[aprssig] simple digipeater
Stephen H. Smith
WA8LMF2 at aol.com
Tue Aug 17 02:49:58 EDT 2004
Christopher A. Kantarjiev wrote on 8/16/2004, 8:31 PM:
> I've been looking at the PocketTracker and considering how that could
> be the
> right model - a receiver and transmitter that are focused on APRS,
> rather than
> using an HT. A Picpac or something similar is about the right hardware
> for what
> I have in mind.
1) The PocketTracker has no receiver! It only transmits.
2) 2W telemetry link transceivers are commercially available and would
be perfect for this application. These devices, typically housed in a
small diecast box, normally don't have any mic amp or RX audio power
amp/speaker. You would connect the RX and TX audio and PTT line of a
TNC to this device.
For the ultimate low power consumption, use a Kantronics KPC3+ ( this is
the only TNC with the capability to do WIDEn-N digipeating out of the
To do it cheaply, use a TNC2 clone such as an MFJ-1270 or Paccom, and
replace it's standard firmware EPROM with one containing the freeware
UI-Digi firmware. This code essentially gives a TNC2 a "brain
transplant" and converts it into a dedicated intelligent APRS digipeater
with sophisticated dupe suppression and WIDEn-N callsign substitution
capability. Before programming the eprom, the souce code is customized
to include your call sign, beacon intervals, paths and messages, etc.
The result is that your personalized settings are literally "frozen in
stone" (silicon actually) when you program the eprom so they can't be
lost from a power failure, accidental reset, etc. Something to consider
if the digi is going to be in a remote, inaccessble location.
The downside of the TNC2/UI-Digi appoach is that a TNC2 consumes a lot
more power (300mA at 12VDC) than a KPC3+ (less than 9mA). A
consideration if you want to power this thing on batteries and solar
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
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