[aprssig] Mobile/Tracker TX power

Robert Bruninga bruninga at usna.edu
Mon Oct 30 20:04:54 CST 2006

> The D7 is working acceptably at 0.5w, with a long whip, 
> and batteries last longer.

For what it is worth, the TX power on most APRS mobiles is
usually insignificant compared to receive power.  The RX and TNC
are on all the time drawing about 70 mA (I think) and so that is
70 mA-Minutes.  Whereas the TX transmits for only 1/2 second
every 60 seconds and draws maybe 1.2 amps at high power (?).
But this is only 10 mA-minutes.  So the TX power is only about
14% of the total battery drain. 

So, yes, it saves battery power to run on low power, but only
less than 15% of life, yet running on low power sacrifices over
7 dB of link margin.  In many cases, getting in, is worth more
than saving just 15% of battery life..

If you run a 2 minute rate, then the TX power is down to only
about 7% of total battery life power, and is usually
insignificant to mission success compared to being heard..

Anyway, just a thought.
Bob, Wb4APR

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