The field test has proven the effectiveness of the frequency locking method used in the Broadcast Electronics FX-30 FM Exciter Synchronous Booster design. It has shown to be a versatile, reliable, and noise immune method to frequency lock two or more exciters.
|
Preliminary testing tends to show the need for
15 to 20 dB of carrier ratio throughout the desired coverage area for quality reception.
For most stations considering the addition of a booster, this is not a problem, due to
extremely heavy main signal shielding by a natural barrier, such as a mountain. In such
locations, the interference zones should be fairly narrow, and will most likely occur in
unpopulated areas high atop the mountain. Localized main signal shielding, such as is caused by buildings or small valleys, is not adequate, and the addition of a booster will most likely create more interference outside of the immediate area than it will fix. IT IS IMPERATIVE TO NOTE THAT THE ADDITION OF A BOOSTER IS NOT A FIX FOR MULTIPATH. IT WILL ONLY MOVE THE PROBLEM SOMEWHERE ELSE, AND WILL MOST LIKELY CREATE MORE INTERFERENCE THAN IT WILL FIX. |
The width of interference zones is difficult to accurately predict, but in general, the better the degree of natural shielding, such as a mountain, the narrower will be the area.
Time delay equalization and deviation calibration of the modulation appear to be of limited value in most situations, but may have certain advantages, depending on the particulars of a given installation.
There are a variety of ways to configure a booster system. Some have been described in this paper, but many more ingenious ways remain to be found. The industry is encouraged to pursue different methods so that other economical and reliable systems may evolve.
It is important to remember that the field test results are for one station in one area, and that installations at other dissimilar locations may produce different results. However, at this time, this is the only basis on which to make predictions. We welcome the findings of other engineers on this subject so that we may continue to compile an accurate understandinq of this new and potentially advantageous field.