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[aprssig] HF Gate Configurations

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Wed Jan 20 22:47:11 UTC 2010


Michael A. Kelly wrote:
> Could Bob, or some of you other suggest UI-View digi parameter
> settings for the HF digi port in Kiss Mode?  I have the vhf port digi
> set to Wide2-2 (near rural area in NC) and want to know how best to
> set the hf port.
>   

I was just playing with receiving HF APRS and found the following links 
discussing it (Google: HF APRS).

http://www.nwaprs.info/hfaprs.htm

http://www.winaprs.com/DOSAPRS/HF.TXT

And near the bottom of http://wa8lmf.net/DigiPaths/

(Signing here: Lynn (D) - KJ4ERJ - Just passing on the links!)

When you get REALLY out in the boondocks, an alternative is the _*HF*_ 
APRS system. Virtually all HF APRS in North America is on 30 meters 
using 300 baud / 200 Hz shift HF packet format on 10.149.200 / 
10.149.400 (actual mark and space freqs). This band is normally open for 
long-range (500-to-2000 miles) transmission around the clock (and isn't 
plagued by the massive shortwave broadcast interference that makes 40 
meters unusable after dark).   *CLICK HERE 
<http://wa8lmf.net/aprs/HF_APRS_Notes.htm>* for details on HF APRS 
operation.

The 30-meter APRS frequency is mostly populated by unattended Igates 
that gate transmissions heard to the Internet, and Gateways that 
retransmit HF activity to 2 meters where it can then find it's way to a 
normal 2 meter Igate. Normally on HF, you _*don't digipeat*_ on 
frequency -- HF propagation is too erratic and unpredictable. The 
typical path is either:

   1. No path at all - You hope to be heard directly by an HF igate
      station (which is almost certain to happen).
   2. *GATE, WIDE2-2* which tells the receiving HF station to retransmit
      you onto VHF. This will not prevent you from also being inserted
      into the Internet System directly from HF by a 30M igate. [The
      majority of HF gateways are using Kantronics KAM dual-port TNCs
      which have built-in ability to cross-gate the separate HF and VHF
      ports. ] This can either amuse or annoy VHF users in systems
      thousands of miles apart that suddenly start getting position
      reports from "DX mobiles" on their local 144.390 network. 

_/*NEVER  NEVER  NEVER*/_ gate VHF activity the other way to HF!!! HF 
operates at a mere 300 baud. Even a single moderately active 1200 baud 
feed from a two meter channel would monopolize the 30M frequency 
non-stop over half the country! 

Note that all this HF activity is done using SSB, not FM, which means 
your receiver has to be tuned v-e-e-r-r-r-y precisely (typically within 
10 Hz) and stay there indefinitely. Often you are shooting in the dark 
with no received signals to tune in to verify the frequency. Modern 
transceivers with 10-Hz resolution digital displays and (often optional) 
high-stability master oscillators can easily do this, but don't expect 
the vintage Kenwood TS-820 or Yaesu FT-101 VFO rig to be even remotely 
usable for this application. 

Note that the TinyTrak Ver 3.1 can do the 300 baud format required for 
HF, but earlier versions can't. The commercially-built TigerTronics 
TigerTrak can also do 300 baud HF but it lacks the TinyTrack's 
speed-sensitive smart beaconing. If you run a laptop mobile, an 
alternative is a software TNC that uses the sound card through a 
standard sound card interface (the same kind you would use for RTTY, 
PSK31, etc) . Both the AGW Packet Engine (freeware) and MixW ($60 
registerware) can act as HF 300 baud TNCs entirely in software.





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