MMDVM and Legal ID intervals

MMDVM_HS Hat hardware
N6PL
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MMDVM and Legal ID intervals

Post by N6PL » Sat Nov 21, 2020 4:13 am

I've seen this topic come up from time to time and the answer seems to be that if CWID is set for (say) 10 minutes and there is DMR traffic being broadcast at the expiration of the 10-minute timer then the CW ID will not be broadcast. This is understandable of course since DMR and a CWID cannot be sent at the same time, but shouldn't the firmware simply note the expiration of the ID timer and ID the next time the transmitter unkeys?

The way it seems to work now, if the channel is busy and the transmitter happens to be keyed at each CW ID time then the system essentially will never ID (even if there is plenty of dead time to do so if an ID was pending.) Does this mean that all MMDVM-based repeaters in the US (where ID is required at regular intervals for voice and DMR) are operating without a legal ID capability? Am I missing something?

Thanks

KE7FNS
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Re: MMDVM and Legal ID intervals

Post by KE7FNS » Sat Nov 21, 2020 11:07 pm

N6PL wrote:
Sat Nov 21, 2020 4:13 am
I've seen this topic come up from time to time and the answer seems to be that if CWID is set for (say) 10 minutes and there is DMR traffic being broadcast at the expiration of the 10-minute timer then the CW ID will not be broadcast. This is understandable of course since DMR and a CWID cannot be sent at the same time, but shouldn't the firmware simply note the expiration of the ID timer and ID the next time the transmitter unkeys?
No. The firmware doesn't really have anything to do with the CW ID timer. There is no RTC (realtime clock) on the STM32 processor so it has no concept of time.
N6PL wrote:
Sat Nov 21, 2020 4:13 am
The way it seems to work now, if the channel is busy and the transmitter happens to be keyed at each CW ID time then the system essentially will never ID (even if there is plenty of dead time to do so if an ID was pending.) Does this mean that all MMDVM-based repeaters in the US (where ID is required at regular intervals for voice and DMR) are operating without a legal ID capability? Am I missing something?
CW ID timing isn't something that is handled in the MMDVM/MMDVM_HS firmware, the timing is handled in the MMDVMHost software.

You should file an issue at the github repo.
https://github.com/g4klx/MMDVMHost/issues

From what I can see the CW ID counter/timer never gets incremented while any of the modes are "busy" only when the system is idle. In a perfect world the counter/timer would be in its own thread/process so that it cannot be "paused" like the way it is currently implemented.

I think that changing the way it works to kick off a CW ID when the 10 minutes are up is going to end up with it losing someones transmission on a busy channel instead of it buffering that transmission while the CW ID is being handled and then returning to that buffered transmission. That is at least my guess as to why it was written the way it was.
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N6PL
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Re: MMDVM and Legal ID intervals

Post by N6PL » Sun Nov 22, 2020 12:19 am

Thanks for the comment and insight. Yes, I realize that the ID is implemented in the MMDVMHost software and 'firmware' was a typo on my part. I researched how ID is done in the MOTOTRBO/commercial world and the system does (or at least can be optioned to) enforce ID at specific intervals, even if a transmit permit has to be delayed in order to provide time for the ID. But less of an issue in a commercial environment due to the 30 minute ID period, which is often ignored anyway. From what I read CWID is frequently disabled in commercial DMR systems simply to avoid any headaches or user confusion.

So in the amateur realm it seems to be a 'don't ask - don't tell' kind of situation, in that many busy MMDVM-based repeaters are probably not IDing at 10-minute intervals (or 30 minute, or 60 minute if the system happens to be keyed at the wrong time.) Not in strict adherence to the regs to be sure but not a problem for me if it isn't for the FCC I guess. There are many gray regulatory areas with respect to amateur digital comms these days.

KE7FNS
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Re: MMDVM and Legal ID intervals

Post by KE7FNS » Sun Nov 22, 2020 4:01 am

N6PL wrote:
Sun Nov 22, 2020 12:19 am
Yes, I realize that the ID is implemented in the MMDVMHost software and 'firmware' was a typo on my part.
People mistakenly use the two terms as if they are the same thing and interchangeable.
N6PL wrote:
Sun Nov 22, 2020 12:19 am
I researched how ID is done in the MOTOTRBO/commercial world and the system does (or at least can be optioned to) enforce ID at specific intervals, even if a transmit permit has to be delayed in order to provide time for the ID. But less of an issue in a commercial environment due to the 30 minute ID period, which is often ignored anyway. From what I read CWID is frequently disabled in commercial systems simply to avoid any headaches or user confusion.

So in the amateur realm it seems to be a 'don't ask - don't tell' kind of situation, in that many busy MMDVM-based repeaters are probably not IDing at 10-minute intervals (or 30 minute, or 60 minute if the system happens to be keyed at the wrong time.) Not in strict adherence to the regs to be sure but not a problem for me if it isn't for the FCC I guess. There are many gray regulatory areas with respect to amateur digital comms these days.
A 10 minute interval would actually not be correct for Amateur use either. The US rules state IDing every 10 minutes during a conversation and at the end of that conversation. I have no idea what the UK or EU rules are.

For a repeater, it would only have to ID once if it had been keyed up in the last 10 minutes. After 10 minutes of silence has passed from its last ID it is no longer required to ID because it hasn't transmitted. That is why when you key up an idle repeater it kicks off an ID immediately, its that idle timer resetting.

Most people that are running a repeater don't just hook up a hotspot to a giant tower/antenna and amplifier, they run specialized repeater controllers that handle all of the IDing and timers on their own.
If someones previous actions are any indication of their future actions, then I predict the deletion and removal of access will happen at any moment. 7-11-2020.

"07/13/20 This Website Has Been Taken Down" ... again :lol:

N6PL
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Re: MMDVM and Legal ID intervals

Post by N6PL » Sun Nov 22, 2020 5:00 pm

KE7FNS wrote:
Sun Nov 22, 2020 4:01 am
Most people that are running a repeater don't just hook up a hotspot to a giant tower/antenna and amplifier, they run specialized repeater controllers that handle all of the IDing and timers on their own.
That is not a correct generalization as there are many DMR repeaters using an MMDVM-based board (such as the Repeater Builder STM-32) as the sole controller. If you want a legal ID you could cobble up something external that monitors PTT and activates the DMR board inhibit line while you ID based on whatever logic you like, but an MMDVM software-integrated solution would be vastly superior.

KE7FNS
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Re: MMDVM and Legal ID intervals

Post by KE7FNS » Sun Nov 22, 2020 7:06 pm

N6PL wrote:
Sun Nov 22, 2020 5:00 pm
That is not a correct generalization as there are many DMR repeaters using an MMDVM-based board (such as the Repeater Builder STM-32) as the sole controller.
I mean repeater owners/operators in general, not just DMR repeaters exclusively.
N6PL wrote:
Sun Nov 22, 2020 5:00 pm
If you want a legal ID you could cobble up something external that monitors PTT and activates the DMR board inhibit line while you ID based on whatever logic you like, but an MMDVM software-integrated solution would be vastly superior.
Or you can just buy an IDer.
If someones previous actions are any indication of their future actions, then I predict the deletion and removal of access will happen at any moment. 7-11-2020.

"07/13/20 This Website Has Been Taken Down" ... again :lol:

N6PL
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Re: MMDVM and Legal ID intervals

Post by N6PL » Mon Nov 23, 2020 1:40 am

KE7FNS wrote:
Sun Nov 22, 2020 7:06 pm
I mean repeater owners/operators in general, not just DMR repeaters exclusively.
In case I wasn't clear and as indicated in the subject line, the question is concerning MMDVM-based controllers specifically.

KE7FNS wrote:
Sun Nov 22, 2020 7:06 pm
Or you can just buy an IDer.
Nice if it were that easy but no, a simple off-the-shelf IDer wouldn't be adequate since you can't inject an external time-based CW ID into a DMR transmission without consideration of what is going on at the time, or at least not without severe disruption. Attempting to ID over a digital transmission would likely blank out any ongoing communications, so not really acceptable. What you would need to do is note the expiration of the ID timer and (if a transmission is currently underway) then when the transmitter drops disable TX permit while the ID is broadcast. That would have the possible effect of delaying TX permit to new callers for a few seconds, but would be much less disruptive than simply crashing an ongoing transmission. This could be done externally with some additional logic as described above (since some MMDVM boards have an external inhibit line that can be used to hold off transmission until an external ID is complete), but again it would be much better and easier implemented in MMDVM software.

KE7FNS
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Re: MMDVM and Legal ID intervals

Post by KE7FNS » Mon Nov 23, 2020 7:19 pm

N6PL wrote:
Mon Nov 23, 2020 1:40 am
In case I wasn't clear and as indicated in the subject line, the question is concerning MMDVM-based controllers specifically.
Forum discussions don't stay exactly on whatever subject the original post contains, they mutate and evolve over time as more and more posts are written.
N6PL wrote:
Mon Nov 23, 2020 1:40 am
Nice if it were that easy but no, a simple off-the-shelf IDer wouldn't be adequate since you can't inject an external time-based CW ID into a DMR transmission without consideration of what is going on at the time, or at least not without severe disruption. Attempting to ID over a digital transmission would likely blank out any ongoing communications, so not really acceptable.
That is not a requirement of IDing though. The ID transmission doesn't have to be the same mode, just the same frequency. Look into how the CW is actually transmitted using an ADF7021, it isn't a digital mode.
N6PL wrote:
Mon Nov 23, 2020 1:40 am
but again it would be much better and easier implemented in MMDVM software.
If you don't bring up the legality discussion in the proper place with the proper individuals, either a MMDVM-based repeater controller forum or the MMDVMHost github, then you shouldn't expect any changes to be made.
If someones previous actions are any indication of their future actions, then I predict the deletion and removal of access will happen at any moment. 7-11-2020.

"07/13/20 This Website Has Been Taken Down" ... again :lol:

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VK7HSE
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Re: MMDVM and Legal ID intervals

Post by VK7HSE » Wed Nov 25, 2020 12:31 am

Depending on the radio you are using, you can most likely implement what you are after from the radio. Pretty much all commercial radios provide a means to add an ID timer (Tait 80xx radio's have this)

I have my own system running here on a Tait TM8110 and I've setup a 10 minute CW ID and that's done from the radio and not using the ID options in pi-star.

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N6PL
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Re: MMDVM and Legal ID intervals

Post by N6PL » Wed Nov 25, 2020 10:49 pm

VK7HSE wrote:
Wed Nov 25, 2020 12:31 am
I have my own system running here on a Tait TM8110 and I've setup a 10 minute CW ID and that's done from the radio and not using the ID options in pi-star.
How does the radio handle the situation where the transmitter is keyed (meaning ongoing communications are active) in DMR mode when the 10-minute ID is due? If it simply steps on the digital transmission with the ID and interrupts communications then I wouldn't consider that acceptable. Or does it have some holdoff capability?

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