[aprssig] APRS low-power-local ALT input channel
bruninga at usna.edu
Mon Sep 27 13:11:41 CDT 2004
>>> wes at johnston.net 9/27/04 11:38:41 AM >>>
>I did some stats with 4 home stations (10 min each) and
>4 trackers (1 minute each) and came up with... 264
>seconds out of 3600 seconds per hour, 7.3% utilization
> on 144.99 if everyone in my local area ran 144.39+600.
>This number is a little higher than Bob's. But it's in the ballpark.
I'll buy that, but it is a bit high, because it assumes
those 4 trackers are in the area for the full hour. Either a commute
is shorter than that, or he traveled out of area..
>>Finally, let's look at your digipeater design .... Every time
>>the WIDEn-n side transmits, your local receiver is
>>desensed and cannot copy anything on the "local" side.
>Right again.... We either need vertical separation of the
>144.99 and .39 antennas, or to run cavities.
>This means we have to double my 7.3% number above
AH, but now you are starting to mix apples and oranges.
(deaf trackers versus all other stations). We need to keep
clear what issue we are talking about here. I have only
been addressing the alt-freq idea independently of what
kind of station uses it..
>Now if we can forward packets to the digi from the alt
>input site in such a way that it does not desense the alt
>input's receiver, we have a winner.
Yes, but this is only an advantage for deaf trackers... not
for regular stations...
>If we end up with multiple alt input digipeaters in a metro
>area, we need to take care that they can all hear each
>other. This is getting convoluted though.... I fear that
>by trying to cover all the bases and possibilites I am
>muddying the water.
Yes, keeping it simple is the only way to achieve progress
one digi at a time... Jumping thorugh all kinds of complexity
and hardware to change an 86% success rate up by
just 7% is just not worth it when the 86% rate is already
far better than trying to operate a low p ower device on
>The maker of the pocket track has said that it will use
>144.39 and (144.99 or 144.34). It appears he selected
>144.34 at the request of a couple of his first customers
>[for balloons] and because it was close in prox to 144.39.
>He has offered to sell a pocket tracker on any freq you
>ask for... so this is really a non-issue.
Yep, that is all we are trying to accomplish here, is to help find
a way to make plenty of more room available on APRS
for these and other local users of APRS.....
>And finally, if CSMA works so well, why did they
>switch to DAMA in europe?
Good thought wes! Yes, the missplaced belief that CSMA
works well on simplex AX.25 with shared high-site digis
and low-site users is one of the things that has always held
back packet from its potential for HAM radio... since day
one in the 1980-'s
good thoughts Wes...
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