General antenna Mods

I’m having a hard time finding any reviews regarding modding Frs/Gmrs radio antennas. I know that the FCC does not allow Frs radios to have matched antennas, but Gmrs can have matched antennas. When they combine Frs and Gmrs into one radio having a matched antenna is negated. I have specifically been looking at the Midland gxt900vp4, and it doesn’t seem to have a removable antenna. Maybe this type of modding is easy and needs not any real guides dedicated to it, or I’m not looking hard enough. If anybody has any advice please reply.

The GXT900vp4 does not have a removable antenna as you already guessed. Modifying the antenna is against FCC rules if the modification extends the power beyond the 5370.2 mW it currently outputs, listed on page 43 of the SAR report. It also states that “The measured peak output power should be greater and within 5% than EMI measurement.”.

I bought a pair of MURS (free license) two-way radios (Dakota Alert) that do have detachable antennas, allowing a greater then 2 W output that it currently has. I will purchase a base station that I can really get aggressive in antenna purchases if I choose.


I already knew that it was illegal as previously stated in my original post, but that won’t stop some. The reason why I want to modify my antenna is because of a recent biking accident. The group of friends that I was riding with all had some sort of old motorola frs radio. We all were going at our own pace, so most of the time we were alone, and I ate it pretty hard on switch backs consisting of rock and larger rocks on a trail 13,000 ft up between Angelfire and Taos New Mexico. After I had fallen I went to radio anybody in my group for some first aid equipment and the only person that could hear me on the radio was my buddy who was already at the bottom of the switchbacks. In the end I was fine, just a real nasty charlie horse on my butt and my big toe on my left foot has been numb for the past 2 weeks and is slowly getting the feeling back. I just want to make sure that we can radio each other better than before.

Again… ANY modifications to said radios are illegal. While GMRS rule allow for external antennas, any FRS/GMRS radio cannot be modified, as it will void all type-acceptance. FRS allows NO external antennas at all.

Your best bet is to get a commercial grade radio with a removeable antenna.

You do have a GMRS license…,. right?

FYI: The MURS radios will not talk to FRS/GMRS radios. Different frequency band. The FRS/GMRS radios are preprogrammed, and the frequencies (channels ) cannot be changed. You can purchase lots of radios that can accept the MURS frequencies, and they can be programmed for your specific needs.

The overall problem I see on this post is most everyone wants the FRS radios to much more than they were designed to do. They are low powered, low quality radios and were really designed as “family” radios. You know, keeping up with each other in the mall, Wal-Mart, etc. They were not designed to talk several miles down the highway (even though they greatly exaggerate the range). If communications is important to you, step up and buy commercial grade radios. They cost more, but the quality and durability are worth the extra money, plus they will last for many years. Buy a 4 or 5 watt unit, file for the FCC license (good for 10 years) and have many years of happy communicating.

I have a bunch of Midland G-11 and Cobra PR2000WX GMRS radios that have removable antennas :wink:

Hey jgg204, do you still have the cobra PR2000WX radios?

i thought the fcc gmrs license is for 5 years… i am a noobie is a commercial license different?

It is 5 years, and there is talk of removing part of the fee.

The overall problem I see on this post, or for any radio / transceiver is most everyone wants to be able to utilize them to their fullest potential.

In theory, if one may augment a radios antenna. With a standardized bnc, sma or other connector one would might possibly unsolder the existing curly antenna, and solder the connector ground to a grounding pad on the radio, and the pin/tip/center to the pad on witch the curly antenna may have been removed to the center of the connector.

On the connector side of the proposed antenna, one would most likely use the size of stiff wire that just fits in the center for soldering. One may then measure the wire exposed from the connectors shield to the following theoretical sizes.

For ¼ wavelength 6-1/32 inch
For ½ wavelength 12 –1/8 inch
For 5/8ths wavelength 15-3/16 inch

One could possibly tune the antenna to give you the best performance it can.
With radio shack swr meter #: 21-534 or similar and possibly bnc adapter 278-120.

Channel 15 is the lowest frequency,
channel 22 is the closest center frequency, and
channel 14 is the highest frequency. One would tune the antenna just like for cb’s

One may possibly mount the external antenna on a stick 10 to 15ft, the higher it is, the more direct line of site you will receive, one could possably use this for camping utilizing a radio as a base station, but also have more possibility for signal loss due to cable loss. one could use the measurements above in a collinear antenna with similar to website . One may also try radial grounds similar to website

I have not tried this, but just used a calculator and standard equations for this theoretical construction, this may not be any better than the curly antenna supplied, as it itself was maximized for its size.

Ok, we are getting into an area here that is a bit touchy. We appreciate the interest and the technical aspects of this… however:

"Modifying certain types of radios, including equipment approved for GMRS use, is illegal. That is a fact. How you feel about this law as well as whether or not it is actually enforced is irrelevant. Having these topics discussed here could potentially cause problems for us, so we’re going to have to set and enforce some specific rules on what will and will not be allowed on this topic:

Discussion concerning the law itself, for example why you feel that it is good or bad or enforced or not enforced, is permissible.

Discussion, without specifics, of the performance (or lack thereof) of components of certain radio models and how performance could potentially be impacted with a different/better component is permissible. For example: "The antenna on radio X is terrible. With a better antenna, I expect the range would improve 200%!"

Discussion of tweaks or modifications with specifics that could be replicated or used by others to modify radios is NOT permissible. On the first offense, users violating this rule will be warned and their post will be removed. A second offense will result in a ban."

Sorry to have to come crashing in on this.

That is okay… as a matter of fact, the moderator has expressly forbidden any discussion on modifications, as they are illegal.