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Problems with new BTE FM systems

G. M. Alf gmalf19 at gte.net
Tue Oct 7 11:07:57 EST 1997


On 5 Oct 1997 17:00:40 -0700, deeannwilson at SPRINTMAIL.COM (Dee Ann
Wilson) wrote:

>We are experiencing difficulties with equipment from two of the manufacturers, where the 
>receivers pick up a static sound, then briefly cut-out. This seems to be occuring 
>randomly, without regard to position relative to the transmitter, etc. We have explored 
>possible causes such as batteries/charge, frequency/channel settings, and more. As near 
>as we can tell, it seems to have something to do with the internal squelch adjustment. 
>One manufacturer has sent us a few receivers with the squelch adjusted as well as some 
>with the squelch completely de-activated, and that seems to help. 
>
>We are only having troubles with the newest models (AGC circuits) but have not had 
>similar problems with our older, linear models.
>
>Has anybody else experienced this type of problem? Did you ever find the cause? Any 
>advice?
>
>Dee Ann Wilson
>Wake County Public Schools
>Raleigh, NC
>
>email: deeannwilson at sprintmail.com
>
If you know someone with a scanner that has a search feature you might
have them show you how to search around the frequencies the FM units
operate.  There may be a strong RF source near the school such as a
police dispatch station, pager transmitting site or some such thing.
The problem may be eliminated by changing the frequency of the FM
units.

The clue is that distance from the transmitter doesn't seem to matter.
Bleed over from high powered (relatively) RF sources can do strange
things to squelch circuits.

If both the older and newer systems are operating on the same
frequency the problem may be due to the newer receivers being less
selective, again assuming bleed over.

Mike




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