[aprssig] Correct PSAT & igating

la3qma at aprs.la la3qma at aprs.la
Tue Jun 9 02:13:30 CDT 2015


Quoting "Kenneth Finnegan via aprssig" <aprssig at tapr.org>:

> On Mon, Jun 8, 2015 at 10:42 AM, Max Harper <kg4pid at yahoo.com> wrote:
>> Kenneth, maybe you are missing the point. I do this for fun and to prove to
>> myself that I can do it. I don't do it to prove anything to anyone else.'
>
> If we aren't talking about getting proof online that you have bounced
> a packet off a satellite, then you're correct; I have completely
> missed the point. What are we talking about?

The point using satelites is to go trough them. So even if i can talk  
voice on a simplex frequency with a local ham locally thats not the  
same as doing it via a satelite. The same thing relates to i.e aprs.


>> And to add an sgate mode to aprx is hardly crippling it when it   
>> solves problems.
>
> I don't understand what problem it solves. What's wrong with your
> packet destined for being relayed through a satellite accidentally
> getting I-gated directly by someone else nearby? This guarantees that
> your packet also makes it online, instead of making it dependent on
> you successfully reaching the satellite and back down to Earth.

Using APRS on a satelite frequency the whole point is to go via the  
satellite and not trough a terrestrial system. But we still need the  
IGATE to receive all data from the satellites even telemetry etc. But  
from the users only packet via a satellite.

> I interpret what is being suggested here as deliberately removing
> first-hop I-gating from the 145.825MHz network, which just removes the
> rock solid I-gate coverage near each ground station.
>
> What about when an APRS satellite beacons its telemetry? When your
> sgate hears this packet direct, will it drop it since it doesn't have
> a consumed APRSAT* hop? How does it know what is a satellite and what
> is another ground station near-by? (Hint: Whitelists are not a correct
> answer for the entire network.)

No it should gate all traffic from the known satellites and ground  
stations relayed trough them.

> Now, if we're only talking about your one specific ground station and
> not the 145.825MHz network at large, then I am much more indifferent.
> You don't need my permission to develop your own personal patches for
> aprx.

"all" the 145.825 network should use a patch like this.

But if you don't see the need maybe we can move the discussion on how  
to solve this using other methods.

Modifying APRSC to change the dupe-check and to add filtering on APRX  
could probably be a branch. But my C experience is not good enough but  
i might be able to do a rough change and let people tidy up the code.

Or a perl script using a TNC and injecting data to APRS-IS based on  
some simple satellite rules.

Kai Gunter
LA3QMA



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