Lscott

Here is a question I haven't seen talked about. On many of the commercial grade digital radios they can be operated in analog only, digital only, or in mix mode. The later would have the radio programmed to receive in either analog or digital on a given frequency while automatically detecting which mode is in use and demodulating the signal as necessary. The transmit mode is usually set for either analog or digital exclusively. I don't have any of my radios programmed for mix mode. Other than monitoring a frequency for activity has anyone else found it beneficial?

I'll take your word for it. You have the real world experience to back it up. Was there anything that was, or could be done, to mitigate the interference issues?

Yeah, should get back on topic.

I forgot to mention there are also problems with "clock drift" of the internal oscillators in digital radios and DMR also has to deal with range limitations due to slot timing too. See page 110 section 10.1.4, and page 113 sections 10.2.3.1.2 through 10.2.3.2.3 in the following link. https://www.etsi.org/deliver/etsi_ts/102300_102399/10236101/02.02.01_60/ts_10236101v020201p.pdf

This is encouraging, somewhat back on the thread's topic and people expressing some interesting ideas and opinions. Some of the issues, with at least DMR, is the proliferation of mainly Chinese radios, cheap and not so cheap. The cheap ones tend to give users a poor impression of the mode's performance. The commercial radios are much better, but of course more expensive. IMHO the issue with DMR causing interference to analog users I believe can be traced to poor receiver design and channel separation. For example the common bandwidth quoted for DMR is 6.25KHz "equivalent" which is not the same as a true 6.25KHz signal. DMR is in fact a 12.5KHz signal, and due to TDMA, two voice streams can occupy the channel, that's the equivalent part. Some radios cheap out by using 25KHz IF filters in the radio while limiting the FM deviation to 2.5KHz to meet the FCC's 12.5KHz occupied bandwidth. Locating a adjacent transmitter closely to such a receiver will result in the DMR signal spilling over in to part of the pass band of the affected receiver.

Somebody with far more experience than me would need to VERY carefully write up a petition for submission. I think it's been tried before. I'm guessing any chance of success in rule modifications are those that requires the least work on the part of the FCC and not going overboard on the requested changes. The last part I think is key to the whole thing. Keep it modest and reasonable.

That is a big consideration. The proposal to use the low power channels, 8-14, was an attempt to mitigate the issue. I suspect most GMRS radios don't even include the low power narrow channels, and if they do most users, I suspect, ignore them anyway. This way to side step any FCC objections to new spectrum allocations.

That's very unlikely to happen for several reasons. 1. The Hams will vigorously defend their spectrum from getting "pilfered" by another service. If they did take any spectrum the FCC would likely auction it off for money. 2. It would require some major revisions to the GMRS rules and spectrum management, not to mention mucking up the unified frequency allocations between GMRS and FRS. 3. The primary user of the 70cm is the government. Hams are only secondary users.

Well that's what the FCC had envisioned the service's main use. However as any casual member of this forum sees it has evolved more towards a hobby use. I guess there is nothing wrong with that, but the FCC would be quick to point out that wasn't the original intent. That was mentioned in the initial comments. The purpose of the document is to get people thinking about it and to at least consider what the FCC might realistically consider. Start small and when you gain some ground push a little further. This plays into the topic of this thread. There are a lot of digital modes in use on the Hams bands. While that might be a good thing it is also a negative, too many modes. For the general non-technical public picking once digital mode for GMRS I think is the way to go. With the experience of multiple modes on the Hams bands I think we, Hams, can offer some recommendations that make sense and fit the GMRS service. There is a lot of equipment out there and modes in use to choose from.

Well there could be a way. People need to consider the possibility and how it could be done. I can think of one way where most of the objections are addressed. The use of digital voice might not be appropriate in some situations and advantageous in others. GMRS Digital Voice - 20221011.pdf

To get back on topic has anyone heard of or used dPMR here in the US? It's very similar to NXDN, but uses a different protocol, and is used in Europe. https://en.wikipedia.org/wiki/Digital_private_mobile_radio The license free service they have over there, like our old FRS rules, allows them to use narrow band FM, DMR or dPMR, at at 0.5 watts. https://kenwoodcommunications.co.uk/files/file/comms/uk/pmr446/PMR446-White-Paper-V6_18AUG2016_JT_KB.pdf Makes one wonder why the FCC is dragging their feet here over allowing digital voice on GMRS. Also dPMR is allowed for their equivalent of our LMR business service, Part 90, at higher power. https://dpmrassociation.org/dPMR-a-brief-overview.html There is another issue I stumbled across with cheap Chinese digital radios. Apparently they have a habit of using Chinese codecs in many of them that are NOT compatible with the usual AMBE+2 ones that seems to be the standard in many of the higher tier radios from the big name manufactures. https://radiosification.blogspot.com/2019/01/dpmr-vocoders.html

Unless I'm miss reading the waterfall display the frequency is 442.775 MHz which is in the Ham 70cm band. That's not GMRS.

I typically use the handheld radios. A favorite model is the TK-3170 or TK-3173. https://forums.mygmrs.com/gallery/image/263-tk-3170jpg/ A number of those have Part 95 certification. If you don’t care about that there are more models to choose from. If I want to operate GMRS mobile I just use them with an external antenna. The radios also are programmed with Ham frequencies too. https://forums.mygmrs.com/gallery/image/249-934916052_radiocollectionjpg/ I have just one Kenwood mobile which I don’t currently use. https://forums.mygmrs.com/gallery/image/250-nx-820ghjpg/

I think that qualifies them as being cheap, stupid and dumb.

I hear ya. These were really cheap to build too. https://forums.mygmrs.com/gallery/image/264-uhf-antennasjpg/

I've pealed off the Mylar on a bunch of magnet mounts. A good replacement is using some of the aluminum duck tape you can buy at the home improvement store. It sticks like crazy and is easy to trim off using a sharp blade. Also being aluminum it helps couple the antenna to the metal roof.

I think more public service and first responders are going with NXDN since the cost of the SU, Subscriber Units as the radios are called, seem to be cheaper than the P25 stuff, judging from what I see sold used on eBay where I get my stuff. For P25 I think a lot of that is up on 700/800 MHz tied in to large regional trunking systems, and those tend to be encrypted anyway. If you don't need access to those systems I don't see why you need P25. I'm not very knowledgeable on the public safety stuff so I could be way off base on this.

What kind of radio are you using? This could be important. Also have you tried a different model radio and see if you get the same results? You could be experiencing an "image response" where the signal isn't really on the frequency you think it is. I have a nearly full scale signal on my Ham HT, old TH-G71A dual band, set to receive on GMRS/FRS channel 7. NO other radio I have shows anything there when set for the same channel/frequency. https://en.wikipedia.org/wiki/Image_response https://www.electronics-notes.com/articles/radio/superheterodyne-receiver/image.php

Used P25 radios are expensive. I can buy 2 or 3 NXDN radios for what some people want for just 1 P25 radio. I'm still looking for an affordable TK-5220 VHF P25. I have 2 of the UHF TK-5320's and 1 of the TK-5220's now that didn't break the bank. In general LMR VHF radios are selling for more than the UHF models. https://forums.mygmrs.com/gallery/image/254-tk-5320-1jpg/

Another local wide area coverage GMRS repeater went up a short while back and was upgraded to a Quantar UHF repeater the last few weeks. My understanding is these are rock solid but finding replacement parts could be difficult. https://www.repeater-builder.com/motorola/quantar/pdfs/quantar-v-u-8-brochure.pdf Most of the traffic seems to be Hams holding GMRS licenses. I recognize the voices from another local Ham 70cm machine. I hope they don't crowd out the GMRS only users. https://mygmrs.com/repeater/6646

I would be right in the intersection of all of the circles. I haven't used CB in years. The last time was when I had to do a lot of business travel for the company and drove to customer sites. The van, I had at the time, looked like something out of the X-Files with the antennas on it. It was fun hearing the truckers on 19 make comments about it as I drove by. I even had a guy driving in circles around it in a parking lot as I came out of a carry out pizza joint one day. Turned out it was a fellow Ham. He couldn't figure out what the small square horizontal loop was for. I explained it was for 2 meter sideband. At the time I had a Icom IC-706MKIIG rig in the van which did FM,AM and sideband on 6M, 2M and 70cm. https://www.icomamerica.com/en/products/amateur/hf/706/specifications.aspx https://www.m2inc.com/FG2MHOLOOP

Just like people who buy an expensive luxury vehicle and when it comes time to replace the tires buy nearly the cheapest ones they can find. Life is full of examples of this sort of things. Hams are no different.

You find out real quick just how serious people are about it when the repeater owner starts asking for money from the users to pay for it all. Not surprisingly most of the interest fades fast at that point.

Cool. And that’s enhanced by the skill of the operator.?