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[aprssig] HF options

Jim Lux jimlux at earthlink.net
Thu Dec 20 06:23:19 UTC 2007



-----Original Message-----
>From: Scott Miller <scott at opentrac.org>
>Sent: Dec 19, 2007 12:02 PM
>To: Jim Lux <jimlux at earthlink.net>, TAPR APRS Mailing List <aprssig at lists.tapr.org>
>Subject: Re: [aprssig] HF options
>
>6 meters had crossed my mind, but I've never used it at all.  I've heard 
>the California Highway Patrol uses it, too.  That'd definitely be 
>preferable to messing with HF.  Power is a major concern, since the 
>transmitting sites will not have commercial power.

But how much power?  

Data rate, frequency of transmission, etc. will determine all that.  If you only need to blurp 60 bits every hour, a 100W (DC draw) transmitter sending at 10 bps will only take 60 seconds out of the 3600, so the average power draw would be less than a couple watts.

This is sort of like the problem we face sending data back from deep space at JPL, except you have a lot more options (i.e. you're not mass limited, so a high peak/average ratio isn't as big deal).  

The transmit power is probably quantized (i.e. you're limited by the power dissipation of the active device) in some chunk size, so you probably want to run at the upper limit of a given power category.


Jim, W6RMK





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