[OZAPRS] HF Mobile beacon times

Richard Hoskin vk3jfk at amsat.org
Wed Jul 7 08:38:20 EST 2004

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
increases. You just need to do the sums.

An average length APRS Posit packet takes 3 to 4 seconds to transmit on
Assuming a channel efficiency of 30% for ax25 this results in a maximum of
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
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
the channel. HF Propagation is also an important factor in limiting

See http://www.aprs.net.au/hf_aprs_information.htm for a Guide to APRS HF
Australasia (Note that this web page is still under construction and
requires updating)


> -----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
> 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
> 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
> 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
> 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
> 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
> limitations anyway..
> 73 and enjoy Tony Hunt VK5AH
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