Lscott

That will be one of the issues with trying to get the FCC to approve the idea. There is an existing group of FM only users and how would allowing digital affect them? Many, I would guess, likely wouldn't have any need or interest in getting digital enabled radios. The current FM only radios fits their needs as is. The FCC would need to balance any proposed rule changes against the interest of those users. That will be the tricky part.

Do you have the service manual for the radios? Manufactures can and do change versions because of hardware design changes. That could apply to the display too. You simply might have a different, electrically, LCD display verses the other radio where they are not compatible. The service manual might show the differences.

Some of the above sounds like a rehash of topics discussed before. I'm surprised more haven't downloaded a file I posted on 7/25, 3 so far and I was one of them to test it, in this thread detailing my thoughts on the topic along with a lot of links to prior background material. In there I go over some points where a couple of modes might be a good choice even if they are not the current favorite and why. The idea is what could be proposed in a filling with the FCC they will seriously consider. Before that happens there has to be sound arguments why it can and should be done.

I wouldn't be concerned about FRS. It's a different service, and effectively unlicensed at that. If an FRS user wants to use digital voice, well let them pay for a license. It's another perk of getting licensed besides using higher power and access to repeater operation. The repeater idea has merit. I believe that dual mode equipment is available, which will automatically switch between analog and digital modes. The negative aspect is too many non-technical GMRS users have trouble figuring out what offsets and tones are judging by the frequent posts on the forum asking for help. Now throw in color codes, slots, talk-groups and user ID's, well even some experienced radio buffs have a bit of a problem with those.

So, given the current regulations, and assuming the FCC would change it's mind, what do you think has the best change of getting serious consideration? We have to be realistic here. The FCC isn't likely to make major changes that could have negative impacts on existing users. They made a mess of things previously by allowing the marketing of dual service radios, GMRS/FRS, and tried to clean it up with the 2017 changes. This is the conversion we need to have and have an open mind about it.

The spec's for the 2730A are hard to compare to the 2821D since the sensitivity units are different. You need to convert the 2730A to uV units. -10dbuV -> 0.32uV -5dbuV -> 0.56uV https://static.dxengineering.com/global/images/technicalarticles/ico-ic-2730a_sn.pdf file:///C:/Users/kcs/Downloads/IC-2730A-brochure-12-01-17.pdf

So far no. The programming software seems to set all of the “unused” channels frequencies to zeros if I switch between 8 to 2 channel models. It also sets those channel options to default values too. That’s VERY inconvenient. I had hoped it wouldn’t so I could do most of the channel setups through the software and just manually hex edit the code plug for the custom frequencies. I need to experiment and see if hex editing the code plug for just the frequencies and load it into the programming software if it leaves them alone for the extra memory channels so I can write it to the radio. If it does I’ll have to reverse engineer the code plug structure for a memory channel completely to figure out where the options are set, bandwidth, power, scan etc. and hex edit those for each one. If that works maybe I can write a utility to read in the code plug and make the changes, then save it. Right now the frequencies are stored as packed BCD in little endian format in 4 bytes. The tones are stored as a 16 bit unsigned integer in 2 bytes, also in little endian format. Why the difference? Beats me. I didn’t write the radio programming software. Some of Kenwood’s other radios the code plugs are encrypted using a simple XOR method. The key is stored in the code plug in a fixed location and might be different from one code plug to the next for the same exact model radio. I’ve seen the install key in the code plug along with radio serial numbers too for some models. I think this is done so Kenwood can trace where the code plug came from.

The issue was looking at the range limit due to problems when the radios can't sync the time slots from signal delays. If the time slots overlap then communications basically fails. That was the focus of the mentioned section in the ESTI standard. I was curious if anyone has experienced this, or at least can be reasonably sure that was the cause. The second issue was clock drift in the radios. Unless one is using extremely accurate clocks, like synchronized to an atomic standard, they will drift over time. BTW old cell sites used Rubidium atomic clocks but now use GPS disciplined clocks to maintain sync. https://www.thinksrs.com/products/prs10.html https://en.wikipedia.org/wiki/GPS_disciplined_oscillator The clock would be the internal master oscillator reference used for the frequency reference. After some period of time, likely just seconds, after the initial slot synchronization for a transmission the slot timing may overlap between slots 1 and 2. Remember the frequency drift is for both radios at each end. Again communications fail. That seems to place a piratical limit on the transmission time length too. If you look closely at the cheaper DMR radios, compared to the more expensive commercial versions, they have sort of crappy oscillator accuracy and drift spec's. For example the few Motorola XPR-6550's I have spec at +/- 0.5PPM, my Kenwood TK-D340's are +/- 1.0 PPM. The popular D878UV is +/-2.5PPM ! Ouch. Some base radios, and or repeaters, could be using OCXO, oven controlled crystal oscillators, to maintain frequency accuracy and very low drift rates. The best hand held radios only have TCXO, temperature compensated crystal oscillators, because the power drain for the oven heater is far to high for battery pack powered radios. http://www.realhamradio.com/GPS-oven-journey.htm https://www.electronics-notes.com/articles/electronic_components/quartz-crystal-xtal/tcxo-temperature-compensated-crystal-xtal-oscillator.php

I've read about there being range limitations when using TDMA digital modes, like DMR, due to clock drift in the base and mobile stations. The issue seems to be the slot timing verses distance and length of transmissions. See section 10.2.3.1.3 on page 112 in the following link to one of the ESTI DMR standards. https://www.etsi.org/deliver/etsi_ts/102300_102399/10236101/02.03.01_60/ts_10236101v020301p.pdf Anybody have any experience with this or did the detailed calculations for their installation? I've seen comments where some have gone to FDMA type modes to avoid this issue.

You can try enabling through the option menu window.

If "N" connectors are too big and you need something small that can be weather proofed, good luck with BNC's, and high frequency rated have a look at the RG8 mini UHF type. https://www.everythingrf.com/tech-resources/connectors https://www.amphenolrf.com/connectors/mini-uhf-connectors.html

If you check you'll see just about every radio that says it's "wide-band" really is spec'd for 16K0F3E, not the FCC authorized 20K0F3E for GMRS. The 16K0F3E was the old business wide-band specification. Just about every GMRS repeater on the air is build using old Part 90, business band, equipment with the 16K0 spec. Many of the currently sold GMRS radios are old repurposed business radio designs, or amateur gear, with tweaked firmware to make them compliant with the FCC rules. The 16K0F3E spec seems to be particularly true of the new Chinese manufactured GMRS specific radios. One would have a difficult time telling the two apart, 16K0 verses 20K0, on the air. I suspect the FCC could have changed the rules to make 16K0 the "official" FM standard for GMRS and likely nobody would notice.

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.