[OZAPRS] HF Configuration.

[Richard Hoskin]

Gday Dick,

HF is a different beast to VHF. The capacity to carry data on HF is 1/4
that
of VHF. VHF is for short distance near to real time tracking, HF is for
long
distance in the ball park tracking.

If you are driving along in the never never how often do you need your
position to be updated? It really doesn't matter to the observer that you
are another 1.2Km down the track or are doing a right hand turn. If you're
within 10 or 20 Km of your last posit that's good enough for most
observers
who are hundreds or thousands of kilometres or more away from you. If you
are using APRS as a safety measure in the bush, it won't take searchers
too
long to find your vehicle if you are 10 or 20 km from your last posit.
Besides you wouldn't rely on APRS as your sol means of communications,
you'd
be on voice too.

When your mobile how do you know when HF propagation is good or bad at the
Receiving Gate 1500Km away? And how do you know when it's changing? If you
are 1500Km from the Receiving Gate in one direction and another mobile is
1700Km from the same Receiving Gate in the other direction chances are you
will not here him and he will not hear you. However the Receiving Gate
with
its superior installation will hear both stations and if one station has
an
aggressive beacon rate the other station will miss out on getting any
posits
through. That's not playing cricket.

A high beacon rate has the potential to interfere with stations in EU or
the
US as Ross VK3MY has pointed out in previous emails. You may never hear a
DX
station mobile but a Receiving Gate with a good installation in another
county has a good chance of hearing your beacon. They wouldn't be to happy
if you where creating interference to their local HF APRS system due to
excessive beacon rates. 

Ok that's my 5 cents worth.

Cheers
Richard
VK3JFK


> -----Original Message-----
> From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
> Behalf Of VK7DIK
> Sent: Thursday, 12 April 2007 5:52 PM
> To: ozaprs at aprs.net.au
> Subject: [OZAPRS] HF Configuration.
> 
> 
> 
> Hi All,
> 
> 
>        I have been watching the HF parameter discussion with interest. I
> would like to
> add my thoughts to the mix. As I understand it all HF base stations
> basically are receive only feeding the NET/VHF. I hope this is correct
as
> this is what I interpreted from the information I got from various WEB
> sites explaining HF APRS use. No arguments from me here. So onto mobile
HF
> stations. To my way of thinking at any given time there really are not
too
> many mobile stations driving around with HF on board. Band conditions
are
> not the best so I believe a reasonable smart beacon rate is justified so
> that the maximum possibility exists for the HF mobile station being
heard
> and relayed onto the NET/VHF. Lets face it, as with VHF APRS its nice to
> see all the base stations on the map but I for one am much more
interested
> in seeing mobile station. I belive a regular smart beacon rate is
> justified and should be used at all times. When the band conditions
> improve we may need to make changes but for now, more is better.
> 
> 
> Cheers, Dick.
> VK7DIK
> 
> Please Note.
> My e-mail address at home is vk7dik at dodo.com.au and work is
> dick.vanbeek at zinifex.com
> If your address book do not have these then please change it.
> 
>
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