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multi path

T

THEBIGONE

Guest
A question for Engineers.

I have a class A FM in Northeast PA. There are Multipath issues. I hear three sides to the story: 1) There nothing that can be done short of a power increase or tower move. 2) If the processing is driven hard it will mask or make less noticeable in areas of multipath. 3) Roll off the highs so that when the receiver is in a multipath area that this setting will soften the spitting with the receiver going in and out of stereo.

Please help me with what you have discovered. Thanks
 
As a test you might turn off your stereo generator (including the pilot) and transmit in monaural. The smaller r-f bandwidth of mono vs stereo should help reduce multipath distortion.
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I doubt changing your processing is going to help. If you are in a mountainous area multipath is a way of life. I would make sure your transmitter is operating correctly - tuned for minimum AM noise (maximum bandwidth). Also, if the antenna has a bandwidth problem it can make your signal sound like it has a multipath. STL performance is an issue also. Find someone who can perform an audio and RF proof to make sure you don't have a transmission chain issue before considering a tower move.
 
I have to agree about the options given above. I thought we were suffering from a major multipath problem. Turns out, yeah, we do have some multipath but it was worsened by a noisy STL and distortion in the xmtr.

Good idea to check the audio first.
 
My experience with multipath is that reality is rarely what is predicted. One might think that an increase in power will make the situation better, but sometimes it makes it worse. A change in transmit antenna location might improve signal in one area, but make it worse in another. A change in processing can make a difference, but again, I have seen this be unpredictable. Not only the hills will make a difference, but the change in seasonal foliage will make a difference. I would not turn off your stereo generator--this is 2006, not 1958--people expect a certain level of audio quality.
Some stations have attempted a booster station, but that is very tricky, and expensive.
I have had RF studies done (at great expense) to correct multipath problems, only to discover that they were wrong.
You will have to experiement some. The terrain is hilly there, so there are going to be issues. Try the easy stuff first, like subtle changes to your audio processing. Just don't get so crazed that you destroy your audio product trying to get your signal into some valley. If your multipath problem is in some populated area (i.e. where you could make some real money) a more expensive option might be to adjust your transmitting plant/antenna/tower location.
Or, adjusting your business model to compensate for the laws of nature might be a whole lot cheaper.
Good luck.
 
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