Ham PBX?

[KC2UGV]

So, while researching VoIP (Voice over IP), I came across an article that was talking about how many companies are replacing their two-way radios with Wifi SIP (SIP is a VoIP protocol) phones.

It dawned on me then. How could amateur radio ops build out a cellular network of sorts.

You have a repeater (Run-of the mill) that is really a Packet node. The node only accepts packets that are SIP packets over the amateur spectrum. Each user of the Repeater has their personal node configured as a SIP phone, with a designated extension.

You want to "call" a particular ham, you "dial" his extension using your DTMF pad. And, always, there is a conference that anyone can dial into (Extension 1000 or something).

Now, I know this might ruffle some feathers, but it would serve emcomm purposes well (Imagine having an ad-hoc cell network that is always there), repeaters can be linked over any IP tunnel with IAX (Inter-Asterix Exchange), and moving from repeater to repeater is easy as pie.

Any thoughts? Ideas? Critiques?

[W3WN]

Why?

[KC2UGV]

Why?

Why:
* Multiple clear channels carried on a single repeater pair for multiple conversations (Channel multiplexing)
* VM storage a la Packet Mailboxes
* Industry standard protocols for client and for system inter-ties

And, the most important of ALL reasons:
* Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art.

[W4RLR]

Why:
* Multiple clear channels carried on a single repeater pair for multiple conversations (Channel multiplexing)
* VM storage a la Packet Mailboxes
* Industry standard protocols for client and for system inter-ties

And, the most important of ALL reasons:
* Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art.

I like it.

[NQ6U]

It's an interesting idea. There are certainly plenty of underutilized repeaters out there that could be converted to this type use. The hardest part would be writing the repeater control software; do you know any hams with the proper skills who would be willing to donate that much time and effort to the project?

On edit: Ideally, the software would be written to run under Linux, for both cost and reliability concerns.

[KC9ECI]

I think it's a neat idea and might be fun to play with, but too complicated for emcomms. For that I want something simple, that just works and does so with the minimum of equipment and will work until the infrastructure is back up and running.

[n6hcm]

On edit: Ideally, the software would be written to run under Linux, for both cost and reliability concerns.

you could probably extend asterix to do this. it already has the concept of modules which can be dropped in to enable different types of adapter support.

[KC2UGV]

It's an interesting idea. There are certainly plenty of underutilized repeaters out there that could be converted to this type use. The hardest part would be writing the repeater control software; do you know any hams with the proper skills who would be willing to donate that much time and effort to the project?

On edit: Ideally, the software would be written to run under Linux, for both cost and reliability concerns.


you could probably extend asterix to do this. it already has the concept of modules which can be dropped in to enable different types of adapter support.

Yeah, the whole idea is SIP over AX25. Asterix already supports SIP trunking, out of the box. I like building neat things out of COTS parts.

The one thing I'm seeing is this may need to be on 440 and above, if multiplexing is the goal. I think a 2M channel can only support one concurrent voice channel at a time, due to legal reasons, and technology (Codec2 being the closest to 2.5KHz vocoding, and open source, and AMBE2020 would not be able to be fit into a COTS solution).

[NQ6U]

Good point, Corey. You have to be 220MHz or above to do spread-spectrum stuff in the US.

Actually, now that I think about it, the 220 band would be a good one to choose--it's hugely underutilized right now and it would be great to come up with something that encourages people to use it more before it goes the way of 11m or something.

[W3WN]

It's an interesting concept... and yes, 220 MHz and above would have to be used due to current legal limitations on multiplexing and spread spectrum and such.

And if the goal is to see if it can be done, go for it. No learning experience is ever wasted.

But if it can be done... what would you do with it once it's done?

I'm not trying to be negative, but I just don't see the practical application. I hope that just means I'm overlooking something.

[NQ6U]

I'm not trying to be negative, but I just don't see the practical application. I hope that just means I'm overlooking something.

You could be right, Ron, it might not be all that practical. But how much of what we do as hams truly is? Even the practicality of amateur radio emcomm is debatable. But the spirit of experimentation is what makes ham radio fun and, in my opinion, doing it just to see if it can be done is reason enough to try it.

[KA5PIU]

Hello.

Want something like that, and it is a 100% proven platform?
It is called trunking.
An old UHF trunking system will do everything you want, and more.
Since P25 is the way to go, and everyone is pushing 700/800MHz, UHF trunking equipment is heading out the door, cheap!
I have several Astro Sabre talkies in UHF that do MotoTrunking that I got for zip, just the right place at the right time.
And since the feds ARE upgrading to P25 the 420MHz systems will be converting.
The amount of hardware hacking needed to take MotoTrunking to 440MHz is zero, retune the duplexers and reprogram and you are all set, the keyboard out of band trick works just fine.
http://wiki.radioreference.com/index.php/San_Antonio_Military_SmartZone
I was very picky and went only for full keypad last generation radios, and wound up with a box of them.

[NQ6U]

The only problem with that Rudy is that everyone would have to go buy an old Motorola radio. Corey's idea could be executed using existing ham radios that most of us already have and cheap bog-standard PCs.

[N4VGB]

So, while researching VoIP (Voice over IP), I came across an article that was talking about how many companies are replacing their two-way radios with Wifi SIP (SIP is a VoIP protocol) phones.

It dawned on me then. How could amateur radio ops build out a cellular network of sorts.

You have a repeater (Run-of the mill) that is really a Packet node. The node only accepts packets that are SIP packets over the amateur spectrum. Each user of the Repeater has their personal node configured as a SIP phone, with a designated extension.

You want to "call" a particular ham, you "dial" his extension using your DTMF pad. And, always, there is a conference that anyone can dial into (Extension 1000 or something).

Now, I know this might ruffle some feathers, but it would serve emcomm purposes well (Imagine having an ad-hoc cell network that is always there), repeaters can be linked over any IP tunnel with IAX (Inter-Asterix Exchange), and moving from repeater to repeater is easy as pie.

Any thoughts? Ideas? Critiques?

Since this seems to be related to using the old packet repeaters for this purpose, it wouldn't work around here. The local digipeater is in the floor of a friend's basement and has been there for years. Nobody was using it any longer so the club took it down and dismantled it. Same for most of the club & private operated digipeaters in this region, gone and forgotten.

Linked repeaters we got out the yazoo. In fact we can link repeaters over a vast area of the South. Large scale emergencies over the region was the idea behind the linked repeaters. They served use very well during emergencies in standard mode FM voice operation. I really don't see how your approach would work any better for emcomms? It's best to have open communications during emergencies so all can stay on the same page.

There was an old setup named Selcall for VHF-UHF land mobile service. It was nothing more than DTMF activated squelch control but accomplished something of a private voice line setup for users who were sick of listening to radio traffic that didn't concern them all day. I haven't seen that old gear in use for many years now.

I think something like your vision can be implemented in the D-Star setup. That is big in neighboring AL but hasn't caught on well in TN. I think there is one D-Star repeater in Nashville and thats the only one I've heard about.

[N8YX]

I think something like your vision can be implemented in the D-Star setup. That is big in neighboring AL but hasn't caught on well in TN. I think there is one D-Star repeater in Nashville and thats the only one I've heard about.
This was my thought as well. I would love to have the facilities to put a full-scale D-Star system and a WIRES-enabled FT-8900 on the air as a gateway.

[NQ6U]

The trouble with D-Star is that it uses a proprietary digitalization scheme with a chip available only from a single source. Corey's idea could/would be an open standard that could be implemented by anyone.

[KC2UGV]

The trouble with D-Star is that it uses a proprietary digitalization scheme with a chip available only from a single source. Corey's idea could/would be an open standard that could be implemented by anyone.

That is the killer for using the DTSAR protocol for this: AMBE202 is a closed system, and can not be implemented in software (So, it won't work for Asterix).