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FAQ

 

Some frequently asked questions:

Why do I hear other people talking on my (LTR) radio system?

To understand this phenomenon, you must first understand a little of how LTR works.  In a trunked system, users are constantly being moved around between channels.  In fact, each time a user keys his radio, he may be on a different channel.  LTR, then, is the squelch that prevents you from hearing other users and vice versa.  Now, if we make that squelch too restrictive (tight), then a user may get cut off in mid sentence if his signal gets too noisy or he (or she) speaks a little too loudly into the mike (talk off).  So we "program" the LTR that if a user suddenly disappears for less than one second, hold the squelch open awaiting his return.  This can cause a burst of noise (or another user) to be heard during this one second interval.  So why doesn't this happen every time a user un-keys?  Because a special code (called a code 31) gets transmitted at the end of each transmission.  This code 31 tells the system that the user is finished talking and the "squelch" should be closed immediately.  In a perfect world, the code 31 would be received every time the user un-keys, but in reality, it gets missed about 10 to 20 percent of the time.  That is why the "other voices" come through, along with the occasional noise.

Why is it that sometimes I can't get a beep (LTR)?

There can be many reasons for this, here are just a few:

 
Atmospheric conditions can cause signals from other far away systems to travel into our system.  Since World Trade is especially high (1,350 feet), it is particularly sensitive to this phenomenon (called tropospheric ducting).  If the access problem occurs infrequently, particular during summer heat waves or during times of unstable weather.  As a further check for this situation, try listening to your FM car (or home) radio.  If you are hearing interference with stations that you normally can hear, or are picking up distant stations which you normally cannot hear, then you can suspect this phenomenon.

 

The system may be temporarily busy when you try to gain access.  If the problem recurs regularly at the same times and on the same days, this may be the problem.

If the problem is worse in bad weather, then there is a possibility of rainwater getting into you antenna system.  In a mobile, this generally occurs right at the base of the antenna, where it meets the vehicle.  Check to see that the rubber gasket located under the mount is still in place.  While you have it apart, also look for rust and/or corrosion.  The metal around the 3/4 inch hole should be cleaned right down to the bare surface.  Then put a light coating of vasaline to prevent water from contacting the bare metal.  Next install the captivating brass nut with the rubber gasket in place.  Here are a couple of additional tips which can improve the performance of your fleet:


Check your ground!  If you do not have a good electrical ground at the transceiver, then the radio will be relying upon the antenna cable for its ground.  This is not desirable as it will cause deterioration of the antenna cable and corrosion at the base of the antenna.  Do not rely upon the mounting bracket to provide your ground either; put the black wire directly to the negative battery terminal (or to the chassis of the vehicle).

 

Check you power wiring!  We just spoke about the ground but the positive leg is every bit as important.  Do not use a cigarette lighter plug for a two way radio.  They are only intended for temporary usage.  A UHF radio (especially a high powered one) should be wired directly to the battery leads and fused right at (or near) the battery.  Wiring the radio to any other point (such as the fuse block) is not recommended, due to voltage drops being introduced along the way.  Also, relying upon the mechanical integrity of a vehicle (especially an older one) to provide your electrical ground is also not recommended.

We will be happy to post other FAQ's and helpful information.  Please leave us your feedback.