[aprssig] 6 meter APRS (KA nodes?)

[Bob Donnell]

Bob:

I'm not aware of any direct network building compatibility between the
KA-NODE protocol and the NET/ROM &  TheNET protocol.  Also to my knowledge,
there's no version of Kantronics firmware that runs in a TNC-2 and no
version of TheNET that runs in a Kantronics TNC.

That said, it's really quite easy to make two TNC's share one radio.
Basically the TNC's should implement True DCD (Kantronics does this with
software, TNC-2's can have it added in to the hardware), for the usual
benefits of faster carrier detection.  Tie the TNC receive audio inputs, the
TNC transmit audio outputs, and the receiver audio, via say a 1K resistor,
to raise the impedance to avoid swamping the TX audio, all together.  Set
the TNC transmit audio outputs such that they are of the same level, and
high enough so that when a transmission is being made the other TNC(s) can
carrier-detect the TNC that's keyed up.  Use a voltage-divider potentiometer
at this common-point connection to set the transmit audio level to the
transmitter microphone or data jack input for proper deviation.  Done, and
simple.  At one point I had either 4 or 5 TNC's sharing one radio this way,
allowing me, in 1990, to operate conventional AX.25, TCP/IP encapsulated
over AX.25, and instances of two bulletin board programs - different ones,
allowing me to test new software using the same radio as the existing BBS
service for the LAN I was on.  I think at one point I had TheNET in the mix,
too.  It all worked fine.  Sure, occasionally two TNC's would key up at the
same time - but would have done so with 2 or more radios anyway.  It's also
a great diagnostic tool - by turning the radio off, you can do close packet
inspection of your wired LAN - it'll look just like a quiet radio channel,
with the radio squelched.  The biggest challenge then is that some
implementations of TrueDCD don't handle the situation of a modem emitting no
data transitions very well - they think the channel is always busy.

73, Bob, KD7NM

-----Original Message-----
From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
Of Bob Bruninga 
Sent: Thursday, August 27, 2009 5:59 AM
To: bruninga at usna.edu; TAPR APRS Mailing List
Subject: Re: [aprssig] 6 meter APRS (KA nodes?)

On Second THought (about 6m)...

Maybe we should make these digis be KA PACKET NODE capable too?

Rationale:

1) we will never have wall-to-wall mobiles on 6m network.

2) So what else to use the channel for?

3) 6m is a great fixed-location long range channel ideal for EOC's and other
fixed emergency sites for fixed-to-fixed comms where general purpose comms
to all mobiles is not needed.  Since 2m and 70cm is so valuable for
emergency operations, using 6m from the EOC for fixed comms, minimizes
co-site QRM.

4) Duty cycle of a few mobiles should be able to share with some KA node
activity..

Although it would be nice to have KA nodes at each digi, I think that you
can use one digi to link between two KA nodes, so really, only every other
digi needs to be a KA node, and the ones inbetween can be a simple digi...

What else is KA node compatible?  Do the THENET ROMS work?  AH but then they
do not have WIDEn-N (now 6MTRn-N) simultaneous capability so would not be
suitable..

Just thinking out loud.

Oh, and lots of base station rigs now have 6 meter capability, so this
network does not need to be an orphan...

Bob, WB4APR


---- Original message ----
>Date: Tue, 25 Aug 2009 14:37:45 -0400
>From: aprssig-bounces at tapr.org (on behalf of "Robert Bruninga" 
><bruninga at usna.edu>)
>Subject: [aprssig] 6 meter APRS (a new wild-west RF domain)
>To: "'TAPR APRS Mailing List'" <aprssig at tapr.org>
>
>With the beginnings of a 6m APRS network in the Wash DC area, I threw 
>together a web page to  lead discussion of how we want to best use this 
>new effort:
>
>http://aprs.org/6m-aprs.html
>
>In highly congested areas, we do not cross beacon the stuff to 2 
>meters, but let the Igates provide the connectivity to these users.  In 
>other locations, they can be cross connected where loading permits.
>
>But all of these 6m mobiles are always reachable by Tone 100 Voice 
>Alert via a crossband UHF calling channel.
>
>And wont it really be fun during METEOR showers!
>
>Bob, WB4APR
>
>
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