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FM Transmitter Antennae


captainron19

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Steven wrote:

PMC wrote:
My FM transmitter is FCC Part 15 compliant

Part 15 says that an FM transmitter must not exceed 150 μV/m measured at 3 meters [from the antenna]. How did you ensure that your system meets those requirements?

Its actually 250 uV/m but whats 100 uV/m among friends...:cool:
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Surfing4Dough wrote:

Page 18:

http://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet63/oet63rev.pdf

What is the "periodic" transmission listed just above ours? I only transmit periodically (suspect it means something different though).


I guess this is what disqualifies us from "periodic" transmission:

§ 15.231 Periodic operation in the band 40.66–40.70 MHz and above 70 MHz. (a) The provisions of this section are restricted to periodic operation within the band 40.66–40.70 MHz and above 70 MHz. Except as shown in paragraph (e) of this section, the intentional radiator is restricted to the transmission of a control signal such as those used with alarm systems, door openers, remote switches, etc. Continuous transmissions, voice, video and the radio control of toys are not permitted. Data is permitted to be sent with a control signal. The following conditions shall be met to comply with the provisions for this periodic operation:
(1) A manually operated transmitter shall employ a switch that will automatically deactivate the transmitter within not more than 5 seconds of being released.
(2) A transmitter activated automatically shall cease transmission within 5 seconds after activation.
§ 15.231 Periodic operation in the band 40.66–40.70 MHz and above 70 MHz.
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Steven wrote:

PMC wrote:
My FM transmitter is FCC Part 15 compliant

Part 15 says that an FM transmitter must not exceed 150 μV/m measured at 3 meters [from the antenna]. How did you ensure that your system meets those requirements?

If you look at the attached pic you will see my transmitter on the left side and coming out of that box is a white wire, that's the antenna for that Part 15 transmitter, if you attach any other antenna to that white wire you are no longer compliant, so I wrapped the wire around a dipole (not attached to it) as long as you don't modify its FCC legal


Attached files 307610=16851-Box+Antenna.JPG
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so what you're saying, i think, is..you have a part 15 certified transmitter, have not modified it, so it remains certified, and so are assuming you are compliant, meaning, not exceeding the 250 uV/m limit.

But, you have not actually conducted field strength measurements to confirm?

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DonFL wrote:

so what you're saying, i think, is..you have a part 15 certified transmitter, have not modified it, so it remains certified, and so are assuming you are compliant, meaning, not exceeding the 250 uV/m limit.

But, you have not actually conducted field strength measurements to confirm?
there is a sticker on the back of my transmitter that says the FCC ID, which is good enough for me. (picture attached) you can see the yellowing of the paper to see how old this unit it is, this FCC certification ID sticker is equal to the UL sticker on electrical devices, which means it was tested by a company that approved it was Part 15

If you FM Transmitter doesn't have or provide a FCC ID number, chances are its not compliant, but if your willing to pay......

the Potomac Instrument needed to calculate the the field strength cost more than I'm willing to pay and that's the one that the FCC uses.

here's one for $300 (I never used it, probably never will)



Attached files 307644=16855-FCCID.JPG
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I need to make a correction,
The $300 unit is for High Frequency (not analog FM)

Radio frequency field strength meter for mobile phones, cell phone base stations, microwave leakage, and other areas where high frequency signals are used.

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1) Adding an external antenna to any of these transmitters, other than using the whips/wires they were designed with, makes them non compliant with part 15.

2) While you are not likely to have an issue if your transmitted signal goes a little farther than it should (as long as there are no interference complaints from neighbors), you most definitely will have an issue if you are discovered to be operating well beyond part 15 allowances (ie 1 watt and higher units), complaints not withstanding.

Greg

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PMC wrote:

I need to make a correction,
The $300 unit is for High Frequency (not analog FM)

Radio frequency field strength meter for mobile phones, cell phone base stations, microwave leakage, and other areas where high frequency signals are used.

Gotcha on this one Paul. And mind you, I am just messing with you all in good fun. Now H.F. is 3-30Mhz. Mobile phones, cell phones, and microwaves are anything but H.F. Can we say UHF and SHF? And surely not ELF. Ok, enough fun for now..

In Truth, Paul I was trained to work on the stuff you get to play with daily. But after coming out of the Air Force, I just did not find any work that paid me what I was worth back then.
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very true, but this meter was out of range for analog FM, and if I didn't correct it. I knew somebody with notice it

I have a meter for © as well as (L) band and (ka & ku)

my STL's are on 11 and 14 Gig frequency (very stable)

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OK you brainiacs! I have a question over this subject of FCC regulations... I want to buy an EDM transmitter.. Only issue.. I live about 3/4 mile from a small airport...
Any suggestions.. Sorry not trying to still a thread.. Just saving paper!

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Use the supplied wire antenna indoors, don't overdrive the audio into the transmitter from your pc, be sure you are on a clear frequency, and you will be fine.

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So aslong as i dont overdrive the audio I wontb have the mini airport lamigre on my doorstep? Well i dont wanna use local channels.. of course. Just dont need barney fifie knocking while we are dropping yuletide jamz....

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hdracer wrote:

So aslong as i dont overdrive the audio I wontb have the mini airport lamigre on my doorstep? Well i dont wanna use local channels.. of course. Just dont need barney fifie knocking while we are dropping yuletide jamz....

For one thing FM transmitters do not ransmit in the same frequency as the radios in Aircraft which if I remember correctly is VHF.
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