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

Scott Miller scott at opentrac.org
Wed Jan 25 12:08:53 EST 2017

My multi-port gadget is making progress, too.  Right now my focus is on 
the repeater controller version as a follow-on to the ADS-SR2, but the 
same hardware will work equally well as a dual-port digipeater.  The 
next hardware revision will have a third input-only port for a dedicated 
control channel.

I also just got a BASIC interpreter running on it that will replace the 
Tracker2/Tracker3 series' funky bytecode interpreted scripting system.

It's not as powerful as a Raspberry Pi but it boots in half a second and 
draws less power.


On 1/25/2017 8:40 AM, John Langner WB2OSZ wrote:
>> 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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