only with some songs. When I turn on/off R and L channel on transmitter, it corresponds properly to both channels so I'm at the loss why is that happening. Could it be that if a song has wide instrument separation like vocals in the left -music in the right, that the old tuner could somehow not handle it?
Not a big deal, just curious if anyone experienced that, guess you'd have to be a collector of old 🙂
One of my very early 60's mono boomboxes sounds like it's only receiving one channel but only with some songs. When I turn on/off R and L channel on transmitter, it corresponds properly to both channels so I'm at the loss why is that happening. Could it be that if a song has wide instrument separation like vocals in the left -music in the right, that the old tuner could somehow not handle it?
Not a big deal, just curious if anyone experienced that, guess you'd have to be a collector of old 🙂
Early mono FM receivers may have insufficient IF bandwidth for a stereo signal. Although they will get the baseband mono signal, they may add distortion from the multiplex signal they cannot properly receive so cannot properly ignore. To get good mono reception of a stereo signal you need to use a stereo receiver switched to mono.
Perhaps the LO is shifted and then the signals enters in the IF tranny one side away (laterally) in place of well centered.
Yeah sounds more like it just can't come with wide stereo images. The LO shifting part I have no idea. But I was curious about it because I like to listen to it. Lot of the early players have a very nice sound. I don't mean HIFI like, just very pleasant.
If the 19KHz pilot is not getting turned into the 38KHz tone for the L-R demodulator ( for whatever reason ) then the L+R won't be able to be mixed with the L-R signal to get L and R separate signals and you will only get L+R on both the L and R channels. (acting as a mono FM receiver)
This is simply untrue. A mono FM tuner may have *too much* audio passband, and the answer is to filter *out* the 19KHz pilot tone and the 23-53KHz difference information from the detected signal before letting it out of the tuner. A stereo demultiplexer is not required. This kind of compatibility was a requirement when the FM stereo system was chosen in 1961.
What is simply untrue? I saidejp said:
which is true.DF96 said:
You are raising a separate issue, which is pilot tone etc. getting out because of too much audio bandwidth.
Some early 'stereo' mixes were actually two separate mono channels, each containing some instruments/voices. This maximises the L-R signal, which maximises any compatibility problems with receiving a stereo signal on a mono receiver. It was assumed that L-R would be smaller than L+R because in real stereo it always is.
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 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.
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
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.
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.
This is a distinction without a difference. There is no such thing as a stereo receiver that doesn't have a stereo decoder.