[OZAPRS] HF MOBILE beaconing, food for thought.

Richter, Mike W Michael.Richter at team.telstra.com
Thu Jul 8 22:41:55 EST 2004

I have looked at the IPS Hourly Area Predictions from IPS 
For an HF Gate in Alice Springs, at this time of year for 10Megs  (Eastern
Standard Time)
 - from 10.00-18.00 the skip zone will reach out about 900km from the HF
Gate, reducing to 500, then reaching 900 again.
 - from 20.00-08.00 the skip zone covers all of Australia
for 7 Megs  (Eastern Standard Time)
- from 10.00-18.00 the skip zone will reach out about 300km from the HF
- from 00.00-08.00 the skip zone covers all of Australia
For short distance communications throughout the night, you would have to
go down to 2MHz.
So a 40m HF Gate would help provide coverage for those travelling in
winter between 18.00 and midnight.


 -----Original Message-----
From: Robert Thirkettle [mailto:rob.thirkettle at canterbury.ac.nz]
Sent: Thursday, 8 July 2004 07:16 am
To: Tony Hunt; ozaprs at marconi.ics.mq.edu.au
Subject: RE: [OZAPRS] HF MOBILE beaconing, food for thought.
Hi All           At last I see skip distance being talked about for APRS.
It is no different than SSB if you want to talk to a VK6 from VK2 you
would depend the where we are in the sunspot cycle, you would probably use
20M as this would give the best signal. APRS is no different except you
actually need a better signal to noise ratio for AX25 data than voice.
What this means is if we want reliable system we need a wide spread of HF
gateways so any packets have a fair chance of reaching at least 1 gateway
some where or we need gateways that are use more than 1 frequency and the
user just changes frequency to suite conditions. 


I personally favour a mix of the 2 options I have been a strong supporter
of 40M as this band is very good for the medium distance skip 200-500km.
This band is better suited for the shorter distances between gateways here
in ZL. 30M is good for the 800-1200 km these skip distances are for
daylight hours as during darkness hours this all changes dramatically. I
usually see the VK 30M gateways here at dawn and dusk. We also need to
take into account the declining sunspot cycle as we continue to the bottom
over the next few years we will see the skip distances on 30 and 40 meters


Regards Rob Thirkettle ZL3RX          


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