Lscott

You just guaranteed this thread will never end.

My comments are to long to type so read the attached file. As stated in the very first post the idea is what rule changes are required and the probability of of getting the FCC to consider the idea. I have ZERO interest in any lectures about the technical merits. That totally derailed this thread from the beginning and I'm not going there again. I debated even responding to this thread and decided to give it one last try. I make no apology for grammar, punctuation, spelling etc. My aim was trying to get some ideas down. GMRS Digital Voice - 20221011.pdf

Has to be rugged and reliable. If it dies from dropping on a cement floor it’s useless.

You can buy a “cheap” Chinese Radio, CCR, and program it for receive only. Typically the transmit function is disabled by leaving the field for the transmit frequency empty. They come lock to the Ham bands for transmitting, receive isn’t a problem. There is a very simple way to change that using an undocumented command in the programming software and password. I’ve been using a cheap TYT TH-350 tri-band radio as a scanner in the house to monitor local communications. I think it works better than the BTECH model and costs about the same. http://www.randl.com/shop/catalog/product_info.php?cPath=370&products_id=74359 The programming software works reasonably well.

Passwords for Kenwood radios are numeric only.

I was concerned with GMRS specifically. Many of the popular radios I suspected are firmware tweaked versions of the commercial LMR versions. I found a list of some of the popular models for GMRS with their FCC ID's here. https://www.buytwowayradios.com/blog/2018/12/wouxun-radio-fcc-id-and-type-acceptance-chart.html Doing a spot check of the GMRS certified radios the ones I looked at are all 16K0F3E. That's sort of what I expected.

I think that’s why the FCC left the spec’s for the interstitial channels between the repeater main ones at 11K0F3E and 0.5 watts to limit the interference to them. I’m just wondering if the manufacturers are leaving the bandwidth at 16K0F3E on the higher power channels since many of the Chinese GMRS radios are based on either old Part 90 or Ham gear with tweaked firmware to make it legal for Part 95. If the norm for the majority of the radios in use is 16K0F3E the FCC could just tweak the rules and make it official. That leaves a larger guard band between channels that could be employed to advantage for other uses.

I’ve been thinking about an issue, which isn’t important at the moment, where the occupied bandwidth of the signal is a major concern. The FCC spec’s 20K0FE3 as the normal “wide-band” FM signal mode for GMRS. However many people, including myself, have Part 95 certified commercial radios that are spec’ed for 16K0FE3, the old Part 90 rules, we use. Also the vast majority of GMRS repeaters are built using commercial Part 90 gear, which has the slightly narrower emission. Likely wouldn’t even notice the differences on the air. So the question is are the typical radios being specifically manufactured for GMRS are they certified for 20KHz or 16KHz occupied bandwidth? If the later it may make a difference for future proposed changes to the service. Just one less item for the FCC to raise objections over since it helps reduce the interference potential from adjacent channels.

With the rule changes in 2017, effective in 2018, business use of the frequencies is legal so long as they use FRS compliant radios. No call signs are required. Anybody who monitors the simplex channels will likely hear all sorts businesses on the air using them. Just have to deal with it.

With the stopper in place you can't turn it that far. Normally on the Kenwood radios I the radio will generate a warning tone and flash/change color or the LED on unprogrammed channels. When I tried it on this one, with a knob missing the stopper bit, nothing happens like the above. I guess I'll have to screw around with it a bit more. I'm also looking at seeing what changes between the 2 channel Protalk version and the 2 channel LMR code plug versions of the radio. It would be far easier to do all of the editing using the LMR version for all the settings, then switch the ID in the code plug to the Protalk version. Otherwise the software will complain. So far I can get the software to think the LMR code plug is for the Protalk radio but I noticed the free memory count showed "-16", oops. I need to see which byte(s) might control that if any. It might not even matter so long as I can write to the radio.

Well an update on the TK-3200 Protalk. Just got home from work and loaded the hacked code plug in the radio. It seems to work just fine on the local repeater in the area for GMRS so I count this as a success. Now all I have to do is figure out how to use the full 8 channels, at least the selector switch on top has detentes for 8 with a channel stopper after two. Have to think about that a bit.

That's true. I tested a TK-3160 16 channel radio with the 450-490 band split. The radio started beeping around 433MHz, couldn't phase lock. I tried the same thing with a NX-320 with the 450-520 band split and it failed between 442MHz to 443MHz. I'm guessing the wider the band split the harder it is to get the radio to operate outside of it's official specifications. For the used radios I'm buying I try to get only the 400-470MHz band split version. For some models those are nearly, if not, impossible to find.

I've had some success with Kenwood Part 90 radios getting them to work down into the Ham 70cm band. If it will function down to around 440MHz that would be OK since that's where most of the repeaters are located anyway. I'm using the KPG-88D software for the TK-3200. The version I'm using allows wide and narrow band FM. I do the initial editing using the software then save the file. The custom hacking is done with a hex editor. In the attached file you'll see I have the local repeater frequency, RPT-16, and tone entered, and also the simplex frequency for channel 20. The software won't allow different TX and RX frequencies, even from the allowed list, nor split tones. That's what I had to do by hand along with the GMRS frequencies. The software always forces the same tone for ENC and DEC columns, and the same frequency for RX and TX. The attached photo shows what you see when the hacked code plug is loaded into the programming software.

I'm working on hacking a Kenwood TK-3200 2-channel Protalk radio to work on GMRS or Ham. https://www.buytwowayradios.com/kenwood-tk-3200-u2p.html I had a buddy give me three of them for free with charger bases and battery packs. I have a custom hacked code plug, had to use a hex editor, I have to load into a radio for testing later. I need to test if the firmware will complain about the custom frequencies. If it doesn't work the radios are basically worthless for my use. Has anybody else had any luck hacking the Protalk radios for GMRS or Ham use? For those not familiar with these the radios they are restricted to a fixed set of frequencies the user can select from a list. You can't enter a custom frequency through the programming software or using the self programming feature of the radio.

Just for my info I went looking to see if there are in fact any digital voice capable digital voice satellites. I found one for D-Star. http://www.d-star.one

That's likely one of the real reasons why it isn't tried. Most of the digital modes have fairly wide signals compared to side band. A SSB signal is around 3KHz, correct, while some of the digital mode signals are like the following examples: 4K00F1E – NXDN 6.25KHz digital voice (IDAS, NEXEDGE) 4K00F1E – dPMR 6.25KHz digital voice (Typically not used in North America, used in the EU) 7K60FXE – 2-slot DMR (Motorola MOTOTRBO) TDMA voice 8K10F1E – P25 Phase 1 C4FM voice 8K30F1E – NXDN 12.5KHz digital voice (Wide DAS, NEXEDGE) 9K36F7W – Yaesu System Fusion C4FM (Voice Wide) 22K0D7E – TETRA DMO Voice Some of those linear translators don't have that much bandwidth to begin with. Using digital isn't going to be welcomed and very highly discouraged, not because it can't be done with the right equipment. As I said before any signal that's transmitted is always an analog type regardless of what information is being sent. The main difference is how the signal is shaped. Simple rectangular pulses are not sent because the bandwidth required is stupid wide. Various types of pulse shaping is used. One such shape is GMSK. There are others with different properties. https://www.oscium.com/sites/default/files/WhitePaper_Simple_Signal_Shaper_GFSK.pdf http://www.sss-mag.com/pdf/gmsk_tut.pdf https://www.researchgate.net/profile/Thierry-Turletti/publication/2575678_GMSK_in_a_nutshell/links/0deec517e72247f39d000000/GMSK-in-a-nutshell.pdf?origin=publication_detail I get the point about possible signal inversion occurring in a linear translator. However that would depend on the design. I would guess not all of then do so. That how the convention between using upper or lower side band on HF originated, selecting the high or low side mixing product of the VFO with the local oscillator depending on the band. Also likely the reason why simply connecting the output from a receiver's discriminator to a transmitter's modulator might not work has to do with the frequency accuracy. With 4FSK it's critical the frequency shifts are right. Being off too much the RX radio can't decode the data. That means the level being fed into the transmitter's modulator has to be very carefully controlled to achieve the expected frequency shifts. That's also assuming the frequency shift is a linear function of the modulation voltage, which it might not be.

I’m not sure it won’t work in particular with a linear translator. The input signal is typically down converted to a base band IF frequency then up converted to the output frequency. The signal is not demodulated during the process. Remember that digital voice is really transmitted using specially modulated analog RF such that it carry’s digital data. The pulse shape is such that it has a very narrow bandwidth. So long as the translator is linear and the bandwidth of the digital signal fits within its input and output band range it should be repeated just fine. The one area that is difficult as you pointed out is the Doppler shift. Most of advance digital modes use some form of multi level frequency shift keying. For it to work you need very good frequency accuracy. With good orbit parameters and model a computer controlled radio readjusting the frequency on the fly might work. It works well enough for SSB on the birds up there now since as we well know an error of 10’s to 100’s of Hz results in unintelligible signals so there is a chance.

I guess if you really want a challenge try running a digital voice mode through one of the satellites. I remotely remember reading about a Ham that claimed it was accomplished with DMR.

I did at one time. https://www.g0mrf.com/ao-40.htm I had a portable setup for AO-40, 70cm SSB uplink working with an 11 element M Squared Yagi, https://www.m2inc.com/FG4205011 and the down-link was on 2.4GHz with a UEK-3000 down converter to the 2 meter band working with a 24db dish antenna. http://websites.umich.edu/~umarc/files/misc/UEK-3000.pdf https://www.radiolabs.com/wireless/wifi-antennas/directional-wifi-antennas/parabolic-grid-wifi-dish-antenna-24db-2-4-ghz/ The radio I used at the time was a Yaesu FT-847 with an optional after market IRAD RX IF crystal filter for SSB. I made a couple of contacts through it. The down-link signal wasn't that strong. https://www.hamradio.co.uk/userfiles/file/FT-847.pdf https://w6aer.com/ft847-inrad-filter-modifications-upgrade/ Because of some screw up the satellite ended up in a very highly eccentric orbit. At the farthest point the distance was around 40K miles. The delay in the down-link in the head phones was about a 1/2 of a second, very noticeable and hard to adjust to hear one self with a delay. The advantage at that distance is the satellite hardly moved for about 10 to 15 minutes making manual static pointing of the antennas practical and almost no Doppler shift. I lived in a ground floor apartment at the time so I needed to to drag the whole antenna setup outside every time. That was done late at night to attract far less attention. The last thing I wanted were the other tenets calling the local PD thinking I was some kind of spy or terrorist. The van had enough strange looking antennas on it as it was and I got a few people driving circles around it at shopping centers staring at them while giving me weird looks. Oh well. 8-/ I made a few contacts on FM through a low earth orbit satellite, mode U/V, from a mobile using an Icom IC-706MKII I had with some simple vertical antennas on the roof. Those satellites tend to get very busy since they are far easier to work.

Have you asked for permission to use the Troy575 repeater? If not you have nothing to lose. I’ve had some luck running 15 watts and a high gain mobile antenna from Oxford to the north. I’ve also heard a few mobiles almost out to Novi to the west. I’m in Sterling Heights so that puts me about 4 to 5 miles from the repeater. Works pretty well at 1 watt on a portable. TROY 575 Repeater Group: [143] Members: 07/03/2022 1. ADMINISTRATOR: Dave R.: WRAB 719 / K8RDG / Mio / wrab719@gmail.com

OK. It wasn't clear to me which one you where talking about. Yeah, I wonder why it was canceled. 8-))

If you’re referring to WROY767 his license was granted on 12/31/2021 and good to 12/31/2031. He also seems to be located in the middle of an extensive linked digital Ham repeater network too being located in Venice Florida. https://ni4ce.org/nxdn-digital-communications/

People might find this an interesting reference to read. R-HDB-24-1996-PDF-E.pdf

At $3K not exactly cheap and you still need two antennas with feed line and space to mount the separated antennas. So apparently the repeater is really two separated independent FHSS radios that exchange the digital audio using a fast Ethernet link. Since you can’t use cavities to isolate the TX and RX you need the physical separation between the antennas to provide the necessary isolation. Calling it a repeater is sort of stretching the definition a bit. It looks more like two independent network connected radios.

It’s not a question of what I like. More like what fits the application given the limitations. For example with GMRS you only have 22 simplex channels and out of that 7 are limited to just 1/2 watt unless the FCC allows more power for digital, which is possible I guess. That leaves just 15 frequencies, not a big hop set otherwise. I’ve also been looking at some of the testing and research for a “possible” move to digital voice on the VHF marine band. I believe that’s on the docket for the WRC23 conference. Apparently TDMA voice modes like DMR and TETRA are not being recommended. They are leaning to systems using FDMA. One that I saw mentioned was dPMR. While some like DMR, don’t get me wrong I like it too and have been looking at getting a few more radios (NX-1300DU which I don’t have in my collection for example) and I do have a few XPR6550’s. I read some interesting comments about DMR not being a huge favorite of frequency coordinators particularly when 6.25KHz channels are in the area and they need to assign additional ones. The reasons mentioned were some I never considered before. And yes I’m aware of the long thread on digital modes back in 2021. I even made a few posts to that thread myself towards the end. Funny thing is nobody seemed to mention spread spectrum technology that I recall.