intermod

We agree on that. Since emission designators need to be added anyway, the FCC just needs to add one or two new sentences in the rules to allow for that. This current restriction you noted is: "§ 95.1765 GMRS frequency accuracy. (b) The carrier frequency of each GMRS transmitter transmitting an emission with an occupied bandwidth of 12.5 kHz or less must remain within 2.5 ppm of the channel center frequencies listed in § 95.1763 under normal operating conditions." Small problem. G

8 GMRS repeater channels X 4 slots/channel = 32. Each DMR repeater can support two slots or conversations, right? It is four slots because *two* DMR repeaters can be placed within one GMRS channel, if you operate one higher and one lower in frequency. Thus, 32. But maybe you were just showing where I said four.

And this is true. Each slot can carry an independent and simultaneous conversation. If I have 2 DMR signals or carriers, 2 slots each, that is four slots. You understand that each DMR repeater can support two simultaneous calls or conversations, correct? That is why I used the term "conversation" as using slot or channel may get confusing. G

Yet I never said I could squeeze in four . Strangely, I think we are in agreement here, however. Just one example. There channels in the VHF and UHF commercial bands remain 25 kHz wide like GMRS (see 152.72 MHz, 454.350 MHz, etc.). These are under FCC Part 22, not Part 90. Within the 454.350 channel we placed one DMR signal 6.25 kHz below and one 6.25 kHz above the center at 454.350. So that provides for four simultaneous conversation paths (four slots). I am currently experimenting with placing a third DMR signal centered on 454.350 MHz, but geographically separated from the other two to limit adjacent channel interference. So far this is working great as long as the separation is adequate.

You may be mixing up channels and slots (or talkpaths). You are correct - two DMR carriers/signals can fit within a single analog carrier. That is what the chart shows. But each DMR carrier/signal provides two simultaneous talk paths, correct? So you end up with four talk paths in the same amount of spectrum as one FM signal that can only support one talk path. A DMR repeater requires F7D and F7E. DMR handheld and vehicular radios require F1D and F1E. Only the F1D is permitted (so you can operate DMR on GMRS for non-voice - like texting). They key here is the "E" for Telephony (voice) versus 'D" for Data transmission. The "7" indicates "more than one channel" of information is being carried (the repeater has two timeslots). The handheld and vehicular radios use "1" because they only can talk on one slot at a time.

I like cat videos.

But the government works for us...how could this be? Agree on the business approach - its very flexible. But there is a community/social aspect to GMRS that is hard to replicate on business. What I have advocated is for CERT and other public safety groups consider business spectrum, or even public safety spectrum (many do qualify for it - its already happening). These groups are more "insular" in a (positive) way - they have a very defined group of users, where many don't have a desire or need to meet others outside of that group or specific city/county. This would offload some of the co-channel issues. With regard to business spectrum, it had been difficult to find a clear channel pair in the metro areas. One previous poster noted that there should be quite a bit of VHF and UHF spectrum available as many businesses have moved to other bands and cellular, POC, etc. I have not dug around for a few years so this might be possible. Edit: Also - another possible drawback of using business or public safety spectrum is that the repeater site owners could start charging us much more for site rent unless I could convince them "its non-profit, just like GMRS or HAM". But then again, maybe I just place a label on the business channel repeater that says "GMRS" and hope they don't check.

Sorry that you have been triggered. I have more quotes if you need them. How much money do you have?

My wording could have been better. My main point was that, when the FCC permits repeaters in a shared service, repeater users cannot always protect simplex users from interference (IX). So when you are planning a repeater, digital or otherwise, while I try and work around a local simplex group that call a certain channel home, eliminating interference is not always possible. Thus, simplex users cannot expect interference-free operation (except intentional IX).

4K0 dPMR is definitely much easier to fit in. Even having several high elevation repeaters, I would not have any issue with 4K0 stations 12.5 kHz away from my inputs. Even high power mobiles. I likely get more interference from the narrowband analog radios there now, especially when they are within a few miles of the repeater. The commercial frequency coordination standards originally allowed new 4K0 stations to be installed 12.5 kHz away from 20K0 (or like you mention 16K0) without getting any approval from the wideband users - even at the same repeater site. So this is well established. But that was also with tighter frequency stability standards. Maybe this is the first step to obtain acceptance of digital modes.

I think I might know about that P25 system. The FCC is short-staffed as has little interest in pursuing things like this unless many complaints come in. However, is there a victim here? We have had the same response here from some new users. Now I provide a URL link to a recording of what DMR sounds like on an analog radios so that they don't keep trying to access the repeater when its being used for DMR, or complain that there is noise. Or show them what a busy light is. The encryption issue is a bit more serious. It is just one checkbox in modern Part 90 gear and your encrypted. No sure encryption on shared channels is really the right thing to do. Using Part 95 equipment certification would likely solve most of that on GMRS.

Correct - experimental. The purpose was to "establish whether digital operation could co-exist with analog on shared spectrum". So far we have shown that it can. We simply replaced an existing analog repeater with a dual mode model (analog/digital) at the same power level. So our analog users still use it normally. ABout 10% of the regular users operate DMR/analog radios.

I have seen that too. I experienced this on low-end equipment. G

That is a problem...makes me wonder if this was really dPMR? G

OK - everyone - please stope this discussion. I will advise Rich to disable further comments. Sorry to offend you.

This is a interesting paper. Particularly for our current conversation: "...First let us look at the currently authorized emissions for GMRS. Looking in 47 CFR Subpart E 95.1771 we find some surprising, authorized voice emission modes, A3E, H3E, J3E and R3E. All of these are several types of voice amplitude modulation, Single/Double Sideband with suppressed or reduced carrier etc. None of these official modes are compatible with the FM mode! Why isn’t the FCC worried about interoperability between FM and these modes?..." Was this ever submitted to anyone at the FCC (officially or otherwise?)

I see your point on nuisance interference to simplex users. So if I wanted to listen in carrier then I would be annoyed if there was a strong DMR "chainsaw" going. As I am in a dense suburban and urban environment, the contractor/bubblepack call tones/business traffic is so constant that I never go without CTCSS, even in simplex mode. We can no longer listen in carrier squelch mode. Back in the day we could work long-distance simplex or repeaters. This was caused by the FCC, and Chinese radio manufacturers who have discovered the GMRS market and flooded it with radios. So maybe the FCC should only permit digital in areas where everyone is already running CTCSS/DCS....maybe this is why we have had few complaints from others (we have been running a DMR repeater on GMRS since 2016). But from a really practical perspective, once the FCC permitted repeaters in GMRS, simplex users were no longer granted protection from repeater interference in any case. They effectively became secondary, so they must accept interference or move to another channel (or use CTCSS for nuisance interference like DMR or analog). Once the industry started addressing digital, they may even come up with a better squelch system for radios. I have always wished I could program a given channel position on my analog radios to decode more than one CTCSS/DCS code at a time (or, decode/unmute when *ANY* CTCSS/DCS code is present). Thus, when it heard a DMR, NXDN, P25, noise, etc. it would not unmute. This should be really simple with current DSP technology. But it would also mute simplex traffic with no CTCSS....so maybe there is an even better way: mute all digital traffic.

...but fades fast... Thankfully the kiddies with their bubblepack radios and annoying call buttons fade fast (or break)....

Being from California, I will admit we are victims of a few social-engineering projects that have gone, well, very badly. and we love sharing our great ideas with otehr states. But this will be different! Are you suggesting that we cannot trust our own government? But from another perspective - a digital transition is inevitable. Regardless of whether it worsens or improves things. This is because of commerce and greed (the American way). If GMRS licensees do not take this head-on now, the radio industry will do it for us (or "to" us...). We will not like the outcome. Evidence: the FCC's 2017 ruling that allowed unlicensed users on the 462 GMRS channels with two watts. That was likely the industry's influence. But as I outlined in other posts, if I replace my existing analog repeater with a DMR repeater, how would that create a problem for others? Now, if the area is already congested with repeaters, and I try and jam in a new repeater too close to others - DMR or analog - we may have a problem. But that is independent of the mode of the repeater, and its no different that the problem we have today.

Agree that having a set of new frequencies for any digital technologies would avoid some conflicts. VHF and UHF is getting really quiet. I wonder if you just found win-win between GMRS licensees and the business frequency coordinators (BFC). If the BFCs can make ~$35 per licensee (as opposed to $200-$300 for one license over a large area), they may make more money supporting GMRS. But it seems that building coalition of interested GMRS licensees to lobby for digital would be more attainable. We have been using a DMR repeater on GMRS since 2016 (at 2200' elevation). Its runs dual mode (analog an digital). We have had no formal complaints, and I am aware of a few other GMRS systems also running DMR. So presenting the FCC with several successful DMR trials seems like an easier approach. Not sure I understand how the flood of bubblepack radios impact digital. Do you mean there are too many existing analog radios to change them all out? I am not suggesting analog be eliminated - we would allow digital to-co-exist with analog. 99% of those bubblepack radios come pre-programmed with tone squelch activated so they never even hear the digital signals or anything else for that matter. And digital signals are not bothered much by analog or other digital signals.

If I replaced my analog repeater with a digital one, how would that cause more interference that my analog repeater if my analog did not interfere today?

If my analog repeater did not interfere with another today, replacing it it with a DMR repeater (same antenna, same power level) would not change the interference potential. If I added a new repeater near an existing repeater, then interference may result if they are too close. But it would not matter if the new repeater was analog or digital. Interference has more to do with signal strength of the two signals (the desired versus the undesired signal) than the technology. However, I will say that digital can be more annoying to listen to if you are receiving it on an analog radio. Analog signals are just more susceptible to interference than digital. But this is what CTCSS is for. This is why we can place two digital repeaters closer together than two analog repeaters on the same channel.

Correct that the radios must sync themselves when operating in direct mode; DCDM is one method to provide for two simplex conversations on one channel. They could still use the +/- 5 kHz channel center, and they would hear the repeater. But compliant DMR radios don't use both timeslots simplex/direct mode; they use an arbitrary slot established by the first radio that transmits. They still only transit 50% of the time (the transmitter keys on an off every 30? or 60? milliseconds - forget the number).

Ah! Another benefit of DMR: less users, which means less congestion. What model DMR radio do you use?

Was her name Karen?