Lscott

I’m going to guess the coordinators use some software tools to estimate area coverage and signal levels to figure out potential interference to co-channel users. Are these publicly available, free to use, or expensive proprietary software?

Well at least a few people figured out CB radio is used for “communications” not to generate attention grabbing noise, make a fashion statement or stroke one’s ego by being the channel king.

I wonder how long it will take before you see these showing up on eBay at a cheap price.

Thanks. That was a very good detailed explanation. Tower rental costs isn’t something I see mentioned hardly at all on these forums. Hams get spoiled since a lot of them get freebie, or nearly so, space on buildings etc. Everyone else ends up having to pay.

Ok. The modified radiation pattern due to the tower acting as a passive reflector makes sense. Another group member here has done it on a multi bay vertical where the mast was the reflector. I modeled it using EZNEC and it does work. There was noticeably higher signal strength on the side opposite the mast. It wasn’t a huge difference however. I get the extra revenue from more antennas mounted on the tower, and using it the shield one antenna from another, why you see a lot on side arms. I just thought it a bit odd nothing was mounted on the top spot on a number I’ve seen.

Here is a question. I've noticed on some towers than none of the antennas extend above the top of the structure, all are mounted on side arms. Is that done to stay under the permitted height of the tower?

The new DHS bureau of disinformation will put an end to that idea.

It would nice if they did. This topic should be split off into a separate thread. However some of the benefits might be lost along the way, increased channel capacity and lower battery drain. People are confused enough trying to figure out repeaters, offsets and tones. Now you want them to understand talk-groups, color codes and time slots? I suspect if it ever does get approved it will look more like the DMR446 license free service you see in Europe as a DMR tier 1 service. There the radios transmit on both time slots I believe from a few websites I've been too looking for info. The later might be country specific. So much for added channel capacity and lower average TX power savings. What they do for talk-groups I'm not sure. https://kenwoodcommunications.co.uk/files/file/comms/uk/pmr446/PMR446-White-Paper-V6_18AUG2016_JT_KB.pdf They also have dPMR446 which uses FDMA, which is very similar to NXDN. Note they have several different codecs that can be used. You can find the Chinese dPMR radios, most are really DMR (TDMA) based, while a few are FDMA but use some Chinese specific version of a codec that is not compatible with the AMBE+2 you typically see in NXDN, P25 and DMR radios from the major manufactures. https://en.wikipedia.org/wiki/Digital_private_mobile_radio Confused? Yes they have three different modes used on their license free service, the equivalent to our FRS radios. It seems to work for them so I don't see why it won't here.

You can get the optional spring and swap out the lower section in case you forget for that antenna. I recommended that for a buddy at work and he installed it.

You can no longer use voice inversion on GMRS. That was one of the changes made in the 2017/2018 rule updates I believe.

I believe Motorola’s patent on MDC has expired. That would mean it’s no longer even a “proprietary” signaling system. The patents are listed at the end of the below article on Wikipedia. The technical details are known how it functions. https://en.wikipedia.org/wiki/MDC-1200 Several of my Kenwood commercial radios have it. For example the TK-3360. https://pdfs.kenwoodproducts.com/16/TK-2360&3360Brochure.pdf The radio can be easily programmed to work on GMRS, however it’s only certified for Part 90 so it’s not strictly legal to use except on Part 90 and the Ham 70cm band. Personally I’m more interested in seeing the FCC to allow some form of digital voice to be used. I think people favor DMR. If they allow NXDN my NX-300’s are already certified for Part 95A. I can use them on GMRS FM currently. https://comms.kenwood.com/common/pdf/download/301_NX200-300.pdf NX-300 FCC Grant - 1.pdf

Ham radio in general is more permissive in what technologies are used for communications. The principal limitation is on bandwidth, transmissions have to fit into allowed emission masks. Also you can’t use codes or encryption meant to obscure or hide the contents of the communications. There is an exception for satellite control ground stations for obvious reasons. The recent rule changes for GMRS in 2017, effective in 2018, encryption is now prohibited on GMRS, including the old voice inversion methods. You’ll likely find this on the older, pre rule change, radios but can no longer be used. So even though modes such as NXDN on Ham, for example, are proprietary they are “published” so anyone can receive the signals and don’t count as encryption thus legal to use. The same would apply to many other signaling systems currently in use. If one wants to design a new signaling system, fine, but the technical details have to be publicly available to any interested party. On GMRS you can use modes other than FM. There are several that are permitted, such as SSB, J3E. Not likely to encounter that one but it is listed as a legal mode. https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-E/section-95.1771 https://repeater-builder.com/tech-info/pdfs/fcc-emissions.pdf So I would recommend looking over the rules to see EXACTLY what is permitted first, then examine if a particular mode/signaling system is allowed per the FCC emission masks. Then decide if its an allowed emission does it fall under the prohibition of “codes” meant to hide or obscure the communications.

That's an interesting point. If I remember right some time ago a guy wanted to setup several GMRS repeaters around his area and CHARGE access fees to use them. Being there are only 8 repeater pair frequencies that consumed a lot of "public resources" for his personnel monetary benefit at every one else's expense.

I have a buddy who picked up one for 800MHz. Cost him $75 at a swap. The use was to monitor the local PD which was on a trunked system. He managed to find the software for it and the one to generate a system key file he said was necessary to get it to monitor a trunked system. The software is out there. Might be sort of hard to find.

They do cause interference. I design high frequency high power switching power supplies for a living. Trying to shield those things is far harder than you think. There are various ways noise can escape from them each requiring their own technique to correct it. That costs money the manufacturer won’t spend on the cheap models, which might be OK for consumer grade use around broadcast radios. However communications grade radios are a lot more sensitive and not all switching power supplies are suitable to use around them. I have a few on the shelf at home I can’t use around my radios for that reason. I don’t care what FCC labels are on them.

Very true. Those USB power adapters likely use some type of switching power supply, which is a huge noise generator, with very little filtering on the output. This is another point too. Most of your 120VAC to 13.8VDC power supplies are also using a switching type design. The ones used for powering mobile radios are specifically designed with more shielding and noise filtering. Some people have purchased cheap ones only to discover later the noise generated wipes out the signals they are trying to receive. There is a reason why the ones designed for two way radios likely cost more so a cheaply priced one may not be the best deal.

As pointed out already USB is only 5 VDC. You can get a DC to DC converter however there is a second problem. Most USB adapters/plugs can only supply 1 amp max. A 5 watt radio will likely draw up to 2 amps at the battery terminals on transmit. The total power drain on the low voltage side of the DC to DC converter will be higher due to the lower input voltage, power in = power out + converter losses, which will exceed the rating for the USB outlet.

Try this forum group. https://groups.io/g/KenwoodRSS/topics You will likely have to register to get access. Once you do then send a message to "Garrett Ramsey". He has been VERY helpful to many people with questions or issues with locked radios. He has helped me a few times. Jan 18 #304

I'm sure a few people here are going to the Hamvention next month. How many are looking at using some kind of digital communications and which specific mode(s)? That would be either using a repeater or just simplex. I have a number of radios that cover the usual ones except for System Fusion so far. I'm assuming the most popular ones are D-Star, System Fusion and DMR. Anyone planing on using P25 or NXDN? I'm thinking about taking several radios but trying to decide which ones.

Makes sense to me. I wonder if a packet network would be allowed? I’m thinking about packet routing if that would be considered a store and forward operation.

Yes, there are some very specific restrictions on data transmissions on GMRS/FRS. I posted about that in another thread about non-removable antennas. However it’s specifically allowed on MURS. Of course the rules also don’t allow repeater operation so that question can’t even come up, and limited to 2 watts. But data transmission is allowed on MURS. Apparently a variety is mentioned in the rules. MURS was created as a Multi Use Radio Service, not primarily, or strictly used, for voice communications. https://www.law.cornell.edu/cfr/text/47/95.2731 While APRS can’t be relayed through a repeater it can still be used on a local basis, like for example search and rescue work, in a limited geographic area using simplex communications. At least that’s how I see it.

I haven’t really used APRS so could you expand on what you see as an issue with using it on MURS, or GMRS/FRS?

http://arrl.net/ ARRL -> Amateur Radio Relay League That's how it was done in the very old days of spark gap transmitters that had very limited range. Messages were relayed from station to station across the country. What is old is now new again. It continues to be done as a message passing protocol. The key is getting a system where the format is consistent and EVERYONE uses the same procedures to pass message traffic. Otherwise it ends up being nothing but a mess.

I looked at the photo of one on the web site. The antennas are obviously molded in with the case. https://www.garmin.com/en-US/p/576031

Humm... There does seem to be an interesting twist to what is allowed for antennas on GMRS radios. It's not specifically related to operation on FRS channels. However it has to do with data transmission which likely most radios don't do. 95.1787(a)4 https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-E/section-95.1787 So if you are looking at a GMRS radio that can send some kind of digital data, lets say GPS location, then you will likely find the antenna is non removable. So yes, my prior comment in general was incorrect, but after looking at the rules a rather narrow exception to allow removable antennas seems to exist. People looking to buy a GMRS radio with built in GPS data transmission for hiking/camping need to watch-out for this for example.