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GMRS / FRS - Discussions related to GMRS (General Mobile Radio Service) and FRS (Family Radio Service) communications

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Old 01-25-2018, 6:14 PM
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Default Roof mounted FRS radio?

Has anyone considered mounting the entire FRS radio on the roof, on a mast to overcome the antenna restriction? It seems this would not be too difficult using a PTT speaker/mic and remote power source and a weather proof enclosure. I don't think this would be illegal.
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Old 01-25-2018, 6:18 PM
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When I was at RS, we developed one. 21-1850




All the radio boards are in the antenna. The mic is just a controller.
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Old 01-25-2018, 6:23 PM
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Default Roof mounted FRS radio?

Quote:
Originally Posted by iMONITOR View Post
Has anyone considered mounting the entire FRS radio on the roof, on a mast to overcome the antenna restriction? It seems this would not be too difficult using a PTT speaker/mic and remote power source and a weather proof enclosure. I don't think this would be illegal.


Thats funny, Id like to see that go by one day on the interstate. Lol I have my mobile with all the FRS / GMRS channels in one zone along with all the GMRS repeater frequency pairs with the travel tone 141.3 in another zone.


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Old 01-25-2018, 7:36 PM
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Ha! They did this with the original Class B CB UHF radios in the 1950s. I think it was Vocaline that had a radio with attached antenna that mounted on your roof and a remote speaker and mic in the house.
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Old 01-25-2018, 8:16 PM
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Quote:
Originally Posted by UPMan View Post
When I was at RS, we developed one. 21-1850




All the radio boards are in the antenna. The mic is just a controller.
Actually that's what gave me the idea. But I was thinking of doing it on the roof of a house, and maybe a 10' mast!
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Old 01-25-2018, 8:40 PM
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A GMRS Small Base Station can already do this, at least on the first 7 shared FRS/GMRS channels.

You're allowed 5 watts ERP on those 7 shared channels, with a 20' height limit above ground (if the antenna is mounted on a ground mounted tower), or 20' above the structure on which it is mounted, such as the roof of your home.

All you'd need is a handheld radio, or a low power mobile radio (Midland produces both 5 watt and 15 watt GMRS mobile radios with channels 1-7 and 15-22), low loss coax, and a unity gain (quarter wave) or low gain antenna.

Remember, ERP is figured out by taking the power output of the radio, minus the loss in the coax in dB, plus the gain of the antenna in dB. A 10 watt radio feeding a quarter wave antenna with coax that has 3dB of loss will give you 5 watts ERP.

And I have 2 of those Radio Shack mobile FRS radios.

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Last edited by KB7MIB; 01-25-2018 at 9:31 PM.. Reason: Multiple fixes and additions
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Old 01-25-2018, 8:53 PM
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Quote:
Originally Posted by iMONITOR View Post
Actually that's what gave me the idea. But I was thinking of doing it on the roof of a house, and maybe a 10' mast!
Newer cellular base stations use a similar idea. RRU's, Remote Radio Units, is where the radio is mounted -at- the antenna and a hybrid cable where power and fiber is used to feed it from the ground. Work well since at cellular frequencies (700, 800,1900, etc) the coax losses can be high, and the 1 5/8" coax they often use is costly.

Many professional radios have connections on them that will allow some level of remote control. Setting up a simple mobile radio in a box at the base of the antenna fed with a tone remote and power would accomplish the same thing.

Or, just extend the speaker mic (3 conductor) from the ground up to the FRS radio at the antenna.

A fun exercise, but as stated above, just get your GMRS license and it's no longer much of an issue.
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