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[aprssig] Voice Repeater ==> APRS Interface

Robert Bruninga bruninga at usna.edu
Fri May 9 01:26:24 UTC 2008

> Have you considered that you are asking a 
> repeater owner or club to spend significant 
> monies to implement this?

AH, thanks for the feedback...  No. I see it as virtually no
cost.  As free as a software download in many cases..

> You are asking a lot of repeater and node (IRLP, 
> Echolink, other) to do a lot of work to make this 
> practical.

I don't see it that way.  I don't see these kinds of things as
much of an investment over what some hams do every day with
their time.  It could be 100% a software download with no
hardware at all for an Echolink or IRLP node.  One could just
download a new version. done.  The Echolink node would work
exactly like it does now.  The only difference is that if it
"hears a DTMF callsign" it just generates a TCPIP packet to the
APRS-IS just like any Igate does...  Zero investment on the
owners part, other than the download of a new version.

> You are asking at least 6 major controller 
> manufactures to code in features, which no 
> repeater owners (the ones who buy the 
> product) have asked for. 

They don't have to do it.  I look at is as more of an
opportunity for them... to offer their clients something new...
If they wanted it..  And in fact, it does not have to go at the
repeater site at all.  Anyone can put up a DTMF receive site,
all it has to do is hear the DTMF tones.

> If they had asked for these features, the controller 
> manufactures would listen to their customers. So far 
> the silence is deafening.

Look at the success of Echolink and IRLP and APRS and Winlink,
and PSK-31 or just about anything in ham radio for that matter,
nobody ever "asked" for it.  They were created by motivated
individuals and it just  happened.  Manufacturers that wait for
people to ask for something before being creative, are usually
headed for a dead end...

> As a repeater owner, it would be a distraction 
> to have users sending a string of digits, and 
> hearing a voice "read" APRS info out.

Some repeaters could use the activity.  Or having the repeater
announce "Welcome WB4APR" is no different on air time than the
typical user keying up his rig and saying "WB4APR mobile".  No
difference.  Except that in the APRStt DTMF version, the
transmission is machine and network readable and distributable
to the larger community of ham radio.  Not just falling on deaf

For those quiet repeaters that want to keep it that way, they
can disable the voice response, and the repeater controller
would not even key up the transmitter, yet still send the report
over to APRS anyway.

> In the APRStt Responds, you show an HT and 
> laptop at some repeater site.  

That was the concept for the last many years until I now realize
it is far more efficient to simply get the existing controller
or echolink or IRLP that is already doing the DTMF listening, to
simply add this extremely simple conversion gateway function to
their code rather than as you say, to add a whole new layer of
hardware and software to repeaters...

> At most repeater sites, adding any emitter 
> requires a full frequency study, may incur 
> extra lease costs, etc. 

At many repeater sites, it is trivial to link to a nearby APRS
digi line-of-site with only milliwatts on 144.39.  Integrating
such a low power APRS transmitter is pretty easy with a little
ingenuity.  It can also use a directional antenna too, probably
even getting down to milliwatts is sufficient except for some
cases of low end 145 MHz repeaters.

> Keeping a computer running at sites with high 
> RF levels is difficult. This is why no repeater 
> controllers use a general purpose PC with software. 
> They all use hardened, purpose-specific micro 
> processors. 

Yes, and I think it would not take more than about a few dozen
lines of code to do a rudimentary conversion from DTMF callsign
to APRS packet and is trivial for someone to add to such
dedicated micros if the implementer is motivated to do so.

> To get a reliable two-way access to the 144.39 
> network, at most sites, will require far 
> more radio than an HT, or even a typical two 
> meter radio. An outside antenna, feedline, etc., 
> would be required. No site manager wants a 
> rubber duckie or mag mount on the cabinet. 
> You are also expecting, on VHF repeaters, 
> to add another VHF radio to the mix. This could 
> get expensive to do. 

I think that a High-site-to-APRS-digi-site link is easier in
many cases than you suggest.  If it doesn't work at a given site
easily, then simply do not do it there, or do it down at
someone's house in the valley.

> Adding even a 5w 144.39 emitter in the rack 
> of repeater gear could degrade the repeater 
> performance. Especially the 145.xxx repeaters...

Agreed.  A low end 145 MHz repeater is not a good candidate for
anything to do with APRS unless you can operate in the milliwatt
range on 144.39... But I can think of many simple workarounds.
After all, that is the fun of the hobby...
>> So now I am approaching the repeater controllers, 
>> and the Echolink and IRLP and any other manufacturer 
>> of any device in HAM radio that already has systems 
>> that LISTEN to ham radio with a DTMF decoder.   All 
>> they have to do is take the DTMF callsign of any 
>> voice user and send it out their serial port to an
>> attached TNC, or send it directly to the APRS-IS.

> So now you want me (the repeater owner) to have 
> internet access or something to connect the repeater 
> to the APRS-IS, at the site? OR, you want me to 
> provide a TNC and Radio? (plus feedline, antenna, 
> and permission of the  site manager). Or you want 
> repeater controller manufactures to add enough 
> smarts and a network interface, to get this data 
> to the APRS-IS? This is hardly a simple thing.

AH, yes.  Any of the above..  Sounds like fun to me and kinda
what the hobby is all about especially in light of the
step=function improvement in ham radio situational awareness
that this simple capability can bring to all of its local

I don't expect most repeaters to do this.  But if just one in 10
did it, then look at the power gained to the community.
> "Even the old codger that shows up with his 
> venerable 25 year old IC-2AT can participate!"

> IC-2ATs and many "Codger" radios only offer 
> 12 digits, and * and # are already chosen.

OOPS, you got me there.  OK, the keypad has to be able to at
least send the A and D keys...  And I think that the only
practical use is to also have a DTMF memory so that you can send
your call with a single button push making it extremely easy to

By involving the manufacturers and VOIP authors, I am asking for
us to come up with a single universal DTMF definition of a
callsign, that can be transmitted on the input of any of these
devices that will not cause any problems to existing systems.
Once we come up with that, then we can go from there.  From what
I heard, starting with a # key is one safe option?  But I do
need the input of all DTMF applications to see if we can find
something that wont cause strange things to existing


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