GMRS vs. FRS

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#1
Sorry, I searched and searched but I could not find an answer to this question. Its probably a basic radio question.

Is there no other difference between FRS and GMRS except the laws surrounding them? Are they effectively the same technology just operating at different frequencies? Or is it that all radio communications are the same, and the only diff between MURS, FRS,GMRS,BRS, xRS is the frequency and maybe laws governing use? But modulation on the frequency is always done with the same technique? Do they always use the same bandwidth, and/or does it matter?

Basically I am trying to grasp what it means for FRS and GMRS to share a channel. Seems like the radio does not really know the difference, except for power level.


Thanks for any info.
 

PeterGV

K1PGV, ScannerCast author
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#2
That's actually a pretty broad question. But I understand that this stuff IS confusing, and manufacturers haven't made it easy.

Both FRS and GMRS are described in Part 95 of the FCC rules. The FCC has a nice page about GMRS and dual-mode GMRS/FRS radios here. The complete rules for part 95 appear here.

Let's make this simple: For the purposes of general two-way voice communications, both GMRS and FRS are "FM radios" -- They communicate using the same sort of technology.

In general (again this is simplified):

FRS channels ALL use narrow bandwidths and only allow a maximum of 1/2 watt of power.

GMRS has two groups of channels: Channels that are shared with FRS and channels that are exclusive to GMRS. For the shared channels: A (licensed) GMRS user can use these shared channels, with narrow bandwidth, and up to 5 watts. On the exclusive channels, GMRS users can use a wider bandwidth and up to 50 watts (fifty, not a typo) of power.

The above ignores a number of differences... such as the fact that repeaters are allowed on GMRS but not FRS, and exactly which emission types and activities are legal on each service. But that's the essence of the difference that probably interest you.

What makes this so damn confusing is that there are lots of radios that have both all the FRS channels and all the GMRS channels. This allows the user to use the FRS frequencies at 1/2 watt... and allows the user to use the GMRS only channels, and the shared GMRS/FRS channels, at higher power but only if they have the appropriate GMRS license.

You can see how people get confused.

Peter
K1PGV
 
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#3
Thank you very much. I believe I have it now. They are all "FM" radios.

Whats the deal with bigger bandwidth? Does it allow clearer sound? FRS and GMRS both use the same bandwidth right? Is there a BW limit specified by law? receiver and transmitter both have to know the BW for it to work?

In the mean time, I'm going to search around and see if I can dig up answers to these questions too.
 

PeterGV

K1PGV, ScannerCast author
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#4
@dnoyeb:

My pleasure. To your follow-up questions...

Whats the deal with bigger bandwidth? Does it allow clearer sound?

Well, basically, yes. But we're talking about VOICE transmissions here, and FM modulation to boot, so either (narrower or wider) bandwidth has plenty of capacity to provide nice, reasonably natural sounding, intelligible, speech.

REALLY whats going on is that the wider bandwidths are the result of older specifications. A historical thing. Over the years, as equipment has become more sophisticated (and able to handle narrower bandwidths), and the demand for radio frequency spectrum space has increased, the FCC has mandated narrower bandwidth. When each channel takes less space, you can have more channels in the same total amount of spectrum. Sort of like narrowing the lanes on a freeway to make room for more cars.

FRS and GMRS both use the same bandwidth right?

FRS and GMRS use pretty much the same bandwidth on the FRS channels. GMRS allows a wider bandwidth on GMRS-only channels.

Is there a BW limit specified by law?

Yes, it's part of the allowed emission designators that are specified for each service.

receiver and transmitter both have to know the BW for it to work?

In general, yes. A transmitter using a narrower bandwidth can be received by a receiver using a wider bandwidth, but the received signal will seem lower in volume.

Hope that helps,

Peter
K1PGV
 
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#5
Thanks a lot!

Very helpful. I'm an Electrical Engineer by degree so I can grasp the concepts you are presenting. I'll probably only hold it in my head a few weeks. But its nice to at least know whats going on while I am making my purchase decision.

Thanks a bunch!
 
Joined
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Messages
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Nashua, NH
#6
That's actually a pretty broad question. But I understand that this stuff IS confusing, and manufacturers haven't made it easy.

Both FRS and GMRS are described in Part 95 of the FCC rules. The FCC has a nice page about GMRS and dual-mode GMRS/FRS radios here. The complete rules for part 95 appear here.

Let's make this simple: For the purposes of general two-way voice communications, both GMRS and FRS are "FM radios" -- They communicate using the same sort of technology.

In general (again this is simplified):

FRS channels ALL use narrow bandwidths and only allow a maximum of 1/2 watt of power.

GMRS has two groups of channels: Channels that are shared with FRS and channels that are exclusive to GMRS. For the shared channels: A (licensed) GMRS user can use these shared channels, with narrow bandwidth, and up to 5 watts. On the exclusive channels, GMRS users can use a wider bandwidth and up to 50 watts (fifty, not a typo) of power.

The above ignores a number of differences... such as the fact that repeaters are allowed on GMRS but not FRS, and exactly which emission types and activities are legal on each service. But that's the essence of the difference that probably interest you.

What makes this so damn confusing is that there are lots of radios that have both all the FRS channels and all the GMRS channels. This allows the user to use the FRS frequencies at 1/2 watt... and allows the user to use the GMRS only channels, and the shared GMRS/FRS channels, at higher power but only if they have the appropriate GMRS license.

You can see how people get confused.

Peter
K1PGV
Peter I agree but I still debate the fact that how many people who bought these radios have also bought the ones for the 22 channels and has now abused the use of them. I do know this for a massive fact that these people abuse the whole 22 channel system. For one example I was doing a scan of all 22 channels in which some kids was fooling around on the emergency channel in which I think is channel 20. I had told them do they have an emergency matter if not, please get off the channel. I do not believe that kids should not be allowed to have them because of their inmature behavior on the radio. Sorry to say but I do not agree that the FCC allowed this abuse on them and not enforce it as they should.
 
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#7
Peter I agree but I still debate the fact that how many people who bought these radios have also bought the ones for the 22 channels and has now abused the use of them. I do know this for a massive fact that these people abuse the whole 22 channel system. For one example I was doing a scan of all 22 channels in which some kids was fooling around on the emergency channel in which I think is channel 20. I had told them do they have an emergency matter if not, please get off the channel. I do not believe that kids should not be allowed to have them because of their inmature behavior on the radio. Sorry to say but I do not agree that the FCC allowed this abuse on them and not enforce it as they should.
The emergency designation for 462.675MHz (channel 20 in the Moto TalkAbout bubble packs) went away when the rules were changed (effective 02/16/1999 IIRC) to allow all-channel licensing where a GMRS licensee can use ALL GMRS primary channels. But I agreee with you in that they shouldn't be fooling around on the radio because they could potentially be hampering communcations pertaining to an actual emergency.

The emergency channel restriction existed back in the days where you picked any TWO of the GMRS primary channels (and the corresponding repeater inputs) and had to have those listed on the GMRS license application. I had to use same old paper Form 574 that your local PD and FD used to apply for their Part 90 licenses. To avoid needing frequency coordination, I licensed myself as mobiles only (no base station) at 50W (GMRS legal limit on the primaries). The license came showing the frequencies plus a note at the bottom saying that GMRS rules were amended back in 1989 and to refer to rule section 95.29 for the additional frequencies. Rule section 95.29 authorized the 7 interstitials (now shared with FRS 1-7) and also allowed the use of 462.675 for emergency and traveler assistance use, if it wasn't already one of your primaries.

Back when I first got GMRS-licensed in 1992, I strategically picked 462.575 and 462.625 as my two primary channels. I went with these two because back then the radio manufacturers had agreed to include these two plus 462.675 for emergency use and the 7 interstitials to make a low-cost 10 channel radio for GMRS. These are the early cheap radios made a couple of years prior to the creation of FRS and the bubble pack radio invasion which followed. The Motorola TalkAbout Distance portables are updated versions of cheap GMRS radios from this era.

My GMRS callsign (KAE9013) even predates the Universal Licensing System (ULS) and resembles an old CB radio callsign.
 
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Smyrna, Tennessee
#8
Sorry, I searched and searched but I could not find an answer to this question. Its probably a basic radio question.

Is there no other difference between FRS and GMRS except the laws surrounding them? Are they effectively the same technology just operating at different frequencies? Or is it that all radio communications are the same, and the only diff between MURS, FRS,GMRS,BRS, xRS is the frequency and maybe laws governing use? But modulation on the frequency is always done with the same technique? Do they always use the same bandwidth, and/or does it matter?

Basically I am trying to grasp what it means for FRS and GMRS to share a channel. Seems like the radio does not really know the difference, except for power level.


Thanks for any info.
Does this mean the radio that have both the FRS and the GMRS channels, that the radio is operating on the 5w power rating when you use the GMRS only channels? Sorry to butt in.
 
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#9
Most of the 'bubblepack' FRS/GMRS radios have no more than 2 watts on the GMRS channels, mainly for reasons of the very limited power supplies they have. 4-5 watts would cause the batteries to die in an hour.

Also, many of them are also sold for the Canadian GMRS market, where the power limit is 2 watts.
 
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#10
Most of the 'bubblepack' FRS/GMRS radios have no more than 2 watts on the GMRS channels, mainly for reasons of the very limited power supplies they have. 4-5 watts would cause the batteries to die in an hour.

Also, many of them are also sold for the Canadian GMRS market, where the power limit is 2 watts.
Well, as least the is much better than 0.5w ! Thank You.
 

Arizona_Scanner

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#15
Not much difference in reality. All frequencies are used by kids to play hide and seek, send call tones to each other, etc. All channels are used on chinese commercial radios to conduct daily business, run school and church operations, etc. I knew of a guy who ran a 45 watt rig with a high gain mast-mounted antenna and had all the GMRS and FRS frequencies programmed for transmit as well as receive. He could talk clearly to bubble packers from many miles around, when he wanted to, as well as use the radio for legit GMRS use. Local businesses here use these frequencies with total impunity, all the time. The Arizona Cardinals had a repeater atop their stadium for a few years using a GMRS frequency, until a GMRS user pointed this out to them. (The FCC did nothing about it after being told).

This band is more of a joke than CB, because at least in CB, everyone KNOWS it is a wasteland. In GMRS / FRS some still pretend it serves some useful purpose. In the era of cell phones, it is silly and the bandwidth should be given to public safety.

As far as actual output, the GXT-600 midland radios have 5 watts listed as an output, and have a fairly decent range of about 1.5 miles on average in the city. FRS cuts that in half. Just FYI.
 

SCPD

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#16
Not much difference in reality. All frequencies are used by kids to play hide and seek, send call tones to each other, etc. All channels are used on chinese commercial radios to conduct daily business, run school and church operations, etc. I knew of a guy who ran a 45 watt rig with a high gain mast-mounted antenna and had all the GMRS and FRS frequencies programmed for transmit as well as receive. He could talk clearly to bubble packers from many miles around, when he wanted to, as well as use the radio for legit GMRS use. Local businesses here use these frequencies with total impunity, all the time. The Arizona Cardinals had a repeater atop their stadium for a few years using a GMRS frequency, until a GMRS user pointed this out to them. (The FCC did nothing about it after being told).

This band is more of a joke than CB, because at least in CB, everyone KNOWS it is a wasteland. In GMRS / FRS some still pretend it serves some useful purpose. In the era of cell phones, it is silly and the bandwidth should be given to public safety.

As far as actual output, the GXT-600 midland radios have 5 watts listed as an output, and have a fairly decent range of about 1.5 miles on average in the city. FRS cuts that in half. Just FYI.
You don't like GMRS you are more than welcome to stay off it,if you do not like licensed users having the frequencies you will get over it.People like you are the reason it is the way it is,ignoring the rules and think you are beyond getting caught,I know a few that have been caught now go troll elsewhere.
 

redneckcellphone

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#17
This band is more of a joke than CB, because at least in CB, everyone KNOWS it is a wasteland. In GMRS / FRS some still pretend it serves some useful purpose. In the era of cell phones, it is silly and the bandwidth should be given to public safety.
what does that have to do with the question?

all aside both frs and gmrs with the same wattage should go the same distance.
 
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#18
what does that have to do with the question?

all aside both frs and gmrs with the same wattage should go the same distance.
Exactly!! Some one asked a question and they should get an answer, not someones bias opinion, and that seems to be happening a lot this site.
 

SCPD

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#19
what does that have to do with the question?

all aside both frs and gmrs with the same wattage should go the same distance.
This some what newbie Arizona_Scanner loves to stir the pot on this topic every given chance so consider him a troll and ignore his ignorance.
 
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