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Antenna advice please

E

Eric R Snow

Jan 1, 1970
0
Greetings,
I'm sure this is a pretty basic question. Which is good because my
knowledge of electonics is pretty basic. 30 years ago I bought a CB
radio, antenna, and an SWR meter. I believe SWR stands for Standing
Wave Ratio. Anyway, this meter was for matching the antenna to the
radio. Changing the position of the antenna on the car would affect
the match. Now, I have an FM transmitter that I bought as a kit from
Ramsey. It works well with included telescoping antenna. As long as
the radio is within about 80 feet. The transmitter is used to listen
on the radio to stations broadcasting on the web. The location of the
antenna is pretty close to the center of a 10 acre parcel that is
about 1000 feet long by 450 feet wide. The ideal antenna would be one
that broadcasts in a rectangle of the same proportions so as not to
break any FCC rules.So what I would like are pointers to likely
antennas and how to build the SWR meter. I've googled but haven't been
able to find something simple enough for me to understand. Any ideas
are very welcome. I'm a machinist with many years experience so if
anyone has any metalworking questions I'd be happy to try to come up
with a good answer.
Thanks,
Eric R Snow,
E T Precision Machine
 
P

PN2222A

Jan 1, 1970
0
Eric R Snow said:
I have an FM transmitter that I bought as a kit from
Ramsey.
The ideal antenna would be one
that broadcasts in a rectangle of the same proportions

Well, good luck on that one. Easier to arrange for it to rain
only on 1/2 of your lot!
so as not to
break any FCC rules.

Unfortunately, modding the transmitter or the antenna will
violate the part 15 rules for this device.
Extending the range from 80 feet to 330 feet will require more
power. Which won't be within the regs.
So what I would like are pointers to likely
antennas and how to build the SWR meter.

Sorry, Eric. Your transmitter doesn't produce enough
power to move the needle on any SWR bridge (passive) that you
can build.

The good news is that there's no real benefit to matching the antenna
and line on a tiny TX like this.

Regards
PN2222a

Let me introduce my partner,
2N2906.
 
E

Eric R Snow

Jan 1, 1970
0
Well, good luck on that one. Easier to arrange for it to rain
only on 1/2 of your lot!


Unfortunately, modding the transmitter or the antenna will
violate the part 15 rules for this device.
Extending the range from 80 feet to 330 feet will require more
power. Which won't be within the regs.


Sorry, Eric. Your transmitter doesn't produce enough
power to move the needle on any SWR bridge (passive) that you
can build.

The good news is that there's no real benefit to matching the antenna
and line on a tiny TX like this.

Regards
PN2222a

Let me introduce my partner,
2N2906.
The instructions from Ramsey state that other antennas can be used
with this transmitter without violating FCC rules. Most important is
to keep the signal within my property.
ERS
 
J

John - KD5YI

Jan 1, 1970
0
Eric said:
The instructions from Ramsey state that other antennas can be used
with this transmitter without violating FCC rules. Most important is
to keep the signal within my property.
ERS


Most important is found in paragraph (b) below. This means you can use any
antenna you like, as long as your field strength (in any direction) does not
exceed the value specified below.


[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.
 
E

Eric R Snow

Jan 1, 1970
0
Eric said:
The instructions from Ramsey state that other antennas can be used
with this transmitter without violating FCC rules. Most important is
to keep the signal within my property.
ERS


Most important is found in paragraph (b) below. This means you can use any
antenna you like, as long as your field strength (in any direction) does not
exceed the value specified below.


[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.
Greetings John,
Of course you're correct. The FCC can't use the size of a piece of
land as a gauge. And I seem to recall reading that even if the power
does not exceed the above it must still not interfere with someone
else recieving radio signals.
Eric
 
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