[OZAPRS] Higher beacon rate HF versus VHF?

[Geoff]

10 minutes for normal stations, however the PRIMARY NET STATION should
beacon more often, to give everyone else a reference to tune to.
I think we had defined the primary and secondary net stations to beacon
every 5 minutes.

On 30m we already have these established (Richard/Ray please correct me if
I'm wrong)
Primary = VK3MY-4
Secondary = VK4DMI-4

On 40m and now 20m we need to work out who will be running a 24x7 HF Gate on
these bands and allocate NET roles accordingly....

Regards,
Geoff

> -----Original Message-----
> From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
> Behalf Of Richard Hoskin
> Sent: Monday, 30 March 2009 8:01 PM
> To: 'Australian APRS Users'
> Subject: RE: [OZAPRS] Higher beacon rate HF versus VHF?
> 
> 
> 
> Hi All,
> 
> Remember on HF you are sharing this band with all other APRS users world
> wide and even though you can not hear them they may hear you. (You just
> have
> to look at some of the posts on this list from HF APRS operators in other
> countries for evidence of this). Also 300 baud is 1/4 the speed of VHF
> APRS
> which means you can only fit 25% of the stations on the channel if you use
> the same beacon rate.
> 
> Lets see, HF APRS increases the coverage area from roughly 200,000 Sq Km
> using 3 hops to potentially 75 Million SQ KM. An increase in coverage area
> of 375 times. At 300 baud you get a reduction in band capacity of 4 times.
> 
> Leaving your beacon rate the same as for VHF or increasing it some what
> really doesn't make a hole lot of sense.
> 
> 
> That's why the world wide recommended minimum APRS beacon rate for HF is
> 10
> minutes or more.
> 
> Or another way to look at it; 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.
> 
> Cheers
> Richard
> VK3JFK
> 
> > -----Original Message-----
> > From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
> > Behalf Of Jack Chomley
> > Sent: Monday, 30 March 2009 6:45 AM
> > To: Australian APRS Users
> > Subject: Re: [OZAPRS] Higher beacon rate HF versus VHF?
> >
> > At 11:00 PM 3/29/2009, you wrote:
> > >Jacks success at being received by my HF iGate with 600mW, complaints
> > >about QRM etc got me thinking about beacon rates for HF vs VHF.
> > >
> > >Given the low number of HF stations, the vastness of Australia, the
> > >vagaries of HF and the fact that HF stations do not digipeat to HF,
> > >and perhaps if I go on, shouldn't digipeat to VHF, I believe beacon
> > >rates on HF should be higher than on VHF. What do others think?
> > >
> > >David
> > >VK4MDX
> >
> > David,
> > I have been using a beacon rate of 2 minutes on my motorcycle system
> > running 6 watts on 30m with an Icom 703, SCS DSP TNC, Garmin
> > 16-HVS  GPS.  The performance has been good over the last 12 months,
> > many of the beacons were missed, but I put that down to the low power
> > and antenna waving around while mobile.
> > Back in January, I changed the transmit format of the APRS data
> > frames to the compressed format and my "hit" rate immediately went
> > up. Probably because of the shorter packets, meant less chance of
> > them being corrupted.
> > See my Jan 15th '09 track log....
> > http://aprs.fi/?call=VK4JRC-15&dt=1231977600&mt=m&z=11&timerange=3600
> > Since the hit rate has gone up, I can now lower the beacon rate and
> > still get a good track record.
> > Bike here:
> > http://www.radiotelemetry.net/html/hf_mobile_aprs.html
> > Personally, I think that IF there are enough IGATES, there is
> > probably no reason to have a high beacon rate, nor need to run
> > anymore than about 20 watts, but the secret of success is to use
> > compressed format APRS data.
> > Yesterdays test also proved that when there was QRM on the frequency,
> > I managed to get some hits in between the contest stations, that were
> > just off the 40m frequency. Shorter frames, less chance of corruption ;-
> )
> > My antenna for yesterday's test was a Buddipole vertical, setup on an
> > 8ft tripod, in the back yard, the counterpoise was 1 electric fence
> > wire above ground radial, deployed towards the South. The vertical
> > element a Versa-T,  1 arm section, coil, with 5 section shock-corded
> > military whip, on top of the coil.
> > See Buddipole:
> > http://www.buddipole.com/
> >
> > 73  Jack VK4JRC
> >
> >
> >
> >
> >
> > _______________________________________________
> > Ozaprs mailing list
> > Ozaprs at aprs.net.au
> > http://aprs.net.au/mailman/listinfo/ozaprs
> 
> _______________________________________________
> Ozaprs mailing list
> Ozaprs at aprs.net.au
> http://aprs.net.au/mailman/listinfo/ozaprs

_______________________________________________
Ozaprs mailing list
Ozaprs at aprs.net.au
http://aprs.net.au/mailman/listinfo/ozaprs