[aprssig] [aprsisce] Dual iGate: Terrestrial and ISS

Robert Bruninga bruninga at usna.edu
Wed May 8 08:19:27 CDT 2013


> We've got a 30M gateway in the area,
> seems silly to have 2 within 20 miles of each other.

Not at all.  That is called spatial diversity and is a vast benefit for any
HF net.  Even if they were a few hundred meters a part, they would still
show diversity.  When one is in a fade, the other would not be.  Diversity
whether in the spatial, or time domain or any other domain is a great way to
improve link reliability.

> I want at some point to run HF VHF cross band,
> I have a fair amount of traffic going down the English Channel...
> Obviously there needs to be a fair amount of filtering on VHF to HF and IS
> to HF

Red flags going up here (though I have not followed the thread closely).
But here are the "rules" for HF/VHF gating established back in 1994 or 5 or
so.

1) Gating every packet from HF to local VHF is fine... but ONLY if we assume
everyone on HF is using a path no longer than GATE,WIDE1-1.  The idea being
that the packet is heard in the SAME local area as the HF=>VHF gate.  Thus
locals who know the GATer can work out if the load is a problem

2) Gating VHF to HF is strictly not desired under any circumstances *other*
than messages.  Messages are CALL-A to CALL-B and should go
anywhere/everywhere there is a path available.

3) There should be no DIGIPEATING on HF except for emergency messages or
live one-on-one testing for short periods.  The APRS HF network is the
worlds largest spatial diversity receiver.  Some gate, somewhere will hear a
packet if it is to be heard.  No sense doubling the QRM all the time by
digipeating.

Hope that helps.
Bob, WB4APR


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