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[aprssig] Solar Powered Digi

Robert Bruninga bruninga at usna.edu
Thu Dec 23 15:44:36 UTC 2004


Normally a power-saver circuit kicks back in in only 5 seconds.
So you would have to have an external 555 to get any 
decent time out of it...  bob


>>> Wes Johnston <wes at kd4rdb.com> 12/22/04 2:00:53 PM >>>
I was thinking about something like this the other day.... a solar digi
out in
the swamp between my home and work - No, I'm not shrek, I don't LIVE in
the
swamp ;-)

My idea was to put and HT in the digi because of it's power saver
fuction on
144.99-600.  Now, ordinarily the power saver would prevent the HT from
hearing
the first part of a packet.  The trick here is that since there isn't
much
traffic on 144.99, if the HT just caught the tail end of a packet, it
would be
enough to kick it out of power saver mode.  Then when the next packet
came
along, if the power saver hadn't kicked in again, the digi would hear
the whole
packet.

Another thing that will kick an HT out of power saver mode is to open
the
squelch.  The trick is to have watch the DCD LED on the TNC, and if a
carrier
triggered the DCD LED for say 100mS (easily done with a kpc3plus), then
trigger
a 555 timer (you thought I was going to say basic stamp, didn't you?)
that would
force the squelch open on the HT for say 120seconds.  This I think
could be done
by simply shunting across the "bottom" of the squelch pot on the HT. 
You'd have
two thin wires hanging out the case running to an optoisolator (ie
relay). 
Could probably get by with a FET, 100uF cap and a 1M'ish resistor too.

What makes this work is that as I approach the digi, it hears my
packets, but
not good enough to decode.  So chances are that the first packet it
hears, it
would not have decoded anyway - but that was enough to wake up the
"sleepy
digipeater".  After that it keeps listening for 2 minutes after I'm out
of
range again.

Wes
--



Quoting Robert Bruninga <bruninga at usna.edu>:

> A real power-saver on SOlar Powered Digis:
>
> If you need a digi in an area, but cannot afford the huge
> solar power system to keep it on the air most of the
> time, consider making it an ALT-INPUT digi on 144.99
> instead of a full service digi on 144.39.
>
> The TX load will be 2 to 5% of what it would be if the
> input was on 144.39 because it will only digipeat
> the locals that need it, and not the 98% of other
> digipeater traffic coming at it from all directions.
>
> Your digi will listen on 144.99 for locals and low power
> trackers (probably fewer than a dozen) but will still
> digipeat them over to 144.39 to join the network.
>
> Just a thought for some special applications...
> bob
>
>
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