Lscott

One can also try a corner reflector type gain antenna. Look for “Corner Reflector” in the menus and click on it. They’re not very big for the gain. http://arrowantenna.org

If you like to experiment and design antennas some good simulation software helps. I’ve used various versions of EZNEC+ up to V6 for a number of years. The software will be free starting in 2022. The guy who wrote it explains why, he’s turning 76 and wants to retire and doesn’t want to deal with it anymore. https://www.eznec.com/

I found using tooth paste as a VERY mild polishing compound works to get scratches out of plastic screen covers. Got out some mild ones on several of my used radios I thought would never come out. You should practice on a junk one to get the technique right otherwise you just end up with a lot of fine “stroke” marks on the screen.

So it's a one time deal? Listening all you want, then TX for 20 seconds and it dies never to work again?

Looking at the photo the plug is like several I have. The knurled nut on the end around the center pin likely unscrews. Typically there is a fuse in there. It might be the fuse is toast.

I thought of that too. There are plenty of radio shops that do just that. Some run a trunked repeater system as an extra cost option for their fleet radios. The appeal to the user is they don’t have the cost to install one or have to administer the system. With 5 or more repeaters in a trunked system on a tall tower you can handle a lot of users. The radio shop just assigns different customers to different groups. If I was renting radios I would make sure there was a requirement in the contract the radios must be wiped before being disposed of or rented to another customer.

What you said is true but that wasn’t my point. When the license expires that’s it, done. Now get a business only frequency. There should be no renewals. As it is most of the traffic I hear on FRS, family radio service, are business and rarely family or personal use.

That's what I suspect with a lot of the used HT's you see for sale. Companies upgrading their system, in the case of NMP you pointed out, to a digital system. They dump their old analog radios on the surplus equipment buyers market, who then turnaround and try to flip the radios for a quick buck.

Part of the fun collecting used HT's is trying to figure out who the previous owner/user was of the radio. Most of the time all you get is some frequencies listed, maybe the radio has provisions for a display so that might help. The Kenwoods I collect typically have an entry for 2 lines of 32 character data each that you can only see when reading the radio. Those are normally blank, but a few had something entered. A TK-3212 I acquired only had 14 frequencies in it along with the display names for each channel, nothing else was found in the code plug when the radio was read. After doing some detective work, a lot of searching through the FCC's database, I found an entry where "NMP" corresponded to the first 3 words in the company name, one letter each. The license it fell under was WPTP616. https://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=2363642 https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseLocSum.jsp?licKey=2363642 The frequencies also seem to match up. As you can see there is a unit 1 and a unit 2 in the FCC database, and in the code plug you see "U1 OPS", "U12 OPS", "NMP RAD", "NMP ADM" etc. Things looked like they all sort of made sense. NMP -> 9 Mile Point (Nine Mile Point) RAD -> Research and Development (For a nuke station you would figure something this would be going on) ADM -> Administration T/A A -> Talk Around Channel "A" The radio I got used off of eBay apparently was previously used at a nuclear power station. I joked with a few fellow radio buddies that I should check it with a Geiger Counter to see if anything happens. When companies dump used radios I'm surprised they don't get the code plug wiped clean. At lest in the above case it likely would have been advisable. Just enough info was there, some lucky guesses and detective work, and I'm fairly sure about where the radio came from.

The main issue with testing HT antennas is duplicating the coupling between the radio and the users body. Yes, the users body is part of the antenna's ground plane, and it makes a huge difference. I've done the experiments myself. Some of the antennas were screwed into a "SMA" magnet mount, yes they are around, then placed on a 30 to 40 inch square metal sheet for a ground plane. On a few of the antennas tested the SWR was over 3 or 4 to 1. Removing the magnet mount from the metal sheet and placing it on the back of my hand reduced the SWR to under 2:1 in some cases. The below links are what others have tried. https://www.hamradio.me/antennas/ht-antenna-comparisons.html https://reflector.sota.org.uk/t/antenna-testing-jig-swr/14791 https://www.ko4aje.com/ht_antenna_tests.html https://kd9nrt.com/2020/07/09/antenna-comparison-test/ http://www.km4fmk.com/NewAntTesting.html

That's my thoughts as well.

I have a Kenwood TH-D74A I got because it was tri-band with D-Start being a bonus. I haven't really used D-Star. I picked up a used Kenwood NX-340U, a type 2, at a bargain price on eBay a while back. It does analog and NXDN. https://comms.kenwood.com/common/pdf/download/05_nx240v_340u_K_1117_typeD added.pdf I also had a buddy that gifted me with a surplus mobile NX-820HG, a type 2 model that covers 400 MHz to 470 MHz, good for covering the whole Ham 70cm band. I haven't even turned it on or tried to program that one yet, but I did do a preliminary code plug for it. The spec's claim that the wide band analog mode in not available in the US. The hacked radio programming software I found allows it making the radio more attractive. https://www.ameradio.com/doc/Kenwood_NX-720HG_NX-820HG_brochure.pdf I'm leaning more towards DMR myself since more radios seem available for it at reasonable cost. Yeah most are Chinese, which I think sooner or later will just improve with time. Some of my buddies have DMR radios, one has a Motorola XPR-6550 he got used for around $350. https://www.aircomm.com/downloads/motorola/motorola_xpr6500_specsheet.pdf In that area I have a D878UV dual band from Anytone. I also picked up, again real cheap, a Kenwood TH-D340U which does analog and DMR. https://www.bridgecomsystems.com/pages/anytone-at-d878uvii-plus https://www.space-comm.net/img/pdf/TK-D240_D340.pdf The D878UV radio hardware doesn't seem too bad, the firmware and in particular the radio programming software is buggy. If you look at the firmware releases they seem to come out with a new revision about every 3 months. http://www.wouxun.us/category.php?category_id=93

The reason I mentioned this example is to show not every business using GMRS frequencies are licensed to do so. Sort of hard to believe that since 10/2015 nobody complained to the FCC. You don’t hear them except occasionally. Unfortunately that frequency is the same one as a local GMRS repeater, which I use, but has a different PL tone. That repeater has around 80 registered users to date and about 8 miles or so from the one at the mall.

And there are some still active using the band with an expired license. The mall close by me is still operating. I monitor them all the time at home and when I'm walking around the mall. The frequency is used by the mall's house keeping staff. They use it to communicate between house keeping staff and the mall's security office. https://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=3354643 (Security) And yes I've heard the mall's security dispatch office on it a few times. The mall's security does have a current license for their own frequency so either they have two radios or their dispatch radio has both sets of frequencies in it. https://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=194751 (House Keeping) Click on the "Admin" tab then scroll down to the section labeled "Special Conditions". There you'll clearly see they were originally licensed for GMRS but never renewed. Note the frequencies are for a repeater, and yes they are using it too. Their license, KAB1523, expired on 10/12/2015. I guess the FCC doesn't give a crap.

If you can provide more details of how they are connected and maybe some photos it would help.

Some of the Kenwood radios I have with LTR are: TK-3140 TK-3173 (Same radio as TK-3170 but with trunking.) TK-3180 All have Part 95 certification.

I have several different model HT’s with working code plugs I can contribute.

If there was a file section reserved for sample code plugs that would likely be of help. The code plugs aren’t big. Wouldn’t take much to setup a folder with sub folders broken down by manufacture and model type. I’ve PM a few people on the form doing just the above, sent them a code plug I’ve used on the same model radio they can use as a starting point. A new, or old user, could download a working sample code plug to read into their radio’s programming software. Once that’s done the user could just modify it for their specific case. Since the frequencies are all known copying an existing memory slot to an empty one with most likely changing the tone is all that’s required.

The legal basis I’m not so sure if it would pass under the FCC rules. This is my reason for asking if anybody knows of such a system in operation with the FCC’s blessing. The radios are transmitting digital data using sub audible signals to the trunking system’s repeater. Also what I read the repeaters are sending digital data out every 10 seconds on an open channel. See the links in my opening post. The FCC has some requirements, limits, on the duration, frequency and type of digital data that can be transmitted. Somehow a burp of digital data every 10 seconds will effectively preclude having another conventional repeater on the same channel. I don’t think this would be compliant with the rules.

Never though about using LTR as a means for repeater access control while ignoring the multi-repeater bit. That would seriously screw with repeater jammers and unauthorized users.

I don’t recall seeing this topic covered. Has anybody seen a “trunked” GMRS repeater system? https://en.wikipedia.org/wiki/Trunked_radio_system Several of my radios have “LTR”, logical trunked radio functionality builtin. There is also such a thing as LTR-Net which networks several trunked repeater systems together. https://www.twowayradiodirectory.com/ltr.html I know this requires several repeaters and there are only 8 channels reserved for repeater use so it is resource intensive. People are networking GMRS repeaters together so a trunked system isn’t that much more of a stretch.

I suspect this the case. I’ve looked at the FCC grants for several of my Kenwood HT’s. They come in several different band splits. The models where the lower “official” frequency limit is 450MHz had Part 90 and 95 certification while the 400MHz-470MHz models did not, typically just Part 90.

Does anybody own one of the 900MHz Retevis radios yet to give a first hand opinion on them?

It looks like a type 1 radio. I verified that by looking up the FCC ID to be sure. The certification shows what power levels, bandwidth and frequencies the radio got the certification for and the relevant FCC Part code section. https://fccid.io/K4437313110 I think this radio would be just fine, this is the 30 watt model and FCC certified for Part 95. Now all you need is the software, programming cable and hopefully the radio comes with a usable microphone.

If anybody wants to experiment with the radio's firmware just look here: https://github.com/open-ham/OpenGD77