MMDVM and Legal ID intervals

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N6PL
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MMDVM and Legal ID intervals

Post by N6PL »

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?

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N6PL
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Re: MMDVM and Legal ID intervals

Post by N6PL »

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.
N6PL
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Re: MMDVM and Legal ID intervals

Post by N6PL »

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.
N6PL
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Re: MMDVM and Legal ID intervals

Post by N6PL »

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.
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VK7HSE
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Re: MMDVM and Legal ID intervals

Post by VK7HSE »

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 »

VK7HSE wrote: Wed Nov 25, 2020 12:31 amI 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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VK7HSE
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Re: MMDVM and Legal ID intervals

Post by VK7HSE »


How do you handle the situation where the transmitter is keyed (meaning ongoing communications are active) in DMR mode when the 10-minute ID is due?
It does so when the frequency becomes available. Now don't forget that you callsign is embedded into all 5 digital modes. Granted that isn't human readable like CW or a voice ident. But I'm pretty sure that would still be sufficient to pass for mandatory station ID. However naturally I'm not proficient in every countries stance on the matter.

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Last edited by VK7HSE on Wed Nov 25, 2020 11:03 pm, edited 1 time in total.
N6PL
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Re: MMDVM and Legal ID intervals

Post by N6PL »

VK7HSE wrote: Wed Nov 25, 2020 11:03 pmIt does so when the frequency becomes available.
Ah, good. That is the functionality that should be available natively in MMDVMHost so that MMDVM-controller (only) systems aren't dependent on the external radio to have that capability, but until that time it is up to the operator to come up with something suitable (assuming that they are aware of the issue.) In my case I added some external logic to accomplish the task.

Neither am I all that familiar with regulations in other countries, but since commercial digital formats such as DMR or P25 do not embed callsigns (rather only a system ID) in the transmission they do not carry legal amateur identification suitable in the US.
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