[aprssig] Filter to obtain specific stations in a region

[Bill Vodall WA7NWP]

> No, there are no and/or operators in javAPRSFilter (or any other
> operators except for negation).  All the filters are additive.  That
> said, if you have a/57/-125/41/-104 in your filter, then you will get
> all of the a and W stations which are in that region (making the s//a/W
> filter not necessary) 

Additive as you said..  I get all the stations in the region and the a-W
stations from all the other regions.

> so I am not sure what you are trying to accomplish. 

It's an IS-2-RF widget so we can share the active Winlink (or other
resources) with RF users...

>  If you only want a and W stations in that region (no
> others), there is not an easy way to do this other than doing a negation
> on all other symbols.

I see where I could get essentially what I want by declaring 3 large "-a" filter
regions to exclude stations from the rest of the world.  A bit ugly but it
seemed to work.  My complements to the javFilter programmer for handling
magic like this.


> javAPRSFilter was designed to provide a limited feed to clients allowing
> them to exist on lower bandwidth connections and slower machines.  It
> was not designed to be a GUI filter which, I think, is what you are
> asking for.  That was left to the individual client authors.

Which is what I'll implement now.  Given the very limited feed of "aW" stations,
it'll be simple to drop the ones out of my range of interest.

Thanks,
Bill - WA7NWP