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[aprssig] APRS low-power-local ALT input channel

Wes Johnston wes at johnston.net
Sat Sep 25 14:08:54 UTC 2004


The way I see it, _if_ there is no other packet system on 144.99 (ie 
PBBS, DXcluster or other), then the only other people you could 
interfere with would be other APRS users doing the same thing you are 
doing.  APRS users clobber each other's packets all the time.... and the 
ones that upset me the most are the packets coming in with paths of 
(humorously) WIDE7-7, RELAY and (seriously) people running wide4-4 
streaming in from over 300 miles away.  On the receive side, when mobile 
I limit my kenwood radio to 100 miles or less so I don't overflow my 
GPS's 500 waypoint memory in a day.  On the transmit side, my mobile 
radio competes on even odds with those same stations I choose to 
ignore.  Now ask me if I would choose to compete (ie TX at the same time 
someone else does) with A)Literally 562 stations showing on my home 
station's map, or B)4 other users in my local area.  I would choose B.  
Both mean that I _might_ double with someone - those are the odds when 
you use the aprs network.

As long as the 144.99 receive antenna is low, you limit it's range and 
therefore you limit the number of users who can reach it.  I use a voice 
repeater all the time and take my chances on the occasional "double"... 
what's the difference between that and the occasional double on packet 
with the other 4 stations in my immediate area? 

Wes

M J wrote:

> But isn't this already happening on your primary frequency now (ie: 
> all of those Mic-E dataframes that I see on your findu system)?  They 
> seem to be getting through ok, aren't they?  What is to lose 
> in exploring a different channel that had infrastructure that was 
> actually designed to address the specific environment of low-power 
> transmit-only participants?
>  
> Asking from ignorance.
>  
> MJ (a non-ham list observer)
>
>
> */AE5PL Lists <HamLists at ametx.com>/* wrote:
>
>     I stand by my statement: it is bad
>     operating practice to transmit without listening first to prevent
>     intentional interference on a shared channel. It is bad data network
>     design to use a shared channel with no attempt to have a collision
>     avoidance method.
>
> Do you Yahoo!?
> Express yourself with Y! Messenger! Free. Download now 
> <http://us.rd.yahoo.com/mail_us/taglines/msgr/evt=26089/*http://messenger.yahoo.com>. 
>
>
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