Ham Radio Install
& GMRS Relocation
Reprised from previously. GMRS radio on "Hooke Road" mounting plate.
New Retevis RT-95 Ham radio.
Radio mounting bar from "Arizona Rocky Road".
Wiring, grommet, and center hole were provided. I added the two outboard holes to route coax through.
Retevis Ham, and relocated Midland GMRS, radios.
Programming the Retevis.
Head-on view. Uploading config to the Retevis.
Coax junctions for both the Retevis (Ham) and Midland GMRS. Note removed radio mount.
Said mount now in its new owner's Jeep. If I'd known he was
going to use it for a smartphone, I would have charged him more!
This was where I had the little GMRS antenna located. VSWR of 2.5.
This is where it ended up. VSWR of 1.5.
Figured VSWR would be sky high here, but actually about 2.0.
Ditto here, 2.0.
And shockingly, 2.0 here as well. I figured it would be the lowest of all, but NOT!
Dual band Ham antenna. VSWR of 1.1 or less on both UHF and VHF bands. See text.
Update: The Ham antenna is noted for not having the greatest bottomside covering. Fixed with 3M "Book Tape".
After dancing around a Ham radio license my entire life, I finally got one! My limited, yet valuable, professional radio experiences helped considerably; of course my electronics background made large parts of the license exam easy. Rules, regs, some procedures, and "Ham culture" took a bit more study! I studied until I knew I'd either ace the test, or miss exactly one question at most.
Both a Ham friend as well as the "VE" (Volunteer Examiner) also suggested that after passing the Technician's test, to try the General test as well - the cost was the same either way. I had taken exactly 4 practice tests for the General (dozens for Technician!), read the explanations for the (many) questions I missed, but that was it. I failed 3 of the 4 practice tests, so I certainly wasn't expecting to pass the real deal, figuring it would do nothing but waste the VE's time. However, much to my amazement - and I think the VE's moderate surprise, I passed the General! I certainly didn't ace it, but I passed it.
I was the first person in the group of 14 prospects who passed the General, several came before me, maybe others passed as well after I left, but now I have to do a bunch more study to be able to use the General ticket correctly. I'm not interested in doing things wrong, I want to be deserving of my exalted status!
So, of course I need a Ham radio in the Jeep - after a bunch of research, and online shopping, I ended up with a Retevis RT-95, a 25 watt dual band (2M and 70cm) Chinese transceiver. I spent quite a bit of time trying to procure an Icom, Kenwood, or similar 50-ish watt dual band radio on the used market, but wasn't successful. I kind of wish it did 1.25m as well - but that's not really necessary for any possible Jeep use.
The Retevis RT-95 is sold under several other names - the best known is the Anytone AT-778UV. Then there is the "CRT Micron", apparently CRT is a French company that sells them mostly in Europe, Midland supposedly sells it as their model DBR2500 - although I wasn't able to locate any for sale. Regardless, they're all the same radio and are pretty well regarded in the Ham community although they're also known to be a bit complicated to operate - lots of features buried in menus! I ended up with the Retevis version as it was the best deal at the time and included the programming cable.
Regardless of all that, I had a problem adding yet another radio (this makes 4) in a tiny Jeep. I already had sandwiched the CB and the broadcast radio/stereo in the dash, and I had mounted the little Midland GMRS MXT-100 on a Hooke Road dash mount bracket. So where to put this one? I ended up with a lesser known product from an outfit called "Arizona Rocky Road". I had originally thought to make something pretty similar from a piece of "Uni-strut", but when I found their "ARR Mount", it was nicer than what I could have made, and wasn't much more money than what I would have spent. I like it and can recommend it!
So while I was at it, since I could probably mount 6 or 8 radios on this mount, I figured I'd relocate the GMRS radio up onto it as well. This enabled me to remove the Hooke Road dash mount, opening up that area for something else (possibly a vacuum gauge). I extended the GMRS antenna and power leads, and installed a Diamond magnet mount dual band antenna for the Retevis. This is where the whole project gets interesting.
Adventures with VSWR
While installing the CB radio, I had had QUITE the adventure with that radio's antenna and a less than optimal SWR meter. I ended up junking the first meter by the simple expedient of putting it under the Jeep and running over it, and replaced it with a much nicer dual needle type. So while I was relocating the GMRS radio, I decided to measure the VSWR of the little antenna that came with it. Much to my dismay, it measured 2.5! To make a long story short, I was able to get it down to 1.5 - not bad - by a simple relocation about six inches from where I had it previously located! I tried several other locations that measured about 2.0, including the middle of the hood which I expected to measure damn close to 1.0, but it didn't. I don't know why - the hood is well grounded to the rest of the Jeep via a ground braid! But whatever, the GMRS could stand a better antenna, but its probably plenty good enough for trail use, and its there!
But wait! There's more! Just for fun, I tried the Ham antenna with the GMRS radio. It is well within the frequency range. Much to my surprise, the VSWR was around 3.0!! Completely unacceptable. I was able to tune it down to about 2.8, but that was it. Even more surprisingly, the Ham radio showed an SWR of 1.1 - or less - with that antenna on both VHF as well as UHF - the same band as the GMRS! I'm damn glad for the 1.1 SWR, but I sure don't understand why I didn't get that with the GMRS radio as well. I can only assume that the Midland's output impedance isn't exactly 50 ohms, and neither is their antenna, but they did a good job matching the two? My Ham friend says SWR is 25% science, and 75% black magic; which has always been my opinion of RF in general. He also says SWR gets even weirder when dealing with capacitive coupled magnet mount antennas - which both of these are!
Retevis mic with hanging loop.
Won't work with traditional mag mount. ⅜" carriage bolt to be converted to mounting stud.
Head ground down enough to fit the mag mount.
Then the threaded portion of the bolt was cut off.
Drilling a mounting hole.
Installed. Crude but effective.
In actuality, the square part of the bolt head could have been ground down more.
Metal strapped to rollbar to accomodate magnetic mic holders.
I used to keep a mic held with a magnetic holder like this in an F-250 - worked great!
Time will tell if this actually works!
If they get bounced off on rough terrain, I'll add conventional mic clips on these flanges for rough driving.
Reprised from previously: Filter for all radios, and power tap for the GMRS.
This was adequate for that transceiver as it only transmits 5 watts of power.
Rebuilt it and beefed up supply wiring for the Retevis tranceiver as it needs 5X the power.
Splicing it in...
UPDATE: A retrofit that plugs into the above harness. Now the radios all shut down when the ignition key is off.
I was able to program my local repeaters into the Retevis using the popular "Chirp" program on a laptop. Incidentally, said laptop has a long dead battery, so it needs to be run off of AC power - the previously installed inverter was perfect for the job!
As seen above, I had to retrofit the mic holder as it didn't have a traditional mounting stud, and the loop style didn't do it for me. So I adapted the ⅜" bolt as shown. I used a carriage bolt as its square shoulder would fit the magnetic mount and would swivel - a regular round bolt would have worked as well, and would probably be better for a standard clip mount where it would be slipped in and out constantly. But this works quite well, although if I had it to do again, I'd probably grind it down a bit more. An M3x20mm bolt was sourced to attach it to the mic, as original but longer.
For $19.99/shipped, who could pass up on this Baofeng UV-5R handheld Ham radio?
Upcoming rear bumper project...
Read on for the next part!