[OZAPRS] HF MOBILE beaconing, food for thought.

Robert Thirkettle rob.thirkettle at canterbury.ac.nz
Thu Jul 8 07:16:12 EST 2004

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          

Dept  Physics & Astronomy

University of Canterbury     

Private Bag 4800,         

Christchurch 8020,

New Zealand

Tel: +64 3 364 2510

Fax: +64 3 364 2469

mailto:rob.thirkettle at canterbury.ac.nz



-----Original Message-----
From: Tony Hunt [mailto:wavetel at iname.com] 
Sent: Thursday, July 08, 2004 1:21 AM
To: bbeamish at bigpond.net.au; ozaprs at marconi.ics.mq.edu.au
Subject: Re: [OZAPRS] HF MOBILE beaconing, food for thought.


Hmm.. I see Richard is sugesting 10-15 minutes and Des is looking for 1.5
to 2 mins .. I said I was running 7 mins in the mobile.. Good to see I am
in the middle ground.. 


I would have to argue against the 1.5-2 mins Des.. Most days of late in
this last week Ive been seeing 4BBS 4CLM 4DMI when its up with
regularity.. You may not have seen me driving around but Ive copied all
yous guys up there both in the mobile and at home..


I started off this yesterday with the observation in regards to 2HL and
his aprox  30 second beacons..


Its hit and miss at times on HF I agree but 2HL was at 10am getting about
50-70 percent of his beacons onto our VHF net here and into the Igate and
likewise at 5pm when I got home he was getting 100 percent of them in.. It
was actually creating a noticable difference in traffic levels on 2m ..
Hence my comments..


As stated previously the Hop seems to be about 1000 km and as much as
2000km frequently.. That means I see VK3 most of the time VK2 nearly all
the time and VK4 as soon as the suns up.. Yep southern  VK8 would be a
good spot for a Gate..


I think we have started to develop the idea that its very hard to get a
posit through (as I know I was) but in reality we have had a severe lack
of Gates that was not realised until recently..

We need to be careful of a mentality where we think we will be able to get
the mobile tracking on HF to be as frequent or acurate as VHF Metro nets..
This will never be the case.. Lets face it if I am in the middle of the
desert a few Kms either way means nothing to most of us.. If we make camp
at night or for a few days then the last known posit is a fair guess at
being right..  


Its interesting to see that we have not seen a posit from Andrew on Findu
for over 9 Days up there in VK6 as well.. So now I am worried as to his
last known posit being relavant.. I did copy him earlier this week in the
mobile and he had started heading south towards Perth so hes probably near
Broome I guess but that posit never got onto the net.. I would sugest we
are better off on 20m now frankly for this path.. The occasional ZL on 30m
seems to bob up here giving the impression that the path streches out at
times but I guess in VK2/4/3 you would see ZLs more often.. As Ive said
Ive had up to 10 stations on the map in the car with regularity and they
are all east of here..


What we really need to look at with the HF gates is making sure whereever
possible to put them in quiet locations.. Ive had the good fortune this
last week or 2 to park the car in the hills on a job in the middle of a
padock well away from the noises of suburbs etc and the difference in the
map is amazing.. The signals that do decode and the distances are quite
impressive.. We know what its like with voice coms on HF to get a good
quiet locality but how much more so with packet on HF..


Thers my bit.. 

Tony VK5AH

----- Original Message ----- 

From: Brian Beamish <mailto:bbeamish at bigpond.net.au>  

To: OZAPRS <mailto:ozaprs at marconi.ics.mq.edu.au>  

Sent: Wednesday, July 07, 2004 9:27 AM

Subject: [OZAPRS] HF MOBILE beaconing, food for thought.


Hi Folks


I am not trying or even intending to stir up a hornets nest so please no
flack just constructive criticism if any.


Des VK4DMI-4 and myself think along similar lines on this.


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