Ramsey Electronics FM25A Instrukcja Obsługi Pobierz pdf (Strona 25)

FM25A • 25

chart to show the maximum permitted performance of a non-licensed FM band

transmitter. The theoretical figures assume a simple 1 meter receiving antenna

in all cases and do not take into consideration that reception can be greatly en-

hanced with larger, multi-element antennas and preamplifiers. In the following

chart, the field strength (theoretical minimum) gets even stronger as you move

from the edge of these circular boundaries toward the antenna:

This "exercise in meters and microvolts" demonstrates that the FCC clearly in-

tends to limit the theoretical range of non-licensed devices operating in this

band. It also shows the potential for causing interference at a home down the

street from you. But it also shows that you can legally put out quite a good sig-

nal over wider areas than you might have imagined.

For other kinds of radio services, the FCC restricts such factors as transmitter

power or antenna height, which cannot really limit the possible "range" of a

transmission under good conditions. By restricting the maximum field strength

at a specific distance from your antenna, the FCC clearly plans for your signal

to "die out" at a specific distance from your antenna, no matter what kind of

transmitter power or extra-gain antenna you are using. On the other hand, the

FCC standards do make it legal and possible for you to broadcast on a school

campus, campground or local neighborhood, as long as you do not cause inter-

ference to broadcast reception.

“Why talk about acres"?

METERS FEET FIELD TOTAL AREA

3 10 250 314 FT

6 20 125 1256 FT

12 39 63 4800 FT

24 78 31 19113 FT

48 157 15 1.8 ACRES

96 315 7.5 7.2 ACRES

192 630 3.8 28.6 ACRES

384 1260 1.9 11.4 ACRES

768

2520

.95 458 ACRES

1536 5036 .5 1830 ACRES

DISTANCE FROM TRANSMITTER ANTENNA

1 2 ... 20 21 22 23 24 25 26 27 28 29 30

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Ramsey Electronics FM25A Instrukcja Obsługi Strona 25