[aprssig] 2 Port Digitpeater was: APRS UHF freq? (9600 baud)

Kenneth Finnegan kennethfinnegan2007 at gmail.com
Wed Jan 25 15:59:23 CST 2017

Agreed; we really shouldn't be setting up null-cable KISS crossbands for
APRS these days. Between Direwolf for its own modem and Aprx for other KISS
TNCs both having multi-port digi support, and single board computers /
MicroITX industrial PCs being so cheap, you can set up very intelligent
cross-band digi for not much more than the rest of the system expenses..

Kenneth Finnegan

On Wed, Jan 25, 2017 at 8:40 AM, John Langner WB2OSZ <wb2osz at comcast.net>

> > Has anybody actually succeeded in putting two KISS TNC's "back to
> > back" to form an independently operating (no computer between them)
> > two-way "bridge" to pass traffic bi-directionally?
> > Lots of suggesting that this could work, but has it been done?
> In theory it should work but it's not a proper solution to the problem.
> Here is why.
> When a packet is first transmitted, the via path contains information on
> how
> it might be forwarded by digipeaters.
> Each time a digipeater retransmits a packet, it modifies the via path to
> decrease the number of possible remaining digipeater hops.  This limits the
> number of times it can be retransmitted.
> If you were to simply retransmit what you hear on one frequency onto some
> other frequency, that would be OK if only one person was doing it.
> However,
> if you had two stations like this, that could hear each other, the same
> packet could go bouncing back and forth forever.
> To do it properly you would want to put an application between the two TNCs
> to perform digipeating by the normal rules.  There are countless digipeater
> implementations out there but I'm not sure how many of them can handle
> multiple radio channels at the same time.
> The "direwolf" software TNC can handle up to 6 radios at the same time and
> has the ability to digipeat between different channels in any combination.
> Run it on a Raspberry Pi and you have something smaller and cheaper than a
> stack of old TNCs, with better receive decoding, and vastly more
> versatility.
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