[aprssig] Re: Feeding multiple stations into one for digipeating?

Stan - N0YXV n0yxv at gihams.org
Sun Jun 11 20:46:35 CDT 2006

Some where I thought I'd read something about doing what you want with
Pseudo TTY ports in Linux. Although this explanation is long it's really
only an overview. You'd create a Pseudo port such as /dev/ttyp3 and then
point that Pseudo port to the other "Receive Only" station. Then on the
primary large area "Transmit-Receive" station you would simply hook up
multiple serial ports. Say your main station was running Digi_Ned you'd have
the standard port /dev/ttyS0 with a TNC directly attached to the main
computer. Then you'd setup a Pseudo Terminal such as /dev/ttyp0 and point
that at another computer in another location that has a TNC attached. The
remote computer sends packets back by attaching your KISS TNC via ax.25 to
another Pseudo terminal on the remote computer. On the remote computer your
kissattach would look something like /usr/sbin/kissattach /dev/ttyp0 ....
When your done on the main computer Digi_Ned would be looking at what it
thinks are two TNC's. One located at /dev/ttyS0 and the other located at
/dev/ttyp0. The thing I can't remember is how to get your Pseudo terminal
attached to an IP address. Played with the idea a long time ago and don't
recall all the correct ways to do it.

As for the question _should_ you do it or not I'll leave that up to the
master minds. So far it looks like most people aren't following your
original question.

The question wasn't how to use RF to bring small coverage Digi's into a Wide
area Digi. The question...as I read it...was how to take small receive only
stations and bring those via IP into a central station. That way if two
packets are transmitted at the same time you can recover both. An example
would be if two stations send a packet at the same time but are far enough
away from each other so that neither transmitter can hear the other but the
central digi can hear both. Normally only one packet (or none) would make it
to the digi.

If you had two separate receivers feeding back into one central station you
might be able to recover both packets. That's assuming that one receiver is
relatively close to the first station transmitting and the other receiver is
relatively close to the second station transmitting. Both receivers would
hear the station that are close to them and capture a complete correct
packet for retransmission via IP to the central Digi where both received
packets could then be Digi'd out correctly over time. With correct dup
checking (which Digi_Ned does) it should work in theory anyway.

> -----Original Message-----
> From: aprssig-bounces at lists.tapr.org
> [mailto:aprssig-bounces at lists.tapr.org]On Behalf Of Patrick Green
> Sent: Sunday, June 11, 2006 6:46 PM
> To: TAPR APRS Mailing List
> Subject: [aprssig] Re: Feeding multiple stations into one for
> digipeating?
> I wanted to state that what I'm trying to do is capture small
> trackers better.  This is no different than what a multi-receive
> site repeater does.  It has a "voter" that takes the best quieting
> signal and transmits it.  I want to do the same here, If I have 4
> copies of the same packet each from 4 different participating
> receivers and the packet is eligible for retransmission, only 1
> copy gets sent out over RF.  The central digi will still be CSMA
> to the other traffic on channel.  I want to use the internet as the
> medium to bring the traffic to the central digi.
> 73 de Pat --- KA9SCF.
> On 6/11/06, Patrick Green <pagreen at gmail.com> wrote:
> > Hi All,
> >
> >   I'm wondering if anyone has ever used multiple receiver sites
> > for an APRS station.  I got an idea to run a couple stations in
> > the area into a single station that has a higher profile setup
> > in the area.  The idea is to have a couple lower profile
> > stations nearby relay its receive to the bigger station to be
> > dupe checked and transmitted out of the packets meet the normal
> > repeating criteria while the site itself still receive as it does today.
> >
> >   I have a station at a good location running Linux to support
> > multiple instances of APRS applications.  In this case I have
> > Xastir running for an end user station as well as using it for
> > I-gate functionality and I have Digi_ned running for its superior
> > digipeating capabilities.  The problem is the high profile stations
> > capture the receiver and to help in this area, I wanted to use
> > additional receivers to be to capture local stations better and
> > with a higher percentage than I am today.
> >
> >   I've run the Digi_ned portion to digipeat everything to a UHF
> > 9600 channel in the past and this worked well.  The packets were
> > dupe checked and I was able to hear every station that the site
> > heard in that configuration.
> >
> >   I want to go a step further and have some receive locations
> > that are nearby connect via the internet and relay all the
> > packets to the main station for digipeating if the packets
> > qualify for digipeating and that were missed by the main
> > station.
> >
> > 1.  Would APRSD work to do this?
> > 2.  How do I bridge BPQethernet?  If this would work, I could
> > use Digi_ned.
> >
> > Any information and ideas would be appreciated.
> >
> > 73 de Pat --- KA9SCF.
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