Lscott

That's an interesting point. If I remember right some time ago a guy wanted to setup several GMRS repeaters around his area and CHARGE access fees to use them. Being there are only 8 repeater pair frequencies that consumed a lot of "public resources" for his personnel monetary benefit at every one else's expense.

I have a buddy who picked up one for 800MHz. Cost him $75 at a swap. The use was to monitor the local PD which was on a trunked system. He managed to find the software for it and the one to generate a system key file he said was necessary to get it to monitor a trunked system. The software is out there. Might be sort of hard to find.

They do cause interference. I design high frequency high power switching power supplies for a living. Trying to shield those things is far harder than you think. There are various ways noise can escape from them each requiring their own technique to correct it. That costs money the manufacturer won’t spend on the cheap models, which might be OK for consumer grade use around broadcast radios. However communications grade radios are a lot more sensitive and not all switching power supplies are suitable to use around them. I have a few on the shelf at home I can’t use around my radios for that reason. I don’t care what FCC labels are on them.

Very true. Those USB power adapters likely use some type of switching power supply, which is a huge noise generator, with very little filtering on the output. This is another point too. Most of your 120VAC to 13.8VDC power supplies are also using a switching type design. The ones used for powering mobile radios are specifically designed with more shielding and noise filtering. Some people have purchased cheap ones only to discover later the noise generated wipes out the signals they are trying to receive. There is a reason why the ones designed for two way radios likely cost more so a cheaply priced one may not be the best deal.

As pointed out already USB is only 5 VDC. You can get a DC to DC converter however there is a second problem. Most USB adapters/plugs can only supply 1 amp max. A 5 watt radio will likely draw up to 2 amps at the battery terminals on transmit. The total power drain on the low voltage side of the DC to DC converter will be higher due to the lower input voltage, power in = power out + converter losses, which will exceed the rating for the USB outlet.

Try this forum group. https://groups.io/g/KenwoodRSS/topics You will likely have to register to get access. Once you do then send a message to "Garrett Ramsey". He has been VERY helpful to many people with questions or issues with locked radios. He has helped me a few times. Jan 18 #304

I'm sure a few people here are going to the Hamvention next month. How many are looking at using some kind of digital communications and which specific mode(s)? That would be either using a repeater or just simplex. I have a number of radios that cover the usual ones except for System Fusion so far. I'm assuming the most popular ones are D-Star, System Fusion and DMR. Anyone planing on using P25 or NXDN? I'm thinking about taking several radios but trying to decide which ones.

Makes sense to me. I wonder if a packet network would be allowed? I’m thinking about packet routing if that would be considered a store and forward operation.

Yes, there are some very specific restrictions on data transmissions on GMRS/FRS. I posted about that in another thread about non-removable antennas. However it’s specifically allowed on MURS. Of course the rules also don’t allow repeater operation so that question can’t even come up, and limited to 2 watts. But data transmission is allowed on MURS. Apparently a variety is mentioned in the rules. MURS was created as a Multi Use Radio Service, not primarily, or strictly used, for voice communications. https://www.law.cornell.edu/cfr/text/47/95.2731 While APRS can’t be relayed through a repeater it can still be used on a local basis, like for example search and rescue work, in a limited geographic area using simplex communications. At least that’s how I see it.

I haven’t really used APRS so could you expand on what you see as an issue with using it on MURS, or GMRS/FRS?

http://arrl.net/ ARRL -> Amateur Radio Relay League That's how it was done in the very old days of spark gap transmitters that had very limited range. Messages were relayed from station to station across the country. What is old is now new again. It continues to be done as a message passing protocol. The key is getting a system where the format is consistent and EVERYONE uses the same procedures to pass message traffic. Otherwise it ends up being nothing but a mess.

I looked at the photo of one on the web site. The antennas are obviously molded in with the case. https://www.garmin.com/en-US/p/576031

Humm... There does seem to be an interesting twist to what is allowed for antennas on GMRS radios. It's not specifically related to operation on FRS channels. However it has to do with data transmission which likely most radios don't do. 95.1787(a)4 https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-E/section-95.1787 So if you are looking at a GMRS radio that can send some kind of digital data, lets say GPS location, then you will likely find the antenna is non removable. So yes, my prior comment in general was incorrect, but after looking at the rules a rather narrow exception to allow removable antennas seems to exist. People looking to buy a GMRS radio with built in GPS data transmission for hiking/camping need to watch-out for this for example.

That might be correct. I’ll have to look further in to it.

https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-B/section-95.587

Yes to both questions. Each operator must follow the rules for the class of equipment they are using. So if the radio is certified for GMRS the operator must have his license and ID with it regardless of what channel or power level they are using or which radio service the other station is operating under. A certified GMRS radio will either have a non detachable antenna and reduced power, and narrow band only if it has the ability to operate on channels 8 to 14, or those channels are not included in the radio while the power can be 5 watts on channels 1 to 7 and up to 50 watts on 15 to 22, allow wide band operation and with a detachable antenna. With an FRS only certified radio all of the technical requirements are already built in to the radio and the operator doesn't need to ID, however one might use a type of name, unit number etc for convenience. One thing to keep in mind most GMRS radios use wide band FM, some can select between wide or narrow band, while ALL FRS radios are narrow band only. When using wide band FM to communicate to an FRS radio the audio can be very loud to the point of being distorted. While using narrow band to communicate to a GMRS radio the audio level can be rather low requiring cranking up the volume a lot. When communicating between a group of radios using wide and narrow band FM the large changes in audio level can get very annoying. I use some commercial grade radios for GMRS. Those allow me to program channels in banks, or zones. I have one for wide band FM and another for narrow band FM. So, depending on which class of radio I need to communicate with I select the appropriate zone for the FM band width required.

You do have another option. Yes you can try for your Ham Tech Class license. On the radio side there are some commercial grade radios that are certified for Part 95, GMRS, and also can be programmed for the Ham 70cm band as well. This gives you the option to use either GMRS or Ham using just one radio. Some of the commercial radios are fairly reasonable in price buying used. The other advantage is they tend to perform better that the cheaper Chinese radios. The most important measure is the sensitivity of the receiver and how well it rejects out of band or off frequency signals. Some of ones I own that work well are all Kenwood models. All of the following have Part 95 certifications and will accept out of band frequencies for Ham use. The programming software will show a warning when entering the out of band frequency but will accept it non the less. I've programmed in Ham repeaters down to 440MHz and the radios will operate just fine. TK-370G https://www.manasrekha.com/pdf/TK-270G-370G.pdf TK-3140 https://kenwoodcommunications.co.uk/files/file/comms/uk/brochures/analogue/handhelds/temp/TK2140_3140E_web_V3.pdf TK-3170 http://www.swscomm.com/kenwood/TK-2170_3170.pdf TK-3173 http://www.swscomm.com/kenwood/TK-3173.pdf TK-3180 https://pdfs.kenwoodproducts.com/10/TK-2180&3180Brochure.pdf There are some combination analog/digital radios but they cost significantly more money and more complex to program. Others have some good recommendations for other commercial manufactures, such as Icom and Motorola. So far out of the above my favorite is the TK-3170/3173. They are compact, light, have plenty of channels and not difficult to program. The software is easy to find on-line. The programming cable is the exact same one used by the cheap Baofeng type radios and can use the same accessories like external speaker microphones and antenna adapters. Battery packs and charger base are easy to find. Note the TK-3140 and TK-3180 requires a multi-pin type programming cable and accessories, not compatible with the Baofeng type two-pin plugs.

I don’t know what kind of range you’re expecting out of the radios. The two with antennas close to a full quarter wave, around 6 inches, would have been on my list. The other two with munchkin sized antennas I doubt will perform as well range wise to the other two. That’s assuming they are all equal, in power output, another area where manufacturers don’t generally put that in the specifications.

That looks like the one. The link for the simulated HT case for testing is at this link. https://reflector.sota.org.uk/t/antenna-testing-jig-swr/14791 Looking closer you can see the "long" length of center conductor and shield braid going to each socket. This should have been kept as short as possible. Ideally he could have used one coax cable pigtail for each of the two sockets. There is a comment that the measured SWR's are "High" by 0.7 when verified against a dummy load, likely due to the above issue with the coax cable pigtail wiring. Anyway testing HT antennas isn't going to be so straight forward or easy.

That might be hard to measure, with or without the tigger tail. You would just about need to strip out the guts of the radio and run a pigtail out of it to the SWR meter. I haven’t seen how the manufacturers test their HT antennas but I would guess they do something similar. I ran across a web site where someone built a simulated HT case with antenna connections on the top using a hollow block of aluminum. The test setup wasn’t that good since there was a noticeable length of open wire connecting the sockets together. At UHF that can really screw up the measurements. This topic has come up before on the forum. If you can find some of my old posts some of them have links to web sites where people have attempted to measure HT antennas. If someone wants to give it a try I’m sure others would be interested in the results.

I’ve measured a number of my HT antennas. Originally I thought using a good ground plane would improve the match. Most didn’t, in fact some got worse. Since the human body ends up being part of the antenna system trying to qualify it for measurement purposes is difficult. In one test I did the best match was when the base of the small magnet mounted antenna was resting on the back of my hand held out at arm length. I was using a special small base magnet mount with an SMA connector on it for the tests. For a ground plane I used some sheet metal for heating duct work about 36 inches on a side to simulate a vehicle mount condition. All testing was done using a Rig Expert AA-1000 antenna analyzer. https://rigexpert.net/index.php?route=product/product&product_id=57 Remember for GMRS a quarter wave antenna is about 6 inches long. An efficient antenna to match well is a half wave length long, in the case of GMRS that’s about 12 inches more or less. The metal case of the radio supplies the bulk of the missing half of the antenna, AKA ground plane. Adding a tigger tail likely won’t make much difference unless you have a tiny sized radio. Now if it was VHF there is some benefit seen when used.

You can try removing the antenna from the radio and see if the noise is still present. This will reduce the sensitivity of the radio a lot so the noise source will have to be very close to it. If not then hold the radio up close to the dashboard while moving it around and see if it picks up the noise. You can also try it around the exterior of the truck too. If you pick it up chances are the source is very close to the radio.

By any chance were you using the repeater function? I'm not familiar with the exact radio but I believe you can select between what is call simplex operation and using a repeater. Using the repeater function, which should only work on channels 15 through 22, the radio will try to transmit on the 467.xxx frequencies which is noticeably higher than the frequencies on the channels below that, 1 to 7. That might account for the higher SWR reading on those higher numbered channels. The antenna might be optimized for the simplex only 462.xxxx frequencies. In any case you need to get the antenna up and in the clear to get some decent range out of it. That is critically important at the frequencies used by GMRS.

That should come in handy. Thanks.

Do you have a booth number? There are maps showing the booth layouts and are numbered.