[Vk1tac] Ginini 2 metre services

[Neil Pickford]

-------- Original Message --------
Subject: Fw: Ginini 2 metre services
Date: Fri, 17 Jan 2003 14:48:47 +1100
From: "Mr Gilbert Hughes" <ghughes3@bigpond.com>
To: "Richard Elliott" <richard.elliott@dfat.gov.au>,"Paul Elliot"
<pkbelliot@bigpond.com>, "Paul Bell" <paul.bell@afp.gov.au>,"Neil
Pickford" <neilp@goldweb.com.au>,"Keith Malcolm"
<kmalcolm@tpg.com.au>,"John Woolner" <johnwoolner@auslig.gov.au>,"Mike
Dower" <vk1eng@tpg.com.au>


More earlier thoughts
Regards
Gilbert Hughes
mailto:ghughes3@bigpond.com

----- Original Message -----
From: "Owen Duffy" <owen@oda.com.au>
To: "Mr Gilbert Hughes" <ghughes3@bigpond.com>
Cc: <paul.bell@afp.gov.au>
Sent: Monday, 13 January 2003 11:30 AM
Subject: RE: Ginini 2 metre services


> Gil, some thoughts below instream:
>
> >===== Original Message From "Mr Gilbert Hughes"
<ghughes3@bigpond.com> =====
> >(Could one of you please forward this to Karl Makin - I do not have
his
> >address)
> >
> >Following the installation of the new tower there is a much greater
> >isolation (about 70 dB compared to 30 odd dB on the old tower)
between
> >the new Tx and Rx antennas.
> >
> >In order to save floor space (and cavity resonators) we can re-work
the
> >2 metre multi-coupling (currently 14 cavities) to make it easier to
fit
> >the Ginini 70 cm hub of the linked repeater project, and the 6 metre
> >repeater diplexer (modified 70 MHz cavities) and the 2 mtr and 70 cm
Rx
> >voting equipment.
> >
> >This has causes us to think about what 2 mtr services we really want
to
> >have on the site.
> >
> >Some thoughts are:
> >
> >1. Only two 2mtr services can easily be engineered eg voice and
packet.
> >
> >2.  Does the current usage of the 4800 baud packet justify continuing
> >the service - (or move it to Bulls head??)
> >
> >3. An APRS wide has been suggested, however we understand that a wide
> >coverage store and forward service could do more harm than good if
APRS
> >continues to gain in popularity and more 'wides' are installed.
> >
> >4. Is there any advantage to packet users of making the site a 1200
baud
> >hub? (we understand that the answer is no for a number of reasons.)
> >
> >Does the 2 mtr packet currently  get much use now?
> >
> >Is the usage likely to decline even further?
> >
>
> I ran up a packet station a couple of years ago, and was interested in
> determining why throughput was so bad on the 2m 1200Baud and 4800 Baud
> channels, and exploring ways to improve the situation. The following
comments
> on packet relate to observations at that time.
>
> The 4800Baud channel was quite congested, which was the prime reason
for poor
> throughput. The mode of operation of the repeater may have exacerbated
that.
> In a scenario where most stations using the repeater could not hear
each
> other, there is a high probability of collisions which wastes
bandwidth. This
> problem becomes worse at high utilisation levels where collisions
result in a
> snowball effect.
>
> It is interesting to drill down on what constitutes the traffic. My
> observations were that it is mainly machines talking to machines in a
batch
> oriented mode (eg node list transfers, network management, large file
> transfers often of material that is shareware and one might argue is
has a
> pecuniary aspect and should not be transmitted by amateur networks).
The
> traffic has grown to a point where the congestion renders the medium
generally
> unsuited to intereactive traffic, and even email (where in my
experience, it
> would take 1 to 3 days to get a message to a mailbox in the
Netherlands).
>
> Interestingly, the example I quote above was one where I was
collaborating
> with a person in the Netherlands re changes to fix bugs in some packet
> software... but the packet network could not provide a reasonable
> communications service to support its own development - we had to move
to
> Internet email.
>
> My recollection is that Dave Thomson, in one of his fits of
frustration with
> batch transfers spoiling their digi, tore it down.
>
> I formed the view that packet activity was mostly about establishing
networks
> without any clear objectives of what service the network could
provide, and
> that network overheads and mindless use rendered the networks unusable
for
> interactive traffic and email. Further, there is considerable
resistance to
> change or experimentation.
>
> BTW, the 70cm digi at Ginini was almost unused. The best performing
(most
> consistent and highest througput) path from my QTH to VK1BBS was up to
Ginini
> on 70cm, across to the 4800 node, and down to VK1BBS. Even when the 2m
4800
> channel was very busy and gave hopelessly low thoughput to stations on
2m, it
> was possible to get 'priority' access to the 2m node via the 70cm
node.
>
> It seems to me that in 15 years, there has been little progress in
packet in
> this country.
>
> APRS, although using packet protocols (AX.25), albeit in a limited
way, is
> more about transmitting packets (in a broadcast mode) without
apparently much
> regard to whether they are received anywhere of use. My experience is
that
> success rates are low, caused again in part by congestion, and
incorrectly
> aligned transmitters.
>
> My though is that wanting to increase the number of WIDE nodes that
are heard
> in a community increases congestion. So whilst simple thinking is that
lots of
> WIDES and RELAYS increase the change of a position report being heard
> somewhere usefull, increased traffic causes congestion and decreases
the
> probability that a position report is not clobbered by another
(hidden)
> station.
>
> My suggestion is that before committing resources to a network of
digis in an
> adhoc fashion, that some service levels be considered, the traffic
modelled,
> and that the models be validated with some controlled field trials.
>
> Back to Ginini, the 2m voice repeater seems to get less use as time
passes. I
> suspect that is part of the changing amateur community that we don't
> understand very well. Indeed, I see signs that the linked repeaters
seem to
> get less use the more widespread the linking - perhaps users preferred
the
> 'local' context.
>
> If the moves that I understand are under way to downgrade the
qualification
> requirements for amateur radio (step 1: foundation licence, step 2:
coerce the
> multiple classes of licence to a single class based on the foundation
licence)
> to bolster numbers of licencees (and hopefully active operators),
there may be
> considerable growth in demand on the facilities like 2m repeaters that
offer
> much better service than the CB repeaters.
>
> >Would the regular users agree to either move the service to Bulls
Head,
> >or close it down?
> >
>
> As noted earlier, my experience of a couple of years ago was that
there is
> considerable resistance to change in the packet network.
>
> Note that a number of modern transceivers come with 1200 and 9600
packet
> modems built in. When I looked around a couple of years ago, the
original HAPN
> (4800) modems had been discontinued by the Vancouver group. I am not
aware of
> any transceivers with an integrated HAPN (4800) modem. I suspect that
it may
> be easier to get on 9600 packet than 4800, but the shared
infrastructure is
> supports 4800. The ready availability of both TNCs and transceivers
with
> integral TNC with 9600 support is a factor that perhaps ought be
considered
> when planning future packet resources.
>
> The way ahead might be to continue the 4800 service at Bulls Head, but
to
> incorporate a 9600 node as well.
>
> It is hard pleasing all of the people all of the time Gil!
>
> Owen
>
> BTW, I have carefully avoided recommending in favour or against any of
the
> services, but put on paper some thoughts on some of the factors that
might be
> considered in your deliberations. I hope they are of use.
>
>
> >Lets have an exchange of views as a first step.
> >
> >Regards
> >Gilbert Hughes
> >mailto:ghughes3@bigpond.com
>
> --
> ===================================================
> Owen Duffy  (owen@oda.com.au)
> Phone:  +61 2 6257 3872            (02) 6257 3872
> Mobile: +61 417 408 424            0417 408 424
> ===================================================
>
>