GMRS and CB are virtually identical as far as how they operate on the air, the only difference is one must have a license and pay fees to the FCC in order for legal operation.
As such one can hack ("mod") a standard FRS or CB walkie talkie or handheld transceiver into a powerful multi-user capable radio that will work up to at least 5 miles away from you (provided line of sight) and with excellent audio quality suitable for sending voice messages as if it were an amateur radio station!
This includes repeaters too using simplex frequencies - without any type of ham license!
In fact the only thing stopping this is your imagination.
CB vs GMRS: How do you decide which radio service to use?
Current FCC rules require GMRS licensees to maintain a 1-mile distance from CB radio users, and the reciprocal rule is in place for CB radio operators. But the real question is:
Should there be such distance requirements at all?
What are the operational differences between these two services? [Hint: Other countries don't have the current quarantined rules.]
Reduced power = reduced range.
Though GMRS has increased power, it's still much less than CB.
For example, a typical 10-mile distance on CB radio is equivalent to 200 miles on GMRS– with all other variables being equal. With that in mind, why do people feel the need to stay 1 mile away?
One significant difference between these two services is the presence of repeaters vs linear operation. Naturally linear (non-repeater) operations will have greater restrictions on power and range whereas operations utilizing repeater stations do not share such limitations.
Again, why keep this rule?
Some cite the lack of channels as a reason for needing distance separation between GMRS and CB.
However, many radios imported from other countries support channel spacing as small as 12.5 kHz, that's only 12 channels on a 25 kHz system!
How many do you need?
The GMRS narrow banding rule only allows for 1 watt ERP. Why does this matter to CB? To put it simply, it doesn't! The FCC requires UHF (300-600 MHz) or VHF (144-148 MHz), the radio is just upconverting for use in the license bands they are sold for.
And why require current GMRS licensees to be 1 mile away from CB radios? I see no reason at all! Particularly when we're talking about the Family Radio Service, which is designed to use handheld transceivers at only 0.5 watts!
GNSS/GPS tracking systems are used by both GMRS and CB'ers but again there's nothing in place to prevent them from operating within 1 mile of each other (or even co-located). Those who wish not to interfere will simply avoid the others.
The same goes for APRS radios as well.
ALL rules regarding amateur radio operation should apply equally between these two services.
There should be NO reason why a GMRS licensee cannot construct a linear system within the strictures of Part 95, utilizing ANY power level except 50 watts PEP on SSB/CW OR 25 watts PEP on the phone if desired for 3 or 4 basic reasons:
1) We are talking about non-repeater and point-to-point operation, no contact with ANY other station should be made.
2) GMRS radios can easily run under Part 95 rules (5 watts max on 2M simplex, 12.5 watts max on 222 MHz simplex). No need for more than one watt. The only people confused here are those who don't know that the equipment they use in their "ham radios" shack can easily be used and legally modified for GMRS or FRS GMRS usage. That's a whole different ball game! 😉
3) In case of interference, simply move your radio away from the offending signal until the issue disappears. You will still be able to operate within 1 mile of the CB'er (or any other source of interference) but you will NOT be forced to operate at a low power level nor lose your ability to conduct reasonable conversations!
4) Another reason for requiring GMRS radio licensees to be 1 mile away from CB'ers is because there is potential for eavesdropping on personal conversations.
The current rules require GMRS radio users to remain "at least 1 mile" from any CB receiver.
However, if you do not have a crystal-controlled transceiver or properly installed filters, anyone within close proximity may monitor your communications.
This can apply even in situations where no conversation is taking place; someone could listen to the sound of buttons being pressed and deduce information about the user's location or activities, which is a safety concern.
These same rules MUST apply equally to both GMRS and CB, there should be no separation requirements put in place for GMRS licensees with respect to CB!
If I'm within 1 mile of another ham or CB'er then that's my business NOT the FCC nor anyone else.
What does GMRS Stand For?
"General Mobile Radio Service" - it's a personal radio service in the United States, designed for short-distance two-way communication. GMRS is similar to FRS but with much more power (up to 50 watts) and four times as many channels (16 for GMRS vs. 4 for FRS).
It is available to all individuals who are at least 18 years of age or older. GMRS does not require a license, although one must register their callsign with the Federal Communications Commission (FCC).
Any individual may operate an unlicensed Part 95 device on any frequency so long as they do not cause harmful interference .
Some facts about "GMRS":
1) Max output: 50 watts PEP, 12.5 watts carrier power on 462 MHz or 50 mW max (0 dBm) on GMRS frequencies .
2) Qualifications: Must be at least 18 years old and a US resident. A license is not required, but you MUST register your callsign with the FCC.
This is also a "dual service" meaning that it operates under both Part 90 for commercial mobile use and part 95 , which enables anyone to use GMRS without any type of government permission!
On the PROS and CONS :
Uses UHF for local comms only, not HF nor V/UHF - no need for repeaters . Typical range 1-3 mile range with handheld transceivers, 5-10 miles with a base transceiver and proper antenna. GMRS operates in two bands: 462.5525 - 467.7125 MHz and 467.7375-472.7875 MHz.
In the latter band, channels have been further divided by region into 25 kHz increments to prevent cross-frequency interference between adjacent contiguous channels; for example, channel 1 is 468.250 MHz everywhere but on the west coast where it's 468.275 MHz.
This has no effect on local communications as any transmitter (including walkie-talkies) will only transmit within a given 20 kHz wide segment of frequencies selected by the user. Channels 1-14 are primary allocations, 15-21 are secondary allocations.
What is a CB?
Citizens Band, or CB for short, is a UHF (Ultra High Frequency) radio service intended for personal or business use. This service operates in the 27 MHz band . Channels number 1-40 are primary channel assignments and channels 41-80 are secondary .
The maximum output power of a CB is 4 watts on AM mode or 12 watts PEP on SSB CDMA mode , all other modes are limited to 2 watts transmit power except FSK which has no limits and CW which has 3 watts max .
IMPORTANT: Even though 40 channels are listed below as "Primary", they are not necessarily continuously available worldwide!
-You may like: How to Fix a CB Microphone Wiring
Some countries have added extra channels not shown below while others may have removed some: The USA for example has added channels 14A-14J (17.235 MHz) and D (26.965 MHz) .
Think about that for a minute, the most popular communication bands in amateur radio are EME/moonbounce on 2m/70cm, 160m and 80m.
The whole HF spectrum is available to us but what's the point of operating there when the band is crowded with QRM from other services?
We're forced to sit out some weekends due to propagation conditions or we have no alternate place other than VHF/UHF for local communications because of overcrowding on HF!
It took them 30+ years to get rid of Part 15 rules on 2 meters and only 50 watts maximum power? It's going to take them more than 30 years if they ever decide to do it again!
Even though 462MHz is not a perfect band for all purposes, at least there is no QRM and less congestion on the local repeaters.
Let's face the facts:
When you're limited with 50 watts or less why bother operating on HF at all? If propagation isn't good then forget about HF operation altogether and stick to 2m/70cm until conditions improve.
Try using simplex mode (radio-to-radio) in your area as often as possible instead of linking up through repeaters due to congestion.
CB vs GMRS: Why choose CB over GMRS?
Think about this - you don't have to worry about managing the duty cycle and retuning your radio because of band plan restrictions on CB.
If you're using a handheld transceiver then there's no need for high power output or external antennas! When it comes to local comms why would you want anything more than what you can get with CB?
On the other hand, think about all the fun activities that GMRS offers:
1) Public service communication: Disaster communications, Organized events (organize a convoy!), Search & Rescue, Emergency response teams, and Government coordination. This is only possible under Part 95 as anyone can use GMRS without any type of government permission.
2) Radio control by hobbyists: Vehicle-mounted mobile stations operating under Part 95 can be used for model control. CB is not allowed to do this due to a lack of frequencies to use.
3) Radio control by ham operators: Ham radio operators have the option to operate within Part 97 on 2m/70cm, a band primarily designated for FM simplex operation but is also shared with GMRS repeaters.
You might like: What's the Difference between a Ham Radio & a CB Radio?
This means we can communicate between our remote-controlled models via voice using repeaters (i.e. radio control from our house or base station).
We could even talk directly with other hams listening on the same repeater if they were in the area, perhaps coordinating activities such as launching into a local flying field, etc - something that's very difficult and impractical when attempting direct-by-voice communication between mobile stations on GMRS!
If your only goal is to have a ham radio shack as an addition to your house or to simply operate as many radios as possible then CB is better than GMRS.
But if you want to use it for purposes that go beyond just local comms and voice operations then, by all means, choose GMRS.
However, GMRS offers much more than just voice communications! (hint: Better sound quality)
Propagation: CB is of poorer quality than GMRS when it comes to propagation. This is because 2m band frequencies are higher up in the VHF spectrum which means they're harder to refract, reflect and scatter.
Higher frequencies from 70cm may be able to bounce off of buildings for example.
However, this doesn't mean that you cannot use 2m/70cm for long-distance communication but it's simply not as good as using HF because you can hear more stutters and QSB on your signal.
If your repeater is located more than 50 miles away then there's a high probability that due to terrain effects, other signals will fade out before yours even reaches halfway across the country at best reception.
The chances of hearing your signal diminish the further away from you it travels.
This is why even though CB and GMRS are both line-of-sight, the range on 2m/70cm is not as great as HF where a signal can be heard for hundreds or thousands of miles.
GMRS channels are wider than CB but shorter in range due to license class restrictions. WA5WAA's channel plan comparison shows that GMRS channels are 1.5 times wider than CB while having half of the output power per sideband...but this doesn't tell us how much bandwidth we have available on either system because he didn't compare them directly using each other's terms.
If we do this then it shows that 2m/70cm offers only around 36% of the bandwidth available on 144MHz in the same portion of the spectrum.
Repeater output power: The maximum ERP (effective radiated power) is higher on GMRS channels due to Part 95 license class restrictions.
This means that you have a much better chance of being heard over long distances and can even go longer without needing a repeater to relay your signal further away! Click for more info on DMR-MARC Repeaters - though be aware that those are not legal for ham radio to use, they're just here as examples.
GMRS provides international access: In general, GMRS frequencies are also used in other countries too and not just the USA.
This means that we can access these channels, albeit with a slight shift in frequency, when traveling to other countries where GMRS is also used (i.e. Canada).
However, as mentioned previously it's only Part 90 licensees who have access to 902-928MHz frequencies including that above 915MHz so they may not be accessible from abroad.
GMRS supports time division duplexing: Time Division Duplexing (TDD) allows one simplex channel to be shared between the two users by alternating transmissions - see how this works here.
TDD is considered very useful for low-duty cycle activities such as flying model aircraft since it frees up some of the airtime for those who are not speaking. TDD is done by creating two repeaters, one on transmit and one on receive only.
Time Division Multiple Access (TDMA): Time Division multiple access allows more than 2 users to share a single talking channel in order to reduce airtime requirements.
This is allowed via Part 95 subpart T - but this doesn't apply solely to GMRS operators but also Family Radio Service (FRS). There are various modes that can be used with or without encryption and they all vary between different manufacturers.