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[aprssig] Lotsa ears, big mouth concept.

Frank or Barbara Rossi n3flr at bellatlantic.net
Tue Oct 13 03:51:35 UTC 2009


I was going to put a DIGI at 2,600 Ft on Chestnut Ridge in Eastern 
Westmoreland County.
South Western Pa goes from Mt Davis 3,200 Ft to the 600 Ft range at the 
Ohio River,
Pittsburgh Pa at river level is about 700 Ft 35 miles away.
I found that the receiver was never quiet, many doubling stations that 
could not hear each other, but I could hear them.
My conclusion was that the site was to high, hearing stations to far away.
I was hearing DIGIs in Eastern Ohio when they were not getting doubled.
Essentially the coverage far exceeded what the Aloha Circle should have 
been for full channel usage.
Even at 2,600 Ft there was still shadows.
So I abandon the Idea of the DIGI at 2,600 Ft in favor of more DIGIs at 
lower altitude.
In Westmoreland County a DIGI at 1,400 Ft can hear 2 or 3 other DIGIs, 
that is good for a network.
Less shadows, your hop count does get used up at less distance, but that 
is OK.
2 to 3 hops is enough for local/regional coverage and to reach an I-Gate 
in WPA.
N3FLR - Frank


On 10/12/2009 1:33 PM, Keith VE7GDH wrote:
> Wes AI4PX wrote...
>
>> Just to throw something playful / constructive out there.  I had an
>> idea a few weeks ago about how to have a digipeater "network"
>> that has many receivers and one transmitter.  This is just a concept
>> so bear with me.
>>
>> 1)have one high centrally located digi.  Output on 144.39 (or your
>> local aprs frequency). This site has a 70cm transceiver for getting
>> data from the yet to be described receiver sites.
>> 2)have several low receiver sites around town. They listen on 144.39
>> and send all data (KISS frames?) over the 70cm link to the main site.
>
> It almost sounds like you are trying to replace the principal of having
> fill-in digis that respond to WIDE1-1 at low elevations and high digis
> that respond as well to WIDEn-N. If you were successful in getting
> everything from all digis on the described network from a large enough
> area to the "big mouth" digi, you could end up with a situation where
> the "big mouth" digi was transmitting almost continuously even if it
> couldn't hear everything that the low digis were hearing. When APRS was
> new and there were very few users (before I became involved) it was
> probably a good idea to have high digis. Now that the number of APRS
> users has increased, and especially in areas where there is very high
> density of APRS users, having high digis is counter-productive. Up to
> a point, your described network could be useful. Once APRS use increased
> to the point where it is spewing out packets well outside the individual
> users ALOHA circle, it could end up being not useful.
>
> Just my thoughts. Perhaps someone else can see some benefit from this.
>
> 73 es cul - Keith VE7GDH
> -- 
> "I may be lost, but I know exactly where I am!"
>



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