[OZAPRS] HF Mobile beacon times

[Ron Perry]

On Wed, 2004-07-07 at 08:38, Richard Hoskin wrote:
> 
> Hi Tony,
> 
> The general concessus is to set HF posit transmissions to 10 minutes. I
> believe that it should be 15 minutes especially if the number of HF
mobiles
> increases. You just need to do the sums.
> 
> An average length APRS Posit packet takes 3 to 4 seconds to transmit on
HF.
> Assuming a channel efficiency of 30% for ax25 this results in a maximum
of 7
> stations being able to transmit per minute. At a transmission rate of
one
> posit per 10 minutes the maximum number of stations that can be in a
single
> APRS Gate's coverage area is 70 stations. This will be less as the Net
> stations transmit frequently and messages  and/or tuning may be under
way on
> the channel. HF Propagation is also an important factor in limiting
station
> numbers.
> 

I've tried to explain the HF propagation factor below.
The HF propagation means that we could have (upto) 70 HF mobiles in VK4
being gated by VK3MY and 70 HF mobiles in VK2 being gated by VK5AH-4,
and none of them interferring with each other.  The lack of propagation
becomes an advantage.

So, IMHO, at this stage with the limited number of HF mobiles, I don't
think a beacon at 5 minutes would hurt the network, but being mindful
that as more HF mobiles become active, I agree, then the outcome of
Richard's sums would be implemented.

And just musing, would the HF network handle 200 HF mobiles?  (just
dreaming)

Regards,
Ron
vk3ecv/vk3wrm

> See http://www.aprs.net.au/hf_aprs_information.htm for a Guide to APRS
HF in
> Australasia (Note that this web page is still under construction and
> requires updating)
> 
> Cheers
> Richard
> VK3JFK
> 
> 
> 
> > -----Original Message-----
> > From: ozaprs-bounces at marconi.ics.mq.edu.au [mailto:ozaprs-
> > bounces at marconi.ics.mq.edu.au] On Behalf Of Tony Hunt
> > Sent: Wednesday, 7 July 2004 12:24 AM
> > To: OZ-APRS Mial-list
> > Subject: [OZAPRS] HF Mobile beacon times
> > 
> > Well while we are on the subject of HF operations and all excited it
might
> > be a good idea to check our beacon timings..
> > 
> > I dont know what was decided or discussed last time this came up but
Ive
> > noticed some strange things particularly today..
> > 
> > One station who I will name VK2HL was beaconing at about 30 second
> > intervals.. Now I appologise if this embarrases him/her .. That is not
my
> > intention.. There may be some good reason for this.. I noticed it
> > happening
> > over a pretty long period unfortunately..
> > 
> > As I said sorry if it causes you embaresment but last time someone
didnt
> > want to name someone then we all got left guessing and the discussion
went
> > round in circles for days.. I am not usually a rude person for those
who
> > know me so I have no intention to make trouble.. After all we are all
> > experimenters.. I myself was asked when I was going to stop messing
about
> > at
> > home here with HF beacons..
> > 
> > Ive since gone mobile around the City and Metro areas in range of the
2m
> > system and I am beaconing on HF from the car.. Maybee this could be
said
> > to
> > be stupid by some and I understand.. The arrangment isnt perminent
> > anyway..
> > So I can imagine that 2HL's 30 second beacons are of the same nature..
> > He/She seems to be beaconing from the car but its not moving when we
get
> > these 30 second beacons..
> > 
> > Now if anybody did this in Adelaide on VHF it would be raised in a
> > freindly
> > way probably.. Its just about education basically..
> > 
> > For info I beacon from the car at a rate no faster than about 7 mins
from
> > what I can tell stationary or mobile with Ui-View.. If this is a
problem
> > then I would hope sombody would tell me..
> > 
> > Today I inflickted the network with lots of message frames in the
> > afternoon
> > as a bit of a test.. I never got any ACks back either but thems the
> > breaks..
> > With more and more TinyTrak3's getting on there I guess messaging has
its
> > limitations anyway..
> > 
> > 73 and enjoy Tony Hunt VK5AH
> > 
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> 
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