Lscott

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

What you really want to know is which type is it. TK-8180-K1 (FCC ID's K4437313210 and K4437313110) TK-8180-K2 (FCC ID's K4437313220 and K4437313120) You can check the detailed FCC certifications by typing in the above FCC ID's into the following website, then click on search. https://fccid.io/ The difference is the "band split", the frequency range over which the radio is specified to work. The -K1 type is either a 450 MHz to 512 MHz or a 450 MHz to 520 MHz model depending on if its the lower or higher power model. Both are FCC Part 95 certified, legal to use for GMRS. The -K2 types are only certified as Part 90 radios. Both types will do wide or narrow band FM. Before buying a radio I normally do a search for the manufacture's sales brochure. They are a good source to see what the general features and the technical specifications are for the radio in question. In your case look here. This saves a lot of time asking for info. http://www.swscomm.com/kenwood/TK-7180_8180.pdf When buying a used radio make absolutely sure you look at a photo of the radio's name plate, which shows the exact model type, FCC ID and serial number. It's not uncommon for sellers to screw up the description, in at least one case for me a deliberate case of misrepresentation, the seller shipped a radio that did not match the name plate on the one in the ad photos, different band split which was totally useless for my needs, I did get a full refund through eBay. In another case the radio was not FCC certified, no FCC ID, it was an European type that required a different version of the software to program it, which was hard to find. That radio works fine but is an odd ball in my collection. The code plugs from the US and European types of the same base model are not interchangeable so I have to maintain two versions for this one. One more thing about buying used radios, passwords. Almost, if not all, commercial radios can be password lock preventing the radio contents from being read out, which almost nobody really cares about, and the second prevent the radio from being reprogrammed with a new code plug. If you get a radio with a write password, and you don't have a version of the programming software with an "Engineer's" level install key, you can't load a new code plug in the radio. Your only options is find somebody who has the software to bypass the password or take it to a radio shop, or Kenwood service, pay a ridiculously high bench fee for the tech to do 5 minutes of work clearing out the old passwords. I've had a few radios like this that where I have the software to bypass the passwords for those models. The seller may not even know if the radio is password locked or not. You can ask before purchasing and see if they know for sure or not.

These are the brochures for the TK-2160/3160 and the TK-2360/3360 radios. http://astralcommunications.com/site/wp-content/uploads/2013/01/TK-2160_3160.pdf https://www.kenwood.com/usa/Support/pdf/TK-2360_3360.pdf

My favorite Kenwood models, for VHF use, are the TK-2170's followed by the TK-2140's. The UHF versions work fine on the Ham 70cm band and should work down to about 440 MHz which covers most of the simplex section and the repeater section of the band. The radios may function lower. You'll need to test your radio and see what it will function down too. https://www.icomamerica.com/en/amateur/amateurtools/US-BandPlan-Update-1-2020.pdf The UHF models come in several band splits, most common is the 450 to 490 MHz or so ones. There are some other radio models that work from 400 to 470 MHz, but seem to be really rare to find. The 16 channel radios are OK if you want something simple to use. They're good for programming in your local repeaters, keeping in a glove box or handing out to family members. There are 2, 4 and 8 channel radios out there but personally I'm not interested in those due to limited channel capacity. The 16 channel models I would consider as the minimum usable. The issue with any of the commercial radios is they DO NOT have a VFO like a Ham specific HT would. Some of the radios can be modified for "front panel programming", which requires removing a diode or resistor from a circuit board plus enabling it in the software, but the actual programming must be done to an empty memory channel. The procedure is rather cumbersome and covered in detail in the radio's service manuals. I've never modified any of my radios, easier to use the software. One work around however is to program a sequence of memory channels using the channel spacing for the band used. On UHF it's typically 25 KHz. So I would start at lets say 440.000 then the next memory channel is 440.025 etc. The channel name would be the frequency like 440-000, 440-025 etc. That gives a decent simulation of a VFO using a fixed step size. The radios have "zones" where you can group channel memories together. For the simulated VFO I stick them all in their own zone labeled "SIMPLEX" for example. The better radio for this is the TK-2140/TK-3140 series since they have a total of 250 memories. The 128 channel radios it gets a little cramped. https://pdfs.kenwoodproducts.com/9/TK-2170&3170Brochure.pdf The below is the same as the TK-3170 but has trunking, which you'll never use, and uses the same software. Works very well for GMRS too. https://pdfs.kenwoodproducts.com/12/TK-3173BrochureRev.pdf The below radios use the multi pin connector, like some Motorola radios, for the speaker mic's and programming. http://www.swscomm.com/kenwood/TK-2140_3140.pdf There are some higher end Kenwood radios that you'll end up paying more for used with extra features you'll likely won't use except for the higher channel capacity. https://pdfs.kenwoodproducts.com/10/TK-2180&3180Brochure.pdf The below radio is like the TK-3170 but has a more basic feature set. https://sieuthimasomavach.vn/upload/tk22123212-brochure.pdf Whatever you buy DO NOT purchase any Kenwood "Protalk" radios. They are normally only 2 watts and come setup with a list of programmed frequencies to select from, which you can't change. The frequencies are all from the business pool, none are useful for Ham or GMRS use. You'll see these being sold at times with what looks like a good deal, until you discover the limitations, then they end up in the junk draw. Fortunately I did my research before purchasing when looking at an unfamiliar radio model to add to my collection and avoided the mistake. If you're interested in Motorola, Icom or Vertex commercial radios there are some experts here on the forum, I'm not one of them.

If you're interested in the Kenwood VHF models many will cover 136 to 174 MHz natively, no out of range warnings from the software. These are great for Ham 2M band, MURS, NOAA weather and the VHF marine channels. Of course the radios only have Part 90 certifications so user beware. They are also somewhat harder to find and seem to command a higher price used. The newer replacement for the TK-3160 is the TK-3360. It has a few extra features plus 5 watts output on UHF compared to the TK-3160's 4 watts. Both are 16 channel radios, but neither are Part 95 certified, just Part 90, however. If that doesn't matter they make great basic GMRS radios that a kid can use without screwing up the settings when programmed right.

I've experimented with a thin walled fiberglass mast in a heavy duty speaker tripod mount for a temporary setup. There is an AL-800 dual band telescoping antenna on the top. The top tubing section was a bit thin so I removed. As it is now I get the antenna up about 20 feet when mounted on the tripod. If its a bit windy a few 6 inch tent stake spikes with some nylon cord works to guy the mast so it doesn't blow over. https://www.dxengineering.com/parts/mfj-1911 The antenna seems to match up OK on the GMRS channels when the coax is attached. No ground plane is needed thus reducing the wind load. https://www.dxengineering.com/parts/pry-al-800 The mast pops out of the tripod and will collapse to about 4 feet. The tripod folds up to about the same dimension. Without any guy wires I can setup the whole thing in about 10 minutes. I ran RG-58 cable up to the antenna. While a bit high on losses it is light weight and I'm not running the cable far anyway. I made the trade off with higher losses to get a light weight easy to setup and transport portable antenna system. If I have to I can use a 30 to 40 watt FM only amp that needs 4 to 5 watts drive power from an HT while drawing maybe at most 6 to 7 amps DC current, low enough to supply from a modest sized 12 volt battery. For Ham use a Mirage dual band BD-35 amps works. For GMRS a wide band amp is necessary. One from BTECH will work, however it is not Part 95 certified. https://www.dxengineering.com/parts/mir-bd-35 https://www.miklor.com/COM/Review_DMR-Amps.php https://baofengtech.com/product/amp-u25d/ If you look around you can find good deals on the above used. I picked up a BD-35 and a U25D for $100 total at a recent Ham Radio flea Market.

I have a Ham Radio buddy that is interested in a cheap P25 radio mainly for monitoring public safety frequencies. The downside in many public safety departments run encrypted so you won't hear anything without the keys. I stumbled on a series of posts concerning NXDN. Apparently each radio has a unique ESN, electronic serial number, that a trunked radio system can verify. If I remember right a radio that is not authorized on the system will hear NOTHING. The software for setting up the system requires getting a key file for the radio and a license key from Kenwood to enable a radio on a trunking system. Sort of takes the fun out of using a radio just to monitor a system. I guess that was the goal to maintain security.

I haven't made any of my own screen protectors. I do look for radio cases that have a screen cover. A number of my used radios obtained had noticeable scratches on the plastic screen. I found out that using tooth paste as a rubbing compound will take out the scratches if done right. It does take a lot of rubbing and the right technique to get good results but it does work.