GMRS Radio

Dino - KX6D

Radio Guy
Supporting Member
Joined
Jan 29, 2017
Messages
258
Location
La Mirada, CA, United States
GMRS (General Mobile Radio Service) Radio is becoming very popular with off-road enthusiasts thanks to a few "influencers" and Midland. GMRS is basically a throw back to the the days of licensed CB radio which was intended for the general pubic. However GMRS uses UHF frequencies (467MHz) rather than HF (27MHz) and FM (frequency modulation) rather than AM (amplitude modulation). What sounds better, your FM stations in the car or the AM? Clearly FM is the winner! GMRS is a LICENSED service and therefore you need to buy a license, but it does NOT require a test like ham radio does.

The other advantage to GMRS radio is the higher frequencies. The higher the frequency, the shorter the antenna. While a 1/4 wave antenna for CB is 9' (remember those long stainless steel whips?), a 1/4 wave antenna for GMRS is 6". You can mount a GMRS antenna almost anywhere and barely know its there!

GMRS also gives you the ability to use "repeaters" which simply stated are nothing more than a receiver and a transmitter tied together on a mountain top to increase your broadcast range. Just as standing on top of a mountain lets you see farther, a mountain top repeater also allows your radio signal to travel farther. The receiver picks up your transmission on frequency A and sends it to the transmitter that sends it out frequency B at that exact same time, as if you were actually standing on top of that mountain. When your radio is in repeater mode it LISTENS to frequency B, but when you push the button it automatically switches to frequency A, then switches back to B when you let go of the button. This is called DUPLEX. If you want to know more about repeaters, let me know.

If there is any disadvantage to GMRS its that its only "line-of-sight" transmission. In other words, if you can't SEE it, you can't talk to it. Wheeling in groups is rarely a problem but its important to point out that if the rest of the group is on another side of a hill, they may not be able to hear you until you get back in sight with them. VHF and HF frequencies are a little more forgiving in this respect. However, the good outweighs this one minor drawback.

You can increase your range by using a radio that puts out more power, like a mobile radio permanently installed in your Jeep. You can also increase your range by running a 1/2 wave or 5/8 wave antenna which gives you more "gain". Its like turning up the volume on your stereo. But a simple inexpensive handheld radio will work 90% of the time.

If you are committed to GMRS radio, do yourself a favor and buy a mobile radio and install an antenna on your Jeep! All you really need is a 1/4 wave antenna that's only 6" high. it will need a ground plane of sorts so mount it to the hood, cowling, or fender while trying to keep it away from any other metal. I've seen them mounted INSIDE the Jeep in the back on the rail the hardtop sits on and it works great. If you want the best of the best, you mount it on the roof or top of the roll bar if you don't run a top. if you want to install it on the fiberglass hard top, you can buy a 1/2 wave antenna (12" long or so) that requires no ground plane.

I just bought two UHF 1/2 Wave NGP antennas from Rugged Radios that are on clearance for $24.00 to experiment with. They will be mounted INSIDE my Jeep in the rear.

When I wheel, most everyone is on VHF and I like it better. But with the surge towards GMRS in the UHF band, its important that we get the right information out to people who want to make that move from CB. If you have questions, let me know.
 
I’ve been thinking about getting a midland MXT-115. Was considering getting an antenna mount that goes on the side of the base of the drivers side windshield, just in front of the door mirror. Not sure if I’d want to use their little stubby 3 db gain antenna or the 32” 6 db gain antenna.

Would that be a good location for the antenna?

Also, theres no timing a GMRS antenna like a cb antenna, correct?
 
Now that I have a license and a radio is there anything specific that I need/should do when using it, as opposed to a CB?

Do I need to identify myself by my call sign?
 
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I’ve been thinking about getting a midland MXT-115. Was considering getting an antenna mount that goes on the side of the base of the drivers side windshield, just in front of the door mirror. Not sure if I’d want to use their little stubby 3 db gain antenna or the 32” 6 db gain antenna.

Would that be a good location for the antenna?

Also, theres no timing a GMRS antenna like a cb antenna, correct?
I have mine on the front left window hinge. Its not ideal because of the window frame. The CB antenna is on the rear driver's side which isn't ideal because of the roll bar just inside the hard top. Neither are ideal but its what I had to work with and they work! Everything works, some things work better! 3.73 gears and 35's work, but 5.38's...

You want the antenna clear from other metal objects. Center of the hood is great, just not practical. Fender works but the hood is in close proximity. Its a battle! I see a lot of antennas that use a flat bar coming from between the hood and the fender. This works too. If you have a lightbar, mount it up there! I didn't give you a clear answer because there isn't one, but I hope this helps you understand.

As for tuning, all antennas need tuning. At the very least checked! The UHF antennas cover a wider range because of the size of the wavelength. CB is measured in feet and UHF in millimeters so it may be fine right out of the box. I always check but you have to have the right meter that can handle UHF frequencies.
 
I’ve been thinking about getting a midland MXT-115. Was considering getting an antenna mount that goes on the side of the base of the drivers side windshield, just in front of the door mirror. Not sure if I’d want to use their little stubby 3 db gain antenna or the 32” 6 db gain antenna.

Would that be a good location for the antenna?

Also, theres no timing a GMRS antenna like a cb antenna, correct?
This is a great Micro Mobile radio. That stubby antenna is the real deal.

What do you mean with timing?
 
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Now that I have a license and a radio is there anything specific that I need/should do when using it, as opposed to a CB?

Do I need to identify myself by my calm sign?
Excellent question! I don't know what the identification requirements are for GMRS so I'll look it up and "edit" this message!

YEP!!! (Click the link!)
 
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Excellent question! I don't know what the identification requirements are for GMRS so I'll look it up and "edit" this message!
Look under the 47CFR 95.1751. It should be after every 15 minutes of transmisión or at least every 15 minutes. We mostly does it at the end of the transmisión because we keep it shorter than that. Trail rides, you know how it goes.
 
GMRS (General Mobile Radio Service) Radio is becoming very popular with off-road enthusiasts thanks to a few "influencers" and Midland. GMRS is basically a throw back to the the days of licensed CB radio which was intended for the general pubic. However GMRS uses UHF frequencies (467MHz) rather than HF (27MHz) and FM (frequency modulation) rather than AM (amplitude modulation). What sounds better, your FM stations in the car or the AM? Clearly FM is the winner! GMRS is a LICENSED service and therefore you need to buy a license, but it does NOT require a test like ham radio does.

The other advantage to GMRS radio is the higher frequencies. The higher the frequency, the shorter the antenna. While a 1/4 wave antenna for CB is 9' (remember those long stainless steel whips?), a 1/4 wave antenna for GMRS is 6". You can mount a GMRS antenna almost anywhere and barely know its there!

GMRS also gives you the ability to use "repeaters" which simply stated are nothing more than a receiver and a transmitter tied together on a mountain top to increase your broadcast range. Just as standing on top of a mountain lets you see farther, a mountain top repeater also allows your radio signal to travel farther. The receiver picks up your transmission on frequency A and sends it to the transmitter that sends it out frequency B at that exact same time, as if you were actually standing on top of that mountain. When your radio is in repeater mode it LISTENS to frequency B, but when you push the button it automatically switches to frequency A, then switches back to B when you let go of the button. This is called DUPLEX. If you want to know more about repeaters, let me know.

If there is any disadvantage to GMRS its that its only "line-of-sight" transmission. In other words, if you can't SEE it, you can't talk to it. Wheeling in groups is rarely a problem but its important to point out that if the rest of the group is on another side of a hill, they may not be able to hear you until you get back in sight with them. VHF and HF frequencies are a little more forgiving in this respect. However, the good outweighs this one minor drawback.

You can increase your range by using a radio that puts out more power, like a mobile radio permanently installed in your Jeep. You can also increase your range by running a 1/2 wave or 5/8 wave antenna which gives you more "gain". Its like turning up the volume on your stereo. But a simple inexpensive handheld radio will work 90% of the time.

If you are committed to GMRS radio, do yourself a favor and buy a mobile radio and install an antenna on your Jeep! All you really need is a 1/4 wave antenna that's only 6" high. it will need a ground plane of sorts so mount it to the hood, cowling, or fender while trying to keep it away from any other metal. I've seen them mounted INSIDE the Jeep in the back on the rail the hardtop sits on and it works great. If you want the best of the best, you mount it on the roof or top of the roll bar if you don't run a top. if you want to install it on the fiberglass hard top, you can buy a 1/2 wave antenna (12" long or so) that requires no ground plane.

I just bought two UHF 1/2 Wave NGP antennas from Rugged Radios that are on clearance for $24.00 to experiment with. They will be mounted INSIDE my Jeep in the rear.

When I wheel, most everyone is on VHF and I like it better. But with the surge towards GMRS in the UHF band, its important that we get the right information out to people who want to make that move from CB. If you have questions, let me know.
Excellent!

I I like to add that they GMRS license fee was dropped to $30, if no recall wrong is already active. Also, the license covers you and the immediate family. Each radio should Identify using their call sign - 1 or 2 or....

WRJE690
 
Also, theres no timing a GMRS antenna like a cb antenna, correct?

Depend on the antenna type pre tuned but the nice ones need to be tuned. The process is similar just different SWR meter.
For the antennas that have adjusters, yes - you can and should tune them. The SWR meter is just different. I bought an SW-33 to do mine soon.

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I made the switch a few months ago. Ditched the CB and Firestick for a Midland MXT-275 and their 6db gain antenna. Bought the license and mounted the antenna on the tail light mount. Not an ideal location, but I didn't want it on the hood or cowl. I also picked up a Browning BR-450 antenna just to see if I could get a better SWR. The Midland antenna gave me the best SWR out of the two, so I'll be bringing the spare Browning antenna as a spare. I also got the SW-33 meter to tune them. Best I can get with the antenna where it is is 1.43:1. It's a compromise, but good enough. We have several repeaters in my area and am amazed at the range I can reach with them. You can go to mygmrs.com to get a map of available repeaters. Some you need to get permission from the owner to use them, or get the appropriate PL tones. I also picked up a HT from Radioddity for $39. It's 5 watts and pretty simple to use, and it's part 95E compliant for GMRS, unlike the evil UV-5R, lol!

To answer the question about antenna tuning, you can tune them for a better SWR, but you don't need to take much off. Most you only need to snip a half inch or so shorter. Do it in very small increments with wire cutters, or a saw. Go too short and you throw it away.
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