Lscott

I’m just looking for something quick, easy and cheap to experiment with. The power isn’t an issue at VHF/UHF as much as antenna height. People work some of the LEO FM sats with an HT working into a small Yagi for example.

Interesting. I have a KG-UVD1P somebody at a swap gave me for free. I never looked at it. I’ll have to see by any chance it has x-band repeat.

That's what I tried with my FT847. I used it in the satellite mode half duplex. The HT would TX to the base radio which x-banded to the local repeater. The HT would then RX the repeater's output directly. No issue with worrying about the ID requirement since I always went from the HT to the base so when I ID'd the base would of course be ID'd as well. The part with the HT which has to operate split band, TX on one band then RX on the other. My big disappointment was the Kenwood TH-D74A. You can't program any of the memory channels that way. The TX and RX frequencies have to be on the same band. Since it does have two VFOs, RX sections, it can still be setup to sort of work that way but it's a lot more of a hassle. It's one of the reasons I still keep my ancient TH-G71A around and several CCR's. That radio is very easy to program for split band operation.

This one claims it has the function if it really works. https://www.retevis.com/RT23-Cross-band-Repeater-HAM-Radio

That's the other issue with cross band repeat operation, the ID problem. I don't know of any radios that have the ability to TX the call sign as required when TX'ing from the repeater to the user's radio. The repeater's TX has to self ID on the Ham bands. My interest is something I can slap together quick. For example using a x-band radio on a balloon or kite for field day.

I just picked up an old Kenwood TH-79A really cheap at a local swap the other weekend. After getting the documentation in pdf format off the Internet I saw it has a cross band repeater function built in. This is NOT the same as cross band operation, but a true repeater operating V/U or U/V. I've experimented a bit using a cheap controller, 2 HT's and a diplexer but was looking for maybe something a bit more simplistic. What current production hand held, not mobile, radios have this feature? I found the Retevis RT23 claims to have it and is fairly cheap as CCR's go. I'm not interested in issues concerning duty cycle. Just whether the radio has the basic functionality and how well it works.

So if there are experimental GMRS repeaters running digital modes under a special FCC license authorization there must be users too. While not currently authorized by the FCC for general use some of us have multimode radios that can receive one or more of these digital modes. If we knew where these repeaters were located it would be fun just to monitor the testing.

One of the first FCC Part 95 certified radios I got was a used Kenwood TK-370G-1. https://mra-raycom.com/wp-content/uploads/simple-file-list/Specifications/portables/TK-270G-370G-Product-Brochure.pdf

I was talking to some buddies at a weekly coffee break I go to which are all Hams. Some think the Monroe Michigan swap in June is going to be really popular. I tend to agree. It normally is but this year I think it’s going to get mobbed.

Right now only in Oregon State, otherwise you have to keep it in the original shipping plastic bag it came in when using it. 8-)

Glad you had success getting the out of band frequencies to work on your Motorola radios. The Kenwood software works about the same. If you enter a frequency outside the of the official range you get a warning message that pops up. If you click to dismiss it the software will accept the entry. It gets tedious when you have a lot of them to enter, but at least it works. I suggested to a fellow Ham to build a test code plug for a radio he wanted to push petty far out of the official range. Put in frequencies, starting at the boundary of the official range edge, about every 1 MHz apart in successive memories. Then try each one out to see where the radio’s PLL fails to lock, you get a warning tone out of the radio in that case. No guarantee the same range works on another radio of the same model due to component tolerances. Once you know the limits the next question is power output and sensitivity as you mentioned. That depends on the power amplifier’s output filter band pass characteristics, and the RX section’s filter. On some radios the power amp filters can be “tweaked” a bit provided the components used have adjustments. The RX section maybe. Many of the Kenwood radios I’ve looked at use some type of electronically tuned band pass filters. Those I doubt are easy, if at all, possible to tweak. The tuning voltage is likely non linear with the precise value generated by the radio’s micro using an internal formula or look up table.

The important point is paying attention to the amp rating of the fuse. Too low and the fuse will fail. If the fuse is rated close to the max current the radio will draw the heat buildup will eventually fail the fuse. Remember that a fuse is a thermal device, an element has to melt to open the circuit. Fuses operating at elevated temperatures may also fail at current levels below their rating. The voltage rating on the fuse is the max system voltage where the fuse is guaranteed to clear the fault without excessive arcing. Using a higher voltage rated fuse should not be an issue.

Did anybody consider trying the Kenwood TK-3360, or the older model TK-3160 radios? They have about the same feature set as the basic VX-261 units. https://www.motorolasolutions.com/content/dam/msi/docs/EA_Collaterals/ENGLISH/commercial/portables/vx260_series_spec_sheet_ea.pdf The Kenwood radios will do wide and narrow band FM, use various battery pack types including Lithium Ion, plus all you need is a cheap Baofeng type cable to program them. In fact many of the cheap Chinese radio accessories, like speaker mics, work on the Kenwood radios. The software I found on line to down load fairly easy. The VHF models work nice as MURS radios, make sure the power is set to low, with enough channels left over for NOAA weather monitoring. https://www.kenwood.com/usa/Support/pdf/TK-2360_3360.pdf http://astralcommunications.com/site/wp-content/uploads/2013/01/TK-2160_3160.pdf I see the UHF version radios selling on eBay frequently in various states of condition, some are the full package, radio charger, battery pack and antenna. As I've mention before Kenwood radios will program outside of the stated band split. So if necessary even a few Ham 70cm frequencies can be used.

I don't know about Vertex or Motorola radios how the frequency range is verified, but with Kenwood I do. Maybe Vertex or Motorola radios are similar. The radio programming software reads the code plug which has the radio's model number and sub type embedded in it. When the software tries to write the code plug to the radio it first queries the radio for model and sub-type. If the two don't match the software generates an error message. One version of the software with the license key I used for installation even offered to let me change the "market code" changing a radio from a European or Asian model to a US type! The service manual claimed if you used the wrong model type, and the associated market code, to program the radio "the first time" it can't be changed later. Apparently that's not true if you have the right software. Some of the Kenwood radios use "XOR" encryption on the code plug contents I discovered, for example the popular TK-3170 and TK-3173 radios. After some lucky guesses and looking I found where in the code plug the encryption key is stored. It seems to be located in the same place even between totally different radio models. I suspect the software programmers used the same code plug file structure for the beginning section across model types. The key however can vary from code plug to code plug even for the same model type. After decrypting the code plug the version of the radio software, radio model type and the installation license key, used to install the software which created the code plug, was found. The frequency was stored in little Endian integer BCD format. For example 462.67500 MHz was stored as 00 75 26 46, two BCD digits packed into each byte. Any passwords set in the radio, such as power up enable, radio read or radio over write are also stored in the code plug. Without the engineer's license key for example even if you loaded the code plug in to the programming software the radio over write password is blanked out with asterisks. If you know where to look in the decrypted code plug even that password is in the clear and can be recovered allowing a radio to be reprogrammed. The software will prompt the user for the password if one is used and will refuse to either read the radio or over write the current code plug depending on which passwords are set. The channel names, group names, strings in general, are stored in normal ASCII format. Other options and features are likely stored as bit fields or some other type packed data structure. Since none of this will ever be documented by the manufacture so a good deal of experimenting has to be done to reverse engineer the code plug further.

I would like to see the results just to satisfy my curiosity.

Yup, that's the deal. It's really your choice. Most likely the radio's you'll find being sold are the -K type, Part 95 certified, anyway.

That's true. If you don't mind forgoing the Part 95 certification the other band split will work just fine plus gives you full access to the complete Ham 70cm band. I found the other band split I can program my radios down to around 440MHz which covers a lot of the simplex frequencies and the repeater section of the band just fine. Most of the radios you find are the -K type. The programming software you need is the KPG-89D, which I have since it's the same software used on the TK-3180 hand held radio I have. The version I found, V1.61, has the so-called "engineer's" key allowing the bypass of any passwords set in the radio and access to a few more features the usual dealer or end user version doesn't allow. The software installs and works fine on Windows 10 as well. You just need to find a programming cable. Some people here have a good recommendation on where to find one.

One of the first things I do when thinking about buying a radio I'm not familuar with is go look for any manufacture's brochures. They are a good source listing the radio's main features. For the TK-8180 look here. http://www.swscomm.com/kenwood/TK-7180_8180.pdf This seems like a very nice radio.

It would be of interest to see just how much attenuation you actually get. Normally the filter is tuned to get as deep a notch as possible. These cheap Chinese notch duplexers are only spec'ed for 70db or a bit more. The wider the bandwidth the less notch depth you get. Some of the more expensive band-pass band-reject filters have attenuation levels of 90db or more at 50 watts for example. At 5 watts you "might" get away with it in a quite RF area whereas using the same filter with a higher power transmitter may not work. Remember one of the notch filters is used to keep any side bands, phase noise, generated by the transmitter from getting in to the receiver section. In fact knowledgeable people building repeaters stay away from particular models of radios because the transmitter section generates too much crap the filters can't eliminate.

I have a number of commercial Kenwood hand held radios and one mobile. While it did take a bit of searching on the Internet I have managed to find the programming software on line to download. So far I have the OEM software to program the following UHF Kenwood radios. TK-370G TK-3160 TK-3360 TK-3140 TK-3170 TK-3173 TK-3180 TK-D340U NX-340U NX-820HG (mobile) One of the nice things about the commercial radios, at least Kenwood with Motorola not so much, is the ability to program in frequencies outside of the official band split specifications. That allows using the radio for both GMRS and Ham Radio's 70cm band, both TX and RX operation, for those that are dual licensed. The purposed built GMRS specific radios typically don't allow this and could be a factor is which radio you select. Many of my radios have GMRS simplex and repeaters programed along with a bunch of Ham 70cm simplex and repeaters too. Just have to remember which call-sign to use depending on the memory channel in use. 8-) The main problem with using free software like Chirp are some of the radio's features are not supported, or what support there is happens to be buggy. Waiting for Chirp bugs to get fixed, well some never do seem to get fixed. The developer for the module for that particular radio lost interest, doesn't have the time or doesn't have access to a radio to reverse engineer the communications protocol and code plug. Some of the developers are "loaned" radios to use for a period of time then have to return them to the owner(s). If you want to make sure you have full access to a radio's operational features there is no substitute for the manufacture's software, and this is VERY particularly true for commercial radios.

These radios don't seem to offer anything much different that some of the Kenwood commercial radios. You can look for the TK-3360's analog only or the TK-D340U analog/DMR. https://www.kenwood.com/usa/Support/pdf/TK-2360_3360.pdf https://comms.kenwood.com/common/pdf/download/DMR_TK-D240V_D340U_K_letter_1124.pdf You can find the TK-3360's, and the slightly older TK-3160's, on ebay for decent prices. https://www.urci.com/downloads/kenwood/kenwood_tk_2160_3160_brochure.pdf I just recently picked up a used TK-3360 for $30 including shipping, used battery pack and no antenna. There are good deals out there, just have to be patient and look for them.

I would be interested in knowing how deep the notches are for the duplexer. The typical cheap Chinese ones they use are spec'd for around 70db and that's at a very narrow bandwidth. To get a 500KHz bandwidth I suspect the notch depth is rather poor, traded off notch depth for bandwidth, leading to poor performance, i.e poor off frequency rejection and RX desense from the TX side. My understanding is the TX side of the notch filter should be tuned for the exact RX frequency for maximum notch depth while the RX side of the filter should be tuned for maximum notch depth at the TX frequency.

I admit I have one of those. The radio hardware is ok. The programming software sucks. I’m tired of the bugs. They fix something then the next version it’s buggered up again, or something else is now broke. I haven’t touched mine in over 6 months.

I don't know about Motorola but some of the Kenwood radios the code plug is encrypted too. I found out it's a simple XOR type encryption using a key byte stored in the code plug. For the several radio models where the code plugs are encrypted that key was always stored in the same place. Using a hex editor to load the code plugs and the data manipulation tools I was able to decrypt the code plugs easily. Maybe Motorola does some similar.

You have any links to information on this? I find it hard to believe this can happen unless who ever tweaked the radio down some how botched the internal settings. The power brick spec sheets I've looked at show a bias pin that controls the power output. I a few of the Kenwood HT designs there is a feedback loop that measures the current through a set of low resistance resistors. The voltage developed goes into the feedback loop to adjust the bias pin voltage to keep the power output on the module constant. At least that's how it looks to me in the service manuals. Some of the power modules are static sensitive and you can blow them if you're not careful. There is also a warning about getting the pins too hot while soldering which can also bugger up the module.