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22831RE: [aprsisce] Dual iGate: Terrestrial and ISS

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  • Robert Bruninga
    May 8, 2013
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      > 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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