GMRS vs 900mhz

[K9RNW]

Hi all,

I was wondering what would be better for car-to-car and car-to-base communication, GMRS or the 900mhz "DTR" type radios. I have heard that the 900mhz band has better range than GMRS with respect to handhelds, however I have not seen any high power 900mhz mobile units.

I am not sure either is "optimal" for a hilly, suburban environment, however I am inclined to believe a 45W GMRS mobile would transmit much farther than a 1-2 watt DTR handheld. Is my presumption correct?

Any insight is welcome

 

[K4DPA]

Overall your best choice would be GMRS (460 MHz) vs higher frequencies like 900 MHz. Higher frequencies like 900 MHz have a shorter wavelength allowing smaller antennas like ones on portables to work better. However, these small radio waves are not able to travel around objects like terrain and buildings like bigger radio waves can. UHF works best in cities and metro areas with buildings. VHF works best in rural and hilly areas. Since your comparing GMRS vs 900 MHz, the GMRS would be the best option.


- Dawson Adams
K4DPA / WQPN413

 

[NC1]

Generally, the rule of thumb is that the higher the frequency, the worse it is going to perform in hilly terrain that is rural or sparsely suburban. If you have to decide between the two, then GMRS is the answer.

I am in a very rural area with lots of hills, mountains, and lots of forest. Around here I see a lot of VHF High (analog) use by almost all the local Police, Fire, and Ambulance. They are set up like that for good reason: it works the best of all their options given this terrain.

There is a multitude of CB use around here (more than anywhere else I have ever lived), and I hear the average Joe using all 5 of the MURS channels on an almost daily basis. The VHF (144MHz) repeaters are in heavy use in the area, followed by the UHF (440 MHz) repeaters.

GMRS transmits on 467.xxx, and receives on 462.xxx, so that is probably the upper limit you want to go in rural and hilly terrain. Hope that helps.

 

[nd5y]

however I have not seen any high power 900mhz mobile units.

Unless you have an amateur radio license it would not be legal to use radios that exceed Part 15 power limits in the 902-928 MHz band. As far as I know hams that use that band are all using modified commercial radios.

 

[K9RNW]

Thank you all.

My environment is slightly hilly and suburban. What range do you think would be possible with a 40-50W GMRS mobile?

One thing I would like to be able to do is have the range to reach out to another family member's household which is about 17 miles away as the crow flies. I have no idea if a mobile radio connected to a 1/2 wave antenna on a second-floor desk would be able to do that, but if I can get away with not having to install base station antennas in our attics....

 

[mmckenna]

Hi all,

I was wondering what would be better for car-to-car and car-to-base communication, GMRS or the 900mhz "DTR" type radios. I have heard that the 900mhz band has better range than GMRS with respect to handhelds, however I have not seen any high power 900mhz mobile units.

I am not sure either is "optimal" for a hilly, suburban environment, however I am inclined to believe a 45W GMRS mobile would transmit much farther than a 1-2 watt DTR handheld. Is my presumption correct?

Any insight is welcome

For car to car and car to base, a UHF radio with an externally mounted antenna is going to work well.
While 900MHz can perform well, coaxial losses will be more pronounced on the higher frequencies if you are running an external antenna. With 1 watt and 15 feet of RG-58, you'll get a bit over 1/2 a watt to the antenna. With a 45 watt UHF radio, you'll get about 30 watts to the antenna. Usually RF power doesn't make as big a difference as people think, but 1/2 watt versus 30 watts is enough to be worth it.
On the antenna side, a high gain 900MHz antenna is going to be smaller than a similar gain UHF antenna, which might be an advantage on some installs, but higher gain in hilly terrain might not work as well.
And don't forget about losses on the other end, base or mobile.

With an FCC issues GMRS license and a Part 95 certified radio as well as a proper external antenna, GMRS is going to work better. For years I ran 35 watt UHF mobiles with family. On flat terrain it was pretty easy to get 15 miles of range between vehicles. Add in the availability of GMRS repeaters as well as being able to add 70cm frequencies to a commercial radio, and it's likely a better investment.

 

[mmckenna]

Thank you all.

My environment is slightly hilly and suburban. What range do you think would be possible with a 40-50W GMRS mobile?

One thing I would like to be able to do is have the range to reach out to another family member's household which is about 17 miles away as the crow flies. I have no idea if a mobile radio connected to a 1/2 wave antenna on a second-floor desk would be able to do that, but if I can get away with not having to install base station antennas in our attics....

A 1/2 wave antenna without a ground plane is going to have zero gain. Inside a house with people, wiring, local noise sources, etc, you are going to have issues. External antenna mounted up high is the way to go.

Local terrain is going to play a big part in your coverage. UHF is line of sight.

 

[scma127]

Overall your best choice would be GMRS (460 MHz) vs higher frequencies like 900 MHz. Higher frequencies like 900 MHz have a shorter wavelength allowing smaller antennas like ones on portables to work better. However, these small radio waves are not able to travel around objects like terrain and buildings like bigger radio waves can. UHF works best in cities and metro areas with buildings. VHF works best in rural and hilly areas. Since your comparing GMRS vs 900 MHz, the GMRS would be the best option.


- Dawson Adams
K4DPA / WQPN413

i love 900 mhz even though i have gmrs how did you put your call sign below i want to ad mine where do you go ty

 

[K9RNW]

A 1/2 wave antenna without a ground plane is going to have zero gain. Inside a house with people, wiring, local noise sources, etc, you are going to have issues. External antenna mounted up high is the way to go.

Local terrain is going to play a big part in your coverage. UHF is line of sight.

You're right. What I should have said is a 5/8 wave...I only plan on using 1/2 waves for vehicle roof magmounts.

Would that do it, or would I still need a large base station antenna to get out 17 miles?

 

[kb5udf]

range

For RELIABLE (empahsis) comunications for than a few (2-5) miles, some type of high base antenna is usually required. Reason being line of sight distance for typical mobile to mobile antennas is not much more than 5 miles or so. Even then, terrian and/or foliage can further reduce range from that. You won't always get line of sight ideal range, but in some instances you can get better, but you should not count on it.

Google the various uhf/vhf of sight range calculators as a rough guide. Again, if you have alot of foliage or hills, the actual range will be less than predicted.

Regards

JB

 

[N4KVE]

Here’s a perfect apple to apples comparison. Years ago I’d drive up the highway following my wife. We’d talk car to car using 2 900 MHz MTS2000’s. Rubber duck on both radios. 3/4 mile max range. So the next trip I used 2 UHF MTS2000’s, also rubber ducks. This time max range was 1 mile. However on a cruise ship, we use 900 MHz radios, as the higher freq will have better penetration for the ship.

 

[alcahuete]

As has been mentioned, GMRS is likely your best option here. That said, I have taken my 1w (890mw actually) DTRs out to 23 miles here in the desert...of course line-of-sight with minimal obstructions in between. I actually ran out of road, which is why I didn't go farther. They out-perform my 4w UHF and GMRS stuff any day of the week out here.

In your situation though, hilly, suburban area, I would assume that UHF is going to perform better.

 

[PACNWDude]

+1 on others that say GMRS will be longer range for your use.

I am also in a mountainous area with lots of pine trees and 900MHz DTR radios get about one mile maximum. This is what they were designed for, one watt output and up to a mile range and able to penetrate buildings and ship decks.

If you get non DTR 900 MHz radios, make sure you are not using them near any cell phone bi-directional amplifiers. I had some local Coast Guard members wondering why they had no cell phone reception in a remote area, and they had burned theirs out by overpowering them with their handheld radios.

For forest and pine trees with hills and mountains, UHF and mobile radio will work better than handhelds at lower power.

I use Vertex VX-3200 UHF for car to car use, have them set slightly lower than factory at about 35 watts output and Antennex Phantom style antennas, and get about 9-12 miles pretty often.

In comparison, Kenwood TK-941 mobiles at less power and higher frequency only get about 3-6 miles, but work better when in the city with more concrete structures than pine trees around.

VHF works the best for both, and a Vertex VX-3200 in VHF tuned for about 45 watts often get me 13-15 miles range, unless I am in a deep valley when mobile. All of my use is not over a repeater, this is Line of Sight, simplex.