Lscott

At UHF, that's where GMRS operates, antenna height is the BIG issue. While more power may help if there are obstructions between the two stations using a better antenna and high enough to clear local roof tops will pay off. To give you an idea of how far you may expect to communicate the site below will give you some idea. As you can see from the examples holding two radios by hand, 5 feet, you're lucky to get 6 miles. And that's with no obstructions! I have talked mobile to mobile and got reasonably clear communications using an external magnet mount antenna of around 5 miles at 5 watts on VHF while driving on an open highway. Past that the other station began dropping out. The other station was using a similar setup. I would expect on GMRS, UHF, about the same performance. http://www.hamuniverse.com/lineofsightcalculator.html I would also recommend you look into getting a better radio. You will find lots of suggestions here where most people recommend a good quality used commercial grade, Part 90, radio. Some are even FCC certified for Part 95 so there is no question about their legal use on GMRS. While many people buy the inexpensive Baofeng radios they don't have the best performance. I have several Chinese radios I play around with. For not a whole lot more money you can get a much better quality radio. I have several Kenwood TK-370G-1 radios that are FCC part 95 certified, 128 channels, narrow and wide band per memory channel, and 4 watts. I have near me a DMR station that routinely breaks through on multiple frequencies on the cheap Chinese radios, but doesn't do it on my Kenwoods. That's the difference a good receiver makes.

How about some how to, or tutorials, on basic topics. GMRS is mainly aimed at non technical people who simply want a good means of communications and don't have much interest in the theory or radio as a hobby. For that there is Ham Radio. For example one wants a mobile installation. Basic info on how a mobile radio should be wired up for electrical safety, battery connections, fuses etc. What type of coax cable to use, cable connectors, antenna location and antenna mounts. Recommended mobile radios, antenna manufactures and models. Some sample photos of other people's installations for ideas to go along with the written material. Another would be for portable radios. Recommended manufactures and models. Issues with using a portable radio in a mobile setting, speaker microphones, heat sets, battery types, battery eliminators, cable adapters from the portable radio to mobile antenna. Again some sample photos. Repeater operation. What are they used for. What specific channels are reserved for them. Explain why there are two frequencies used and in general how this is programed in to the radio. Explain what a "PL" tone is used for and why it's typically required. The how to's should be kept at a low simple technical level. The idea is to help somebody setup a functional radio installation without getting mired in a lot of theory. After the system is up and running there is plenty of time and people who can provide additional info for those that have the interest.

Around by me there seems to be more business use of the frequencies than anything else. Mainly what I hear are the cheap "bubble pack" FRS radios. They're easy to identify due to the funny "Roger Beeps" you hear. FRS is legal for business use as far as I know. Some local retail and manufacturing business, and typically during the day the cleaning crews at the nearby hotels use them. I hear very little personal or family use however. When I do it's mostly after Xmas with kids and lasts for a few days until the novelty wears off and or the batteries die.

I picked up 4 Kenwood TK-370G-1 radios off of eBay and some Ham swaps for a decent price if you look around. I've paid as little as $15 to around $40. You will need a charger and battery for most of the used radios. Most of the radios come with the antenna. Make sure you get the type 1 radio! There are several different versions covering sections of the 400 to 470 MHz range. The link below is the PDF version of the Kenwood brochure with the details for the radios and accessories. https://5.imimg.com/data5/TT/AN/AB/SELLER-3451103/kenwood-tk-270g.pdf Note the radio will do wide and narrow band. By removing a diode inside of the radio, covered in the service manual, then checking the option in the programming software you can enable front panel programming. It's a pain to program the radio this way but possible. I haven't mod'ed my radios since I would rather do the programming through the computer anyway. The radio has Part 95A certification so you're legal on GMRS. https://fccid.io/ALH29473110 The stated range for the radio is 450 to 470 Mhz. However the radio will function down to about 440 MHz which covers the Ham simplex and repeater sections of the band that you're most likely interested in using anyway. I have one sitting on my desk here at work right now scanning the GMRS/FRS - local mall security and some Ham repeaters frequencies. In fact I was monitoring a couple of Hams talking about the snow we're getting, on the GMARC repeater on top of the Renascence Center on the river front here in Detroit. That's about 14 to 15 miles from where I'm at. As others have pointed out it is legal to use Part 90 radios on the Ham bands. To simulate a VFO I programmed a bunch of channels with 25KHz spacing. The channel names were things like 445-200, 445-225 etc. With 128 channels I had enough for the GMRS/FRS, some Ham repeaters and 20 to 30 Ham band simplex frequencies. The ARRL band plans shows the simplex section frequencies over the 442 - 445 MHz range. The repeater sections are 442-445 and 447-450 MHz. The software to program the radio isn't hard to find and you can use the cheap "Baofeng" type USB to serial programming cable. The software will complain if you enter a frequency outside of the stated range but will accept it if you click OK. Good luck with passing your Tech Class license test!!!

The other advantage is the radio can run at high power to give the best signal strength at the receiver, but TDMA means the radio is only transmitting for half the time. That means the radio should be running an average of half of the continuous transmit power, cooler operation and longer battery life. Here pretty much hoping DMR wins due to the dual timeslot tdma, which allows for two concurrent voice calls without requiring additional frequency space...

Great. The service manual came in handy for me. I got two identical dead hand held radios off eBay. Swapped parts around and got one functional. Used the service manual with the diagrams to identify the failed parts and their Kenwood part numbers. Now I can order them and get the second radio fixed. You never know what you may need the documentation for at some point. One other thing I do myself is look for the radio programming software. If I can't get it then the radio would be nothing more than a paper weight and not buy it. I wouldn't send it to a shop to have it programmed. I end up modifying the code plugs from time to time and have different ones depending on what I plan to do with the radio at the moment. I hear too much about Motorola radios and how they handle the programming from a friend who is a radio tech for a local city transportation department. Then the licensing costs for the radio programming software from another friend and his Mototurbo digital radio. I have another friend looking at some used Motorola P25 radios on eBay to use simply as a scanner for public safety monitoring. He says its cheaper than some scanners he looked at. I at least have had good luck getting the Kenwood stuff. Wish you luck and hope the project works out well. On occasions I've felt a radio would work better if it bounced off the wall a few times. 8-\

Everybody has their favorite digital mode. There are enough of them, D-Start, DMR, P25, NXDN and Yeasu's System Fusion to name a few. The fly in the ointment is which "standard" will be the majority of people end up using? Bet wrong and you end up with a radio with dwindling support. So far I haven't seen, or know about, a small hand held radio that offers more that one digital mode. Thus if you use more that one mode you end up with a separate radio just for it. The next issue depends on the digital mode. While radio to radio contacts are basically straight forward going through a repeater is not. The problem is some digital modes may not be compatible with old analog repeaters. The old analog repeater has to be replace at the owners expense with digital compatible equipment. One of the attractions of digital modes is the ability to link repeaters together over the Internet using various VOIP protocols. That requires access to a high speed Internet connection and a sizable infrastructure to handle the VOIP packet routing etc. like routers and gateways, Then there is the need to register to get you own unique ID so your radio can be identified within the digital network and the VOIP traffic routed to it. Digital modes are a lot of fun and have their advantages. One just has to understand what maybe involved and plan accordingly. 8-))

Many USB to serial cables use a chip manufactured by a company called "Prolific" inside. The chip is a popular one so it didn't take long for it to get cloned. The cloned chips were cheaper than the official one. To combat the spread of the cloned chips the company wrote code into their driver to detect the clones and refuse to work with them. The fix to get cables using the cloned chips to work required finding an older version of the driver before the detection code was added. Your other choice is to get a cable using a real Prolific USB to serial chip or the other type using a FTDI type chip in it. https://www.ftdichip.com/USB.html Trying to use a cable with the cloned chip the driver appears to install OK but you get error messages when you use it with the newer drivers. Note that some Chinese radios use the USB to Baofeng type plug, but it's a pass through cable only. The USB to serial chip is built into the radio. My D878UV is like this. Using the Baofeng type USB to serial cable results in connection fail and other error messages. I have to use the specific cable the radio shipped with so its packed away and labeled for use with that radio only. You can buy the USB to serial cables online. The one I have was sold by R and L Electronics in Ohio. I've used it several times to test a code plug for for my TK-2170, the VHF version of your UHF TK-3170 radio. It works fine on that radio and some other ones I have. Used it on both Windows 7 and Windows 10. I didn't do anything special, just plugged it in and let Windows install the driver. http://www.randl.com/shop/catalog/product_info.php?products_id=71426&osCsid=h5bd4ajsq8bnulahcnmjsa27i6 As long as its the same manufacture as the one I got, didn't switch suppliers, it should work. Mine has "Baofeng" on the fat end that plugs into the computer's USB port. If you look around on the Internet you can find PDF copies of the radio user guide and service manuals. Useful to have. Also if you get the FCC ID off the back of the radio you can search the FCC database where you will find the test reports and the FCC grant, Part 90, 95 etc. for example, the radio is certified. https://fccid.io/

You can down load the Kenwood programming software for your radio from the location below: http://www.radioscanner.ru/files/kenwood/file8416/ The download link is near the top of the page. The file you want is "kpg101d.zip" The zip file should also have the license key you need to enable the software install. I have it running on Win 10 Home. I used this software to load a test code plug in to a used TK-2170 I picked up. The radio uses the Baofeng type programming cables. If you buy one make sure it doesn't have a fake "Prolific" serial to USB chip in it. This site has the info about the cables: http://www.miklor.com/COM/UV_GettingStarted.php Sooner or later you are going to want to make changes or load the code plug up into another TK-3170. No point in paying somebody when you can do it yourself.

I wouldn't recommend doing this. The signals on the ribbon cable are very likely logic signals, some anyway, that have sharp rise and fall times thus a high frequency content. Extending the ribbon cable would be the equivalent of a transmission line. If the line was not terminated in the proper impedance at each end then you get reflections. Those appear as high frequency ringing on the logic level transition edges. The voltages can ring above the supply and below ground which can result in damage to the chips on the boards if they exceed the max spec values. Additionally the ringing will look like extra logic transitions further confusing the logic on the boards. Once in my younger days I tried to use the expansion slot on the back of my then new TRS-80, it ran between 2 to 3 MHz, using a 2 to 3 foot long un-terminated ribbon cable to the solder less breadboard. I wanted to try experimenting with some computer controlled hardware. The computer wouldn't even boot to the built-in BASIC interpreter until I removed the cable. Lucky nothing was damaged. Lesson learned.

Yeah, I know about the software bugs with the D878UV. Hardware wise it's a nice radio. At least the front end seems better at rejecting out of band or off frequency signals compared to the other cheap Chinese radios I have. The downfall is the firmware and the customer programming software. If you look about every 1 to 3 months they come out with a new version of both ever since the radio was first released. They fix something in one version, then it's broken in the next. I don't understand why when they fix a bug it doesn't stay fixed in later releases. The last one, V1.17, that just came out a few weeks ago I just sent off another bug report about a couple of things that don't work I stumbled a cross or just plain annoying until they get fixed. Now by contrast my TH-D74A has only a few updates and when the bugs get fixed they stay that way. Yes its an expensive radio but you get what you pay for too.

The site below has some good info on the Anytone, Alinco and Btech DMR radios. http://members.optuszoo.com.au/jason.reilly1/868mods.htm Oh, mode 00014, the password is "878#" typed in without the quote marks.

Actually going to a lower loss line could make the SWR worse as seen from the radio end. The reason why is the energy reflected from the antenna back to the radio is attenuated less, more reflected power, that would otherwise be adsorbed by the feed line. The SWR can be calculated using forward and reflected power using the formula below: SWR = (1+sqr(Pref/Pfwd))/(1-sqr(Pref/Pfwd)) Where "sqr()" is the square root of the value inside of the "()". And "Pfwd" is the measured forward power going to the antenna while "Pref" is the power being reflected by the antenna miss-match back to the radio.

I would NOT recommend using PL-259 and SO-239 connectors at UHF. They are not "constant" 50 ohm impedance. Depending on how many you have and where in the system they do tend to degrade the SWR. Good connectors to use at UHF are "N" type, BNC, mini RG8, SMA are the more common ones. Many mobile and base radios use an SO-239 on the back so you can't do much about it. The better ones use the "N" type. Where you see SO-239's used look at the inside of the connector. If you see what looks like thin a web between the outside of the center pin and the inside of the outer shell, like the spokes on a wheel, cause less of a problem compared to the solid filled ones. This is done to improve the impedance of the connector to bring it closer to the desired 50 ohms. The antenna ground radials, if required, should be around 1/4 wave length long, approximately 6 inches long, and could be bent downward at a 45 degree angle from the horizontal. Some of the antennas that claim not to require a ground plain are a "J-Pole" internally. These antennas should have several turns of the coax located right at the base to decouple it from the outside of the coax shield. If this isn't done then RF current flows on the outside screwing up the antenna TX and RX pattern, RF getting into the radio resulting in TX audio distortion and in addition to causing weird SWR problems. If your SWR is 1.3 to 1.5 there may not be much to gain by improving it to the ideal 1 other than to make one feel better. Most radios are designed to tolerate SWR's up to 2 at full power anyway.

Maybe I should take another look at the 629's.

I was looking at the 628’s, not the 629’s, originally. Now I’m not sure. I just purchased a Kenwood TK-2000 package with programming cable and software new on eBay for $50. I was going to experiment using that radio and a Baofeng BF-888 with an MFJ-916 duplexer to make a simple low power VHF/UHF cross band repeater.

Which ones have you used? I've been looking at reviews on these on and off for a while and I'm not likening the comments I've read, to many negative ones. Yes I've seen the comments about the first half second being cut off. That's happen to me with radios with VOX operation or a VOX headset so seeing it mentioned with the controller isn't a concern. All it means is the electronics needs enough audio signal level to detect long enough to ensure somebody is really talking so the radio TX isn't tripped randomly. What gets me are reports about out and out failures or the audio is fine for a while then for no reason is distorted. Some reports the controller will no longer switch the TX radio on etc. One guy said power cycling his would fix the audio distortion problem on his for a short while then mess up again. Then there are people like you who say they have no issues. From those that don't report issues to the frequent ones who do I begin to question the manufactures quality control.

If you want to do an "in-band" repeater you will need two radios, a duplexer and a controller as the main components. You can buy a cheap UHF duplexer at this site. If you supply the two frequencies they will tune the filter at no extra cost. Also don't forget to get any N to whatever RF adapter you will need to connect to the radios and the antenna. www.409shop.com/409shop_shopcat.php?&usercat=4942 If you want to know how well these cheap Chinese duplexers work a guy did some testing on one here. http://www.repeater-builder.com/antenna/pdf/chinese-mobile-duplexer-measurements.pdf Then use a simple repeater controller like this one. https://radio-tone.com/product/rt-crc1-repater-controller-full-duplex/ I see ad's for the "Surecom" controllers but have read a lot of bad or poor reviews. The one above seems to be OK. Also don't forget to get the right radio interface cables with it.

Or do a "parrot" repeater. This is where you TX and the controller will record the message. When you're done it then re-transmits the message. This of course slows down the communication, and some find them annoying to use, but are simple to setup using one radio and fairly cheap. There are several YouTube videos where a guy did this putting the guts in an ammo can with a battery and charge controller connected to a used solar panel. He used the metal ammo can for the ground plane required by the antenna. Stuck it on a mountain top in a very remote area. Had it there for about a year or so running before having to service it. The repeater controller he used should be like this one. https://www.argentdata.com/catalog/product_info.php?products_id=98

Also you can't crossband between the Amateur Radio service to GMRS or MURS either.

What does the local terrain look like around the site? Another point to consider is very high gain vertical antennas have a narrow radiation pattern perpendicular to the antenna. General reciprocity antenna theory says the RX and TX patterns should be similar. Anyone close in will have a hard time getting into a repeater like this since the antenna is deaf if you're not in the RX pattern. Commercial broadcasters and some repeater installations use antennas designed so that the narrow radiation pattern is not perpendicular to the antenna but has a small "down tilt" angle of several degrees to compensate some what for this condition. A lower gain antenna has a wider RX and TX pattern perpendicular to the antenna. The gain fall off is less severe. That's why you read about people claiming that a simple 1/4 wave on UHF gave them better results in hilly terrain verses using a high gain antenna where other stations are at different elevations relative to each other.

Oh, one more point. Be careful what version of a radio model you buy used! For example the Kenwood TK-370's and TK-370G's come in several variations that cover different ranges in the UHF band. You want to pick one that covers 462 MHz to 467 MHz. There are 4 versions of the 370's and 370G's. 450 to 470 470 to 490 490 to 512 403 to 430 If you get a 370 you want the "type 1". The ID tag, on the back of the radio on the aluminum chassis under the battery, should show "TK-370-1" or "TK-370G-1" on it. The type 1 is the 450 to 470 range. The radio will also program down in to the Ham 70 cm band to around 440 MHz. The Kenwood software will complain its out of range but will let you do it anyway. The radio will work there which is convenient for those dual licensed for Ham and GMRS. 8-)

I agree. I've picked up several Kenwood TK-370's (wide band 32 channel, repeater operation, 4 watts), also have several TK-370G's (wide/narrow band 128 channel, repeater operation, 4 watts). Both have part 90 and 95 certification. If you search and wait you can get one at a fair price on eBay. The programming software is easy to find on-line. These radios use the same exact cheap "Baofeng" programming cables. Just make sure the one you get doesn't have the cloned USB to serial chip in it, the newer windows drivers don't work with them. Parts for these radios are easy to find. You can get the drop-in battery chargers, battery packs, antennas etc. The TK-370G uses the reverse SMA antennas. The TK-370 however uses a Motorola MX type but you can get a MX to BNC adapter to use an external antenna. If you buy a used radio be sure you can get the programming software and cable for it! Just about every business band radio has to be setup using the software because there is no "front panel programming" typically, at least on the hand held radios.

What is the source you got the graphs from and how were the tests done?

Military man pack radios I haven't used and don't really know much about them. I would suggest you search around the Internet for a group(s) that specialize in that kind of equipment for info.