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PA2AGA > HDDIG 25.09.99 02:23l 192 Lines 7891 Bytes #-9767 (0) @ EU
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Subj: HamDigitalDigest 99/239D
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From: pa2aga
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Subject: HamDigitalDigest 99/239D
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>about 25 miles. 25W, 10 el yagis on both ends. Works well,
>even though we are way out of the first Fresnel zone.
>
>> You need a BER of under 1 in 10E6 or your network
>> performance becomes dismal out past 3 or 4 hops.
>> That means you have to engineer things *right* on
>> every link.
>
>Not possible. We have these hills and mountains.
>The 100 mile link to the south works very very well.
>However that link of 25 miles to the north would take
>three relay points to make it line of sight. Oops.
Yeah, and if the two hops were linked as part of a network path,
all the traffic traversing that part of the net would be limited by the
BER of the worst link in the path. That's why you can't have bad
paths in your network. They kill more than just the one hop's
performance. They drag down a large segment of the network's
traffic along with them.
What you can do is break the network at such bad locations,
forming multiple smaller networks. You can then internet them
using routing topologies that avoid the bad link *if the overall
topology is sufficiently redundant to avoid having any one critical
path*. The total path from any station to another may then be longer,
but it won't be flaky, and only users who need to bridge between
those segments at the moment are impacted. OTOH if you let
those marginal, flaky, and slow paths into your network, the whole
network suffers.
The problem is, we often aren't thick enough on the ground to
provide those alternate routes. So our dream of a coherent
national network founders and we have to be satisfied with a
bunch of smaller disjoint networks. We may be able to gateway
between some of these disjoint networks on an intermittant or
very limited basis, but we can't tie them into a coherent national
level network on a 24x7 basis.
Gary
Gary Coffman KE4ZV | You make it |mail to ke4zv@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
>.
------------------------------
Date: Wed, 22 Sep 1999 12:38:22 -0400
From: Gary Coffman <ke4zv@bellsouth.net>
Subject: Let's look at real numbers for TNC software sales
On Mon, 20 Sep 1999 20:02:33 -0700, "Hank Oredson" <horedson@att.net> wrote:
>Gary Coffman <ke4zv@bellsouth.net> wrote in message
>> Alligator thinking. Just being loud doesn't cut it. The
>> key factor is the ability to receive a clean signal.
>
>Not always an option.
Then that path isn't an option as part of a larger network.
>> That requires a clean path, or your BER goes through
>> the roof due to multipath induced intersymbol distortion.
>> (SS has the potential of helping significantly with that,
>> but we don't have any off the shelf SS equipment for
>> amateur use right now, and there are other problems
>> with SS systems co-located on high RF sites that I
>> expect will be difficult to resolve.)
>
>Nice idea, but not always an option.
Actually, it isn't an option at all right now for Part 97
use. The only SS equipment available that's up to the
job is commercial equipment designed for other
services. There are a host of problems to be overcome
before SS will play a role in amateur packet networks
as anything other than a novelty.
>> We tried 50 and 100 watt amplifiers early on. Didn't
>> help. We could *hear* the alligators, but the BER was
>> so bad that they degraded the performance of the
>> entire network.
>
>Our experience is quite different. Without the high ERP,
>we had NO LINK AT ALL.
Better no link at all than a degraded network. If you're
going to talk about large scale networks, you've got to
look beyond the end of your own nose and consider the
impact your poor link may be having on other parts of
the network.
>> >Takes aluminium as well as silicon.
>> >The only other choice is to use the internet.
>> >That ain't ham radio. No challenge involved.
>>
>> The other choice is to not succumb to alligator thinking,
>> and instead do the hard RF path engineering to make
>> the system work. It is hard work, it does require a lot of
>> resources, but that's how it is done. AT&Tdid it many
>> years ago with their RF relay network. If we want the
>> same RF network capabilities, we have to repeat what
>> they did. Physics hasn't changed.
>
>I simply do not agree. There are not resources enough to
>bridge the long hauls using short hops. The money ain't
>there. So it is better to do SOMETHING rather than
>throw up one's hands and claim it cannot be done because
>it cannot be done "perfectly".
Half-assed is still half-assed. Squandering our scarce resources,
people, and community support on systems we *know* can never
perform at a satisfactory level is worse than foolishness. It actively
damages our chances of doing the sorts of things we *can* do well.
>> Grandiose fast amateur RF networks spanning thousands
>> of miles are just a pipedream for any group with less resources
>> than AT&T. We can't fund it, we can't build it, we can't maintain it,
>> and we can't manage it. We don't have the resources or the cooperative
>> spirit to do it purely on amateur radio. There are too many square miles
>> and too few hams standing on them in the US to allow that to happen.
>
>Nonesense. It COULD be done, but not with the "I need a relay
>point every few miles" or "The BER must be perfect" thinking.
Perhaps you'd care to enlighten us how it "COULD be done".
Remember that "it" is a fast coherent national level packet
switched network capable of handling the sorts of applications
which have currently pulled our user base away from packet
radio and on to the wired internet.
Gary
Gary Coffman KE4ZV | You make it |mail to ke4zv@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
>.
------------------------------
Date: Wed, 22 Sep 1999 12:40:17 -0400
From: Gary Coffman <ke4zv@bellsouth.net>
Subject: Let's look at real numbers for TNC software sales
On Mon, 20 Sep 1999 20:02:33 -0700, "Hank Oredson" <horedson@att.net> wrote:
>Gary Coffman <ke4zv@bellsouth.net> wrote in message
>> Perhaps in the densely populated little nations of Europe national
>> networks can be done, but not across our vast rural spaces. That's
>> sad, but it is real. We need to face up to reality and do what we are
>> best suited to do, and that is the smaller scope metropolitan and
>> relatively small regional networks that we can practically fund,
>> build, and maintain.
>>
>> The GRAPES network covers an area of roughly 45,000 square
>> miles, and that's about as big as is practical for a fast amateur
>> network in our part of the US. We don't have the people, money,
>> or sites to grow it much bigger. California might be different. They
>> have 10 times our population, and a bunch of natural high sites. I
>> haven't seen an organization with the energy and dedication of
>> GRAPES building a fast network out there, however.
>
>California is mostly open space with no people, just like the rest
>of the West. It's a BIG place. The big cities are, north to south,
>with approximate distances:
>
>Vancouver, BC - Seattle, WA - 50 miles.
>Seattle, WA - Olympia/Tacoma, WA - 50 miles.
>Olympia/Tacoma, WA - Portland, OR - 100 miles.
>Portland, OR - San Francisco, CA - 600 miles.
>etc.
My, my, how California has grown. My atlas says that of those
cities, only the latter is in California. :-)
Most of the population of California is arranged linearly down
To be continued in digest: hd_99_239E
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