[aprssig] Automatic omni DF query

[Wes Johnston, AI4PX]

On the tracker side, we need to think about making sure we limit "who" will
answer.  querying every tracker in the world and then them answering could
be akin to a DDOS attack, eh?

Maybe we need a range parm on the tracker to limit it's range to 100km by
default from the query station?  Of course it could/should be user
adjustable, but default low.

Wes

On Mon, Feb 9, 2009 at 2:44 PM, Scott Miller <scott at opentrac.org> wrote:

> My new T2-301 trackers are frequency-agile and can measure incoming
> signal strength, so it occurred to me that it'd be useful to define an
> APRS query that'd cause all capable stations to QSY their receive side
> to the specified frequency for a second, take a reading, and then come
> back and report what they heard in omni-DF format.
>
> Before anyone asks, these particular units won't work for 121.5 - I've
> only been able to get them to receive as low as 127 MHz.
>
> Based on some experimentation with a service monitor, it looks like the
> usable RSSI range is roughly -128 dBm to -68 dBm.  If I'm reading my
> conversion chart right, for a 50-ohm system that's a little more than
> the standard S0-S9 range.  Seems kind of low at the top end, but I'll
> have to do some field testing and see what I get.
>
> What I'm thinking of is something like this:
>
> ?DF146.520?<optional footprint>
>
> The response should be a DFSshgd omni-DF extension followed by the
> frequency.  I'd prefer the frequency to be a standard part of that
> response, so clients could be made smart enough to separate out multiple
> DF plots.
>
> Comments or suggestions?
>
> Scott
> N1VG
>
>
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>



-- 
Wes
---
Where there's silence, there is no Hope.
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