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Author Topic: FM Tramitters  (Read 445 times)

Jesse Bastos

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FM Tramitters
« on: May 22, 2020, 03:21:56 pm »

I'm sure a lot of us will be involved in "Drive - in Concerts" this summer.   Any recommendations for Pro Level low power FM transmitters?
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Scott Holtzman

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Re: FM Tramitters
« Reply #1 on: May 22, 2020, 03:57:46 pm »

I'm sure a lot of us will be involved in "Drive - in Concerts" this summer.   Any recommendations for Pro Level low power FM transmitters?


Take a look, there is a long thread on this issue from Isaac South



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Scott AKA "Skyking" Holtzman

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Bill Meeks

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Re: FM Tramitters
« Reply #2 on: May 22, 2020, 04:27:37 pm »

For convenience, here is a link to the thread Scott is talking about:  https://forums.prosoundweb.com/index.php/topic,173767.0.html

The short summary is the only FM option is very low power with limited range of 200 feet or less, and that option is questionable in terms of FCC acceptance. This is because these devices are typically made overseas and lack an FCC certification.

Another option, that is legal in the United States, is a low-power AM transmitter. You will find a short discussion of that option and a link to the manufacturer's site in the linked thread.
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Tim McCulloch

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Re: FM Tramitters
« Reply #3 on: May 22, 2020, 05:10:42 pm »

For convenience, here is a link to the thread Scott is talking about:  https://forums.prosoundweb.com/index.php/topic,173767.0.html

The short summary is the only FM option is very low power with limited range of 200 feet or less, and that option is questionable in terms of FCC acceptance. This is because these devices are typically made overseas and lack an FCC certification.

Another option, that is legal in the United States, is a low-power AM transmitter. You will find a short discussion of that option and a link to the manufacturer's site in the linked thread.

That option requires a filing for a STA - special temporary authorization - with the FCC.  CP Communications can handle those details and rent the gear to you.  It will not be cheap, and the turn around time for the STA is 3-4 weeks.  The STA must be approved before they will ship the gear.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Jesse Bastos

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Re: FM Tramitters
« Reply #4 on: May 22, 2020, 08:45:43 pm »

For convenience, here is a link to the thread Scott is talking about:  https://forums.prosoundweb.com/index.php/topic,173767.0.html

The short summary is the only FM option is very low power with limited range of 200 feet or less, and that option is questionable in terms of FCC acceptance. This is because these devices are typically made overseas and lack an FCC certification.

Another option, that is legal in the United States, is a low-power AM transmitter. You will find a short discussion of that option and a link to the manufacturer's site in the linked thread.

Thanks Bill

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Jesse Bastos

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Re: FM Tramitters
« Reply #5 on: May 22, 2020, 08:46:32 pm »

That option requires a filing for a STA - special temporary authorization - with the FCC.  CP Communications can handle those details and rent the gear to you.  It will not be cheap, and the turn around time for the STA is 3-4 weeks.  The STA must be approved before they will ship the gear.

Thanks Tim.
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Bill Meeks

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Re: FM Tramitters
« Reply #6 on: May 23, 2020, 10:59:54 pm »

That option requires a filing for a STA - special temporary authorization - with the FCC.  CP Communications can handle those details and rent the gear to you.  It will not be cheap, and the turn around time for the STA is 3-4 weeks.  The STA must be approved before they will ship the gear.

Acording to the manufacturer/seller of the equipment, an AM system that is certified under Part 15 of the FCC regulations is okay without any special permits. Here is a recent interview with the seller of the AM system that was discussed in the linked thread:  https://www.radioworld.com/news-and-business/low-power-radio-faqs.

For FM, there is a limit on field strength, and that limit is so low as to make Part 15 FCC FM transmitters next to useless for anything much beyond 100-200 feet. However, for AM transmitters, the Part 15 limit is on transmitter power (100 mW or less) and antenna length. Due to the easier propagation of AM broadcast frequencies, you can get much longer range and still stay within the FCC limits. The only caveat is you must not cause interference to a local broadcast station with your low power system. However, you would usually choose an unoccupied frequency for your local area anway so that any local broadcast station would not stomp all over your little 100 mW signal.
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Tim McCulloch

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Re: FM Tramitters
« Reply #7 on: May 23, 2020, 11:09:12 pm »

Acording to the manufacturer/seller of the equipment, an AM system that is certified under Part 15 of the FCC regulations is okay without any special permits. Here is a recent interview with the seller of the AM system that was discussed in the linked thread:  https://www.radioworld.com/news-and-business/low-power-radio-faqs.

For FM, there is a limit on field strength, and that limit is so low as to make Part 15 FCC FM transmitters next to useless for anything much beyond 100-200 feet. However, for AM transmitters, the Part 15 limit is on transmitter power (100 mW or less) and antenna length. Due to the easier propagation of AM broadcast frequencies, you can get much longer range and still stay within the FCC limits. The only caveat is you must not cause interference to a local broadcast station with your low power system. However, you would usually choose an unoccupied frequency for your local area anway so that any local broadcast station would not stomp all over your little 100 mW signal.

When you said "low power" I interpreted that in the Broadcast sense of low power.  Units used in real estate ("talking houses") and to broadcast the sound track to holiday lighting displays ARE Part 15 compliant.  The partial solution to more coverage is to get the antenna up in the air but at some point the inverse square law dominates and there is no long enough RF.

If more RF is needed, an STA will be on the menu...
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

ProSoundWeb Community

Re: FM Tramitters
« Reply #7 on: May 23, 2020, 11:09:12 pm »


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