[aprssig] Pocket Tracker???
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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