Re: FM transmitter wanted with more power

Mebart wrote: 
You should be able to get much more than 15 feet range and still be
within the law.

Ramsey used to make a very high quality part 15 transmitter, but it is
pricey.

With 100 milliwatts and a 3 meter antenna, you should be able to do
300 to 500 feet with a decent receiver.

I'm assuming you want a real FM transmitter, capable of doing stereo
with good frequency stability (quartz based frequency).

If you just want someting to make noise with, there are many
schematics and products you can buy and operate legally. But, you will
have to chase the signal up and down the FM band unless you get one
that uses a quartz crystal to determine it's transmit frequency.

GL.


Actually, the rules permit 100 mW and a 3 meter antenna (combined with ground and feeder) on the AM broadcast band (525 - 1705 kHz), but not in the FM broadcast band (88 - 108 MHz). For the latter, the rules state:

[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.239]

[Page 816-817]

                       TITLE 47--TELECOMMUNICATION

              CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION

PART 15_RADIO FREQUENCY DEVICES--Table of Contents

                     Subpart C_Intentional Radiators

Sec. 15.239  Operation in the band 88-108 MHz.

    (a) Emissions from the intentional radiator shall be confined within
a band 200 kHz wide centered on the operating frequency. The 200 kHz
band shall lie wholly within the frequency range of 88-108 MHz.
    (b) The field strength of any emissions within the permitted 200 kHz
band shall not exceed 250 microvolts/meter at 3 meters. The emission
limit in this paragraph is based on measurement instrumentation
employing an average detector. The provisions in Sec. 15.35 for
limiting peak emissions apply.


It is paragraph (b) above that is the stickler. It takes only about 20 nanowatts into an efficient antenna (say, a quarter or half wave) to get that 250 microvolts/meter at 3 meters. Of course, you could use a kilowatt into a really bad antenna so long as you don't produce a field greater than 250 microvolts/meter at 3 meters.

Sorry to be the bearer of bad news.

John
.

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