GMRS (General Mobile Radio Service) Thread

https://www.breedlovemounts.com/ezn-stake-pocket-bracket.html

I dont have one of these , but they look like quality parts.
I have the Midland antenna and it works very well.
I know you can buy parts to make your own antenna of Amazon for about $20

 

Unfortunately my tonneau cover rails cover the stake pockets, but I could make a mount that extends past the rail. Of course higher mounting is better.

 

I see people with firestick antennas for their cb. For they work with a GMRS radio?

 

You will need to ensure it is tuned to 450-470 MHz range. That is the GMRS range. I do not know if firestik makes one for GMRS.

 

Ok. Yes, I've been in a crash course all week reading about this. Thanks!

 

No CB won't work. The range for CB is 26.9650 MHz to 27.4050 MHz.

 

I use the Diamond K400C mount. Can put that in many location, and super strong. Note, depending on your antenna make sure you get the right mount with NMO or UHF connector! BTW the below picture is with the Comet CA-2x4SR antenna, which is 40 inches tall. You get the idea. Note, you need a ground plan to have your antenna work well, i.e. a piece of flat metal (like the hood, or roof) electrically connected to the ground of the antenna.

 

No. Totally different frequencies for CB vs GMRS. 27 MHz vs 462 MHz. Antennas need to be tuned to the desired frequencies to operate. Multi-band antennas exist, but I've never seen them for CB and GMRS in one. Even if they do exist, a firestick is not a multi-band antenna.

 

I'd like to use my bed rail system to mount an antenna. If I use the Midland 6db antenna, what would I need to use to connect this? Just a bracket, cable and antenna? I'm reading a lot of forums that have info on this, but it's taking a lot of time to piece it together. NMO, ground plain, decibels, MHz. Don't get me wrong, I find all of this very interesting and I once I'm interested, I'm like a dog on a bone.

So as far as the antenna being grounded, will this work?

And as far as the cable running from the radio to antenna, I read it's important to have quality. Any recommendations on this?

 

What you need is an antenna bracket, coax cable to the bracket from the radio, and of course an antenna. An in-line noise filer on the 12V to the radio is not a bad idea either, so that no alternator whine gets transmitted on your signal. If you're not comfortable attaching your own coax cable connectors to a piece of coax cable, try to find a mount that comes with it pre-assembled. As for quality of the coax cable. Coax cable has loss, meaning some of your signal gets dissipated in the coax instead of going out of the antenna. Loss is a function of frequency and length. The higher the frequency, the more the loss per foot of cable. Now, since this is a car, you will run maybe 10 feet of cable, and in that case you can pretty much ignore the loss in the coax. Here's a chart of various different coax cable types and their loss per 100 foot.

http://rfelektronik.se/manuals/Datasheets/Coaxial_Cable_Attenuation_Chart.pdf

The Diamond K400C antenna mount I mentioned earlier uses RG316, at 400 MHz that is 16.7 dB per 100 foot loss. So at 6.5 foot (the length the mount comes with) that is only 1.1 dB loss. So nothing much to worry about. RG316 is super thin, and therefore pretty lossy. General rule of thumb. The thicker the coax, the less loss (more or less). Now, do keep your coax cable as short as possible. Don't get 50 feet and coil up 40 feet of it.

Make SURE the antenna mount is connected to the frame of the truck/bed, somehow. You might have to sand off some paint right where the mount goes to make that happen.

If you want to make sure your antenna system is working once you've installed it, get (or borrow) a SWR meter. If you get to a SWR of less than 2.0 at the GMRS frequencies (462.something MHz) you've done well.

Good luck!

 

Wow! That was a big help. Just what I needed to be confident in what I'm spending my money on. Thank you

 

Bed rail option? https://www.relentlessfabrication.com/products/05-tacoma-bed-rail-mount-tab

 

Is your RADIO legal to use on GMRS?

Certifications can change over time and the ONLY way to know is to check the FCC ID on your radio.
Here is a link to the FCC certificate search:
https://www.fcc.gov/oet/ea/fccid

 

I saw that. Very nice, but I think I'm going to save myself a little money and just make one myself.

 

No problem! If you're building your own coax cable, be sure to get 50 Ohm cable, not 75 Ohm TV cable. At least, I expect the Midland GMRS radios to be 50 Ohm output.

 

If mounting a GMRS antenna on the bedrail on the rail just behind the cab on the left side, does that constitute a large dB loss due to location? I am debating the middle of the roof for grounplane issues or a mount like that one in the link with a taller antenna. F you science.

 

Mounting on the bed rail at any location will have a drastic effect on the transmission pattern. Placing it low will also cause transmitted energy to be absorbed by the higher truck cab creating an irregular ground plane and transmission pattern and why center roof placement provides optimal performance. A good magnet mount antenna placed on cab roof will provide optimal performance in place of a permanently mounted antenna as a best option.

 

Yup, the roof is always the best choice. Only reason I didn't do that is due to the antenna height hitting branches, etc, when offroading.

 

Well my MXT275 will be here tomorrow. I will work to get it mounted in the center console while I wait for the NMO mount to get delivered.

I was going to mount on the front fender, but after some research and the helpful image above I think I will try my hand at a roof mount. I remember seeing a full install on another forum I think. It doesn't look too hard just have to make sure to measure 3 times before any drilling.

Right now I am looking at this

$27 Larsen - 3/4" Hole Mount Antenna with 0-6 GHz Frequency No Connector

Larsen Mount and these

RFIOTASY Pack of 5 UHF PL-259 PL259 Male-Plug Crimp Coax Connector Adapter RF Connector for RG58/U LMR195 Coax Cable Compatiable with Ham Radio (UHF Male Crimp RG58)

PL-259 ends. I will probably drive around with

$23 Browning BR2445 450MHZ–465MHz Pretuned Low-Profile UHF Band NMO Antenna, 3 1/4" Tall

this antenna so I can make it into the garage without issue and swap out to

$32 Tram 1180 Amateur Dual-Band NMO 38" Antenna VHF 144-148 and UHF 430-450 MHz for Mobile Radios

this antenna that I already have from my scanner. I'm open to suggestions for antennas that may perform better when longer range is needed.

 

@P-Factor, Thank you for that schematic. I will probably do the roof mount also just for peace of mind and because P-Factor has that recipe already. Kind of like the 6112 Bilstein/5160 rear suspension setup. It is proven on Tundras and it works and several others have proven it.

If anyone could find that roof top installation link, that would be awesome for this thread. Or P-Factor can drop a knowledge bomb also.

 

Before you drill, make sure that you have routing of your coax planned. It took me several weeks of probing and planing for careful routing due to Tundra's many Air Bags and not causing air bag interference.

 

As for the Tram Antenna, that is a HAM dual-band, meaning it is tuned for 430-450 MHz. At GMRS frequencies it likely will have high SWR. You might be able to adjust that by shortening the antenna rods a little bit, if you have a good SWR meter available. Another thing to consider, since it also supports the VHF band, it will have to be longer than a dedicated GMRS antenna with the same gain. So if you're worried about height, consider that as well.

 

@Zero One Actual Found the thread that I was mentioning before. Looks like photo bucket was nice enough to blur his photos. I'll reach out to the user to see if I can get a copy. Looks like a pretty decent guide. https://www.tundratalk.net/forums/t...1-ham-radio-installations-13.html#post7099170

 

Most antenna manufactures provide a trimming chart as exampled below:

Edit: Several attempts to rotate image have failed. Please accept my apology.

 

The following is a decent video regarding installation of a NMO mount:
https://www.youtube.com/watch?v=LBEVwzo53J8

 

Drilling the hole:
After gathering my thoughts which included a final Big Sigh... I prepared the area to be drilled by applying a layer of blue painters tape for the purpose of eliminating/minimizing scratching and/or drill crawl. I then used a DeWalt Mod. D180012IR 3/4" holesaw attached to a DeWalt impact driver. All went well and without any mishaps and a clean job. Very Important and particular to white truck owners! Gently, (to prevent scratching) but thoroughly, clean off all metal shavings and/or particles otherwise they will rust and stain your paint! I used an air hose as my first step while being careful not to blow fragments onto other parts of the truck and when finished, I washed my truck as normal looking carefully for any missed particles.

 

So in theory, what if I took the Rago/ Relentless Fabrication bed rail mount and installed your same antenna right in the middle of the bed rail that is directly under the rear window? We all have the bed rail that goes perpendicular to the truck right under the back window. Would the antenna being higher than the roof catch any ground plane or no? Just shut up and drill?

 

Think of a ground plane as the electrical equivalent of a mirror under your antenna making your antenna longer, so your signal comes out more efficiently. You need enough metal under the antenna to make that work optimally, probably at least 1/4 wavelength radius. So about 7 inches radius circle. If I were you, I would NOT go with the antenna I have, unless you want to also transmit on HAM frequencies. As it is unnecessary long for GMRS work. As shown above by P-factor, any mounting location other than on the roof is a compromise in how well your signal goes out. You need to decide what works best for you location wise. Now of course, where you want to put it will work just fine, you just give up some efficiency. In the end will it matter in terms of range? Hard to say, maybe you can get another bit of range if you had mounted it on the roof and can talk to that person right at the limit. But many other factors (buildings, trees, weather, cars next to you, etc) also affect range. In the end, a simplex communication over GMRS will be limited by line of sight and what blocks the signal between the two talking parties. It will never be as good as talking over a repeater on top of a mountain or on top of a tall building.

What I do know definitely sucks is using a handheld inside the cab, with a rubber ducky antenna. That is a recipe for very poor signal propagation. So your plans are a huge improvement already!

What you also can do is to buy a mag-mount antenna mount first, and try it out. Put it on the roof for a while, put it on the rail for a while, and just experiment. Run the coax between the window and weather stripping, so no permanent install needed. Once you get a feeling for these locations, then decide.

 

Agree.

 

I assume mounting

I also agree with this. One thought if you really don't want to drill you could mount a single ladder rack near the rear window/front bed and mount an NMO to that and either use an antenna with a ground plane (4 posts sticking out like

$39 Tram 1465 Land Mobile Base Ground Plane Kit

this or a circular ground plane like this. You would also need a good ground to the mount. I'll let some of the more seasoned members weigh in. Ultimately you want to be high or higher than roof with a good ground plane to get the best performance.