[CRAPRS] APRS guidelines on ARES website

[Jerry Pasker]

Nice guidelines!  The APRS world continues to evolve.... slowly.  :-)

I agree that some coordination might be helpful.  

I don't know if I agree that it's possible to have too many digs in an area as long as the digis are properly coordinated.  I think the most important part of this is that all use the same delay settings/algorithm.  That's the key to keeping the channel clear.  The idea behind a coordinated delay is that say KD0EWX is driving down 151 near Anamosa, and transmits at 1 watt. It gets heard by both KB0QCL and K0HAM-10.  Both KB0QCL and K0HAM-10 get the packet, and both of them digipeat transmit the packet out at the *exact* same time.  Because they use half duplex radios,  neither K0HAM-10 nor KB0QCL is aware that they were both transmitting at the exact same time!   Meanwhile, at KD0PCP, the FM capture effect chooses K0HAM-10's booming signal over KB0QCL's nearly non existent signal, and I-Gates it.  No channel bandwidth is wasted.

One could argue that all of the digis doubling just end up wiping each other out,  and no one can make out the signal, but in reality, somewhere, some igate (or other digi) captures one over the other and hears the signal, and either passes it along, or gates it.

That's how it's supposed to work.  The digis are suppose to use the same settings/delays etc and the idea is that in a digi-rich environment, they all transmit at exactly the same time, and it's up to the FM capture effect to pick the strongest signal.  No channel bandwidth is wasted.  Years ago when I was getting in to APRS I read about this in the Los Angeles area, and that's how they solved their channel congestion.

If I'm wrong, and I very well could be using an outdated viewpoint on this, please explain.  Or if I'm just plain wrong, please enlighten me so I can get up to speed on a better way of doing it.

I'll be moving my digi soon from one of the highest elevation homes in Monticello to one along the river, (6 feet above the flood plain)  loosing about 140 feet above mean sea level of altitude. Not even sure if it'll be able to make it to K0HAM-10 after the move, so I may be rethinking the usefulness or existence of my APRS station entirely.

Thanks,

-Jerry


On Nov 1, 2013, at 9:00 AM, Scott Haney wrote:

> Posting from the CRAPRS mailing list:
> All,
> 
> I put up some APRS guidelines on the ARES website at http://linn.iowaares.org/?page_id=65 . I think they're pretty solid, but I'm always open to suggestions as to how to improve this.
> 
> I'm also wondering if we need a somewhat more coordinated approach on digis. I know that a) we have new people interested in APRS who want to put up digis (which we probably don't need), and b) we have at least one digi in the area that likely isn't identifying per Part 97 because it's not inserting its callsign into digipeated packets and beacons only every 30 minutes.
> 
> How do we get the word out?
> 
> Scott
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