Lscott

I'm not so sure of the reception ability of the D878UV design. I had my first generation D878 sitting on a desk next to my Kenwood TK-D340U. https://comms.kenwood.com/common/pdf/download/DMR_TK-D240V_D340U_K_letter_1124.pdf Both were monitoring the output of a local DMR repeater. On multiple occasions the Kenwood would decode audio while the D878 just light up the green RX LED and nothing was decoded. I'm doubting the ability of the D878 to reliability decode DMR traffic now. The best feature of the D878 however is the digital monitor mode. You have no idea what slot, color code, talk group and user ID is being used, well the digital monitor mode shows it all. Unfortunately the higher end commercial DMR radios can't do it. I have a MARS/CAP modded TK-D74A. The radio is a beast. It's the fastest scanning radio I have, something like over 20 plus channels per second. I've only used mine maybe a few times. Other than the D578 it's the only other radio I have than can run digital voice on the 1.25 meter band. With the prices these are selling for used it's like own a brick of gold. One odd thing is nobody in North American sold a soft case for it. I even contacted the US based Kenwood tech support and they confirmed it. Nobody could explain why. I had to order one from a Ham radio dealer in the UK and shipped it by airmail here.

You can use directional antennas, or a bit more power with an “eggbeater” type for TX and RX. The way they are designed is the radiation pattern is circularly polarized and directed up and out to the horizon, thus no tracking required. http://146970.com/PDFs/Antenna Eggbeater-Revisited-English.pdf

I don’t like the one I have. It was a freebie. Had nothing but problems trying to program it. Half the time or more the communications between the PC and radio fails so you can’t reprogram the radio. After a few tries I tossed it in a storage bin. Haven’t touched in a couple of years.

I wouldn't mind having one myself. I've been on the look out for a good deal on one. For $150 and no slugs I can get one that's beat to crap, or for $250 to $300 and still no slugs I can get a nice one in very good condition. Don't forget you an buy them with different connectors. They can be swapped but you're better off getting it with the ones you want. Also the slugs aren't cheap either.

Well you are the best judge of which connector type will suite your needs the best. Don't forget you may at some point want to use the antenna with another radio, such as a mobile, so you'll likely will need some adapters sooner or later anyway.

You have a choice for the RF connector. I wouldn't recommend the SO-239 unless you absolutely need it. Personally I prefer the BNC. I can easily find adapters from BNC to just about anything, and BNC terminated patch cables of various lengths are easy to find. Plus the BNC is a constant 50 ohm type so it's very unlikely to cause any kind of noticeable SWR issues. The down side is it isn't water proof. If the antenna is used out doors where it's going to get wet you might want the "N" type connector, which is pretty much water proof.

I would recommend the Slim-Jim. It doesn't require a ground plane like a 5/8 wave antenna would. It's also good for portable operation like camp sites etc. When not needed it's easy to roll up and stick in a drawer. If you get the dual band version it works on VHF MURS and the UHF GMRS channels. https://n9taxlabs.com/shop/ols/products/dual-band-murs-gmrs-standard-antenna

This should get some interesting responses. People talk about their first radio or their favorite one. In this case which one you disliked the most you wasted money buying? This could be more useful for newbies.

It's 2.6:1 on GMRS? That's high. I'm guessing you mean 1.6:1. The antenna is a good wide band design, but it's a bit sensitive to the mounting location. Being a 5/8 wave it needs a good ground plane.

As @BoxCar mentioned it's yes and no. Some antennas might work just fine even if the manufacture's specifications don't cover the frequency range. You'll need to test it. I have an old, like 20 years, dual band Comet antenna that works great on both Ham bands, MURS and GMRS. Unfortunately they don't make it any more. I had purchased two at the time. One I used strictly indoors, never saw the outside and looks like new. If the one I have on the vehicle ever fails completely or gets destroyed I have a back up. I did an SWR scan using a RigExpert AA-1000 antenna analyzer. https://rigexpert.com/products/antenna-analyzers/aa-1000/ I was curious to see how it performed verses the manufacturer's spec's. See the attached files. The scans are the antenna as mounted on my old Jeep's roof rack cross bar. CA-2x4MB Manual.pdf

That makes more sense. ?

The continuous carrier bit is confusing. One could interpret that as 100 percent duty cycle or would that be CW type communications using Morse code? I'm guessing it's the 100 percent duty cycle one. The interference part seems to be ignored. I can't see how how a remote doorbell- pager will monitor for channel activity without the incorporation of a BCL, busy channel lockout, function. Same with telemetry systems etc. I think these applications just TX in the blind and screw any other traffic that happens to be there. Anyway MURS, Multi Use Radio Service, is the garbage band for stuff nobody wants elsewhere on VHF.

The FCC rules allows all matter of stuff that's prohibited on GMRS. I don't doubt that some areas may see little use, but that doesn't alter what is authorized. https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-J/section-95.2731 What is notable is I don't see any limitation on the duration of those permitted uses. That would imply they can be used at high duty cycles.

Yes, DMR might make sense for MURS. It's already sort of a catch-all garbage service as it is with people using remote doorbells, wireless data logging devices etc. I doubt DMR would do much more to mess it up than all the other crap that's there now.

You have some valid points. I think the issue with going digital has more to do with improved voice quality than anything else. There is some possible range improvements, likely due to digital voice modes to maintain clear communications until you reach the range limit. As you pointed out the signals propagate the same regardless of mode. I suspect the attraction of digital voice for the average non-technical GMRS user is clarity of the audio signal under conditions where analog FM will sound like crap. It's a better user experience. The issue with how to configure the radio for digital mode(s) can be addressed by restricting the options. For example all compatible radios must use the same time slot, or likely both, the group ID can be fixed (All Call), leaving leaving just the color code as an option. Remember the EU has the dPMR446 license free service. The use of DMR isn't really the only choice. I wish people would get that out of their head and consider the other modes that might be much better, simpler, from a user's view point. There are other digital voice modes requiring less setup, such as the one I just mentioned. I have the programming software for the Kenwood TK-3701D, which is an EU license free analog/PMR446 radio, just to see what it looks like. See attached file for an example of the digital half of the radio memory setup. It's really not that complex, on a par with analog FM. Part of the issue with getting the FCC to consider digital voice mode(s) will be how to fit it into the existing GMRS service given it's current limitations. DMR might not be the best idea regardless of how "popular" it is. People are using it simply because it's readily available with somewhat affordable radios. As some others have pointed out it's already causing problems. Using a different digital voice mode with some sane rule changes that can be fixed IMHO.

The rationale for pushing for digital voice modes has nothing to do with making GMRS an “Amateur Radio Lite” service. In fringe areas FM doesn’t result in clear reliable communications. Having the option to use digital voice, and the documented better received audio signal quality in conditions where FM signal quality is poor, is the point.

Hypothetically if one didn’t use the amplifier there wouldn’t be the necessity of asking the question.

You might like this idea. GMRS Digital Voice - 20220803.pdf

An in-band repeater you likely need a good cavity duplexer. Tuning one isn't so easy with the inexpensive VNA's since they lack a high dynamic range. The attached files are from my on-line library I keep on the computers and smartphone for quick easy reference. For duplexers this might prove useful. Calculating Required Isolation.pdf 468523097_RepeaterAntennaSystems.pdf Understanding Maintaining and Re-Tuning Antenna Duplexers.pdf

The next thing you're going to want is a good antenna analyzer. There are lots to choose from. Seems the favorite is a VNA, vector network analyzer. Be careful which one you buy. Some are using crappy components, poor PCB layouts and generate poor results. https://nanorfe.com/nanovna-v2.html

This is why the FCC will have to address allowing digital voice on GMRS sooner or later. It's happening with, or without, their official blessing. I would rather see digital voice incorporated officially in the rules, which hopefully will eliminate the chaos that currently exists. It also has to be coupled with some meaningful enforcement actions, at least directed towards the more frequent and flagrant violators. Right now the complaints stem from DMR operation on GMRS. However I'll bet that's not the only digital voice mode you'll find in use on the service. There are plenty of commercial radios very capable of FM and digital modes such as NXDN and P25. I have several of those and some are Part 95 certified. Just can't use the digital half of the radio. Then you have some of the modified Ham gear, MARS/CAP mod's, running D-Star and YSF. A real smorgasbord to sort out. I started a thread a while back about possible Part 95E rule changes to allow digital voice on GMRS. Seems like people don't care since the thread just died from lack of interest. Also it got derailed early on over lecturing about FHSS, which wasn't the point of the thread anyway. Oh well.

Try reading this book. It's written for the average Ham Radio operator so it doesn't get crazy with the math etc. http://www.w3pga.org/Antenna Books/Reflections III.pdf

There is a lot of misinformation and myths surrounding SWR and coax cables. I would recommend reading the book at the following link. http://www.w3pga.org/Antenna Books/Reflections III.pdf