[aprssig] Pocket Tracker???

Robert Bruninga bruninga at usna.edu
Sat Nov 19 16:41:54 CST 2005

>>This might interest you [for an APRS TX kit]
>Please tell him to keep it at 12 watts and don't
>cut it back to 5W!
>The duty cycle of an APRS transmitter even at
>30 second rate is less than 3%.  Thus the
>12 watt device (probably takes 25W DC
>input power) but at 3% dutycycle this is only
>an average device dissipation of 750 mW
>and can easily be dissipated by just the PCB.

>>> wa8lmf2 at aol.com 11/19/05 9:37 AM >>>
>This translates into a continuous drain of 83mA 
>from a 9V battery!  Obviously not practical.

Ah, but that was for a 30 second  rate which is
excessive in most cases.  Drop it back to a 2min
rate and the average power from the battery is
21 mA which could run for tens of hours.  But
I didnt realize we were talking about a 9V battery
originally, and such a battery wouldnt provide the
peak current of 3 amps in the first place.  I doubt
he'd even get the current for 5W even if he used 
a NiCd instead of alkaline, but then those are only
really 7.2v batteries and and now it would need
probably 2 amps even to get 5 W of RF.

So if we are talking about a system to run on
a 9V battery, then I will butt-out since one 
can't get that much power out of one of those


 Looks like a high-power PT would have to be in a substantially larger 
box in order to accomodate a much larger battery.    But then, at least, 
one could easily add the 60mA drain of a GPS-18 or similar.   

Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      14400    [Think bottom of the 2M band]
Home Page:          http://wa8lmf.com

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