[aprssig] RS Digitravelr Power Mod

[Lance Cotton]

Chuck Gooden wrote:
> Purchased a Radio Shack Digitraveler GPS off ebay a few weeks ago and
> would like to get it working for APRS use in my van.
> 
> Could someone please provide the details on the Power mod for the Radio
> Shack Digitraveler GPS unit.  Looking at:
> 
> http://w5ac.tamu.edu/~kj5o/digi_traveler_mod.html
> <http://w5ac.tamu.edu/%7Ekj5o/digi_traveler_mod.html>
> 
>>From the picture, it appears the power regulator is simple soldered to
> the bridge rectifier output leads with a wire connected to the left most
> lead.  Is this correct or is there more to it?

What the picture illustrates is how to modify the digitraveler to accept 
  up to 35V DC on a spare wire in the RJ11 connector. (In the 
digitravelers I received, this was the RED wire in the included cables, 
YMMV)

When this mod is in place, power can be supplied in the same connector 
that serial data goes over. The reason the red wire was chosen (it's the 
Digitravelers RS232 RX wire) is that there must be some non-zero voltage 
on that wire to wake up the digitraveler. Make sure you don't also 
connect the red wire at the other end of the cable to a computer's 
RS232-TX wire AND 12V at the same time!

With this mod in place, I think there may be some interference if you 
also put AA batteries in the digitraveler. A diode placed somewhere 
ought to fix that, but I never took the time to think about it, since I 
never plan to use batteries in mine.

Soldering to the rectifier outputs was chosen just because it's an awful 
convenient spot to solder to.

-Lance KJ5O

-- 
J. Lance Cotton, KJ5O
joe at lightningflash.net
http://kj5o.lightningflash.net
Three Step Plan: 1. Take over the world. 2. Get a lot of cookies. 3. Eat 
the cookies.