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Author Topic: GMRS (General Mobile Radio Service) Anyone?  (Read 396 times)

Doc Roads

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GMRS (General Mobile Radio Service) Anyone?
« on: May 13, 2020, 04:09:14 PM »
Anyone use this service?  I was scanning with my UHF/VHF HT and caught a signal at 462.550 MHz.  It was two operators testing out their channel 15 GMRS repeater. I had no idea there was a repeater in the area.  I listened and learned a bit about GMRS ... researched it on the internet and found out quite a bit about it.  This set of frequencies is reserved for personal use and the license you must get from the FCC covers the whole family.  Iíve had a hard time getting DW to get interested in passing the Ham Tech license but she has no problem using an FRS handheld but that has a very limited range .... so this may be an alternative for connectivity between vehicles, fishing trips, and longer distances without the CB color and chatter ... FRS and GMRS freqs overlap ... FRS is a couple watts and GMRS allows up to 50 watts on select freqs. Seems pretty capable and flexible ... anyone have anything to add?
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Gary RV_Wizard

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #1 on: May 14, 2020, 10:10:12 AM »
Many "walky-talky" type radios cover the channels in the GMRS spectrum, and few owners bother to get a license for them.  My Motorola Talkabouts are an example, but they are relatively low wattage (2W on GMRS?).  In practice, as long as they are only used for personal (family) communications and you aren't pumping out the max allowed 50 watts, I doubt if anybody would ever ask about having a license.
« Last Edit: May 14, 2020, 10:17:44 AM by Gary RV_Wizard »
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Larry N.

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #2 on: May 14, 2020, 11:07:12 AM »
Gary's probably right, but I would suggest that if you get radios other than the combo handhelds (FRS/GMRS) that you get the license. Those fines can be pretty steep sometimes, and the hassle alone would be less than pleasant.
Larry and Mary Ann N.
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Lou Schneider

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #3 on: May 14, 2020, 11:53:51 AM »
A GMRS repeater uses different frequencies to receive and transmit.  You need a radio that can do the same to use the repeater.

Inexpensive FRS radios can operate simplex on the same frequencies, so they can hear the repeater's output.  But they can't transmit into the repeater unless they're capable of split frequency operation.

Larry N.

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #4 on: May 14, 2020, 03:13:48 PM »
Excellent point, Lou -- I forgot to discuss the repeaters. They'll certainly want the license to use those.
Larry and Mary Ann N.
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2015 Wrangler Sahara Unlimited toad
Formerly: Trailmanor 2720SL, Bounder, Beaver
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Gary RV_Wizard

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #5 on: May 14, 2020, 07:06:03 PM »
Agree with the others - if you want to use high wattage GMRS or get access to the repeaters you mentioned, the license is really a must.
Gary
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HappyWanderer

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #6 on: May 14, 2020, 08:40:15 PM »
A GMRS repeater uses different frequencies to receive and transmit.  You need a radio that can do the same to use the repeater.

Inexpensive FRS radios can operate simplex on the same frequencies, so they can hear the repeater's output.  But they can't transmit into the repeater unless they're capable of split frequency operation.

An unlicensed operator could unknowingly cause interference by using simplex on the repeater input frequency. They would never hear the repeater and would be completely unaware of the interference.
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Doc Roads

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #7 on: May 14, 2020, 09:45:54 PM »
A GMRS repeater uses different frequencies to receive and transmit.  You need a radio that can do the same to use the repeater.

Inexpensive FRS radios can operate simplex on the same frequencies, so they can hear the repeater's output.  But they can't transmit into the repeater unless they're capable of split frequency operation.
Yes, in 2017, FRS use was approved for the GMRS channels but FRS transmitters are limited to not more than 2 watts or less ... FRS certified radios are not capable of using the repeater offset too and no license required.  BTW, make sure the GRMS radio you select can handle offsets, some don’t. I want to be able to talk short and long range via the repeater.  That’s the plus I see ... clear FM signal, repeater capability for good range, up to 50 watts transmitter power for more simplex range, no test for the DW to take, and at a reasonable price for me.  Jeep off-road clubs are moving from CB to GMRS for most of the same reasons.  CB is AM and inherently has more static ...

I plan to install a 15 watt mobile station in my MH.  Just working on the installation to be compatible with all the other “stuff” I have on top and in the overhead compartments.  I nominate channel 15 as the RV channel to monitor ... maybe there’s already one nominated!
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Doc Roads

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #8 on: May 14, 2020, 09:56:08 PM »
Hereís a quick comparison ...
What are some of the pros of GMRS over CB...
Power: CB is limited to 4 watts (AM) or 12 watts (SSB which most don't use offroad). GMRS can have up to 50 watts.
Modulation: CB is AM (typically used offroad, some CBs also have SSB, Single Side Band). GMRS is FM. Just like in your vehicle, FM has better audio quality. AM is more susceptible to environmental RFI (Radio Frequency Interference)
Repeaters: CB doesn't have repeaters. GMRS is repeater capable to increase range, though typically only around metropolitan areas.
Antenna: For CB the optimum mobile antenna is 108" (1/4 wave), anything shorter is a compromise. For GMRS a 1/4 wave antenna is 6" and needs far less ground plane than a CB antenna so it can be mounted virtually anywhere.

This is an extract from a Jeep Forum ...
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Larry N.

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #9 on: May 15, 2020, 08:20:07 AM »
What Doc says about the comparison is correct, but I'd mention that the AM of CB at short ranges is pretty much as clear sounding as the FM of FMRS, business bands, etc., but with weaker signals the interference can certainly be a problem. As to antenna length, the 108" is correct for CB, as far as it goes, but that's electrical length. Most CB antennas these days (and even in the '60s in its heyday) use various loading coils to get an effective 108" electrically while having physical dimensions no more than a couple of feet, in many cases, for use in magnetic mounts, trunk lip mounts, etc. Still, GMRS is a good way to go if you don't need the potential contact with a broad range of folks (especially truckers) in case of emergency/whatever. And even without repeaters, the range for GMRS should be longer than that for CB in most cases (not all -- radio waves act funny at CB freqs, not talking about skip).

So for your stated purpose the GMRS is probably best. Of course you could do both. ::)

Larry and Mary Ann N.
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2015 Wrangler Sahara Unlimited toad
Formerly: Trailmanor 2720SL, Bounder, Beaver
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95f5334j

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #10 on: May 22, 2020, 04:45:41 PM »
Quote
I nominate channel 15 as the RV channel to monitor ... maybe thereís already one nominated!

I'll start listening to channel 15 while driving, I had already programmed several GMRS frequencies into my 2m/70cm radio in the coach and my HT to use with my GMRS radios when we're at campsites / state parks etc.
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Doc Roads

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Re: GMRS (General Mobile Radio Service) Anyone?
« Reply #11 on: May 24, 2020, 12:30:09 AM »
I use my HT to scan and monitor UHF/VHF too plus GRMS freqs.  Ch 15 is what I monitor too ... itís a common repeater frequency and is used often in my Southern Arizona area.  So Ch 15 is being monitored by at least two RV Forum members!  I suppose that makes it almost official!

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