http://www.uspacket.org/mixmode.htm

Charles Brabham, N5PVL

On Wed, 12 Jan 2005 02:30:16 +0000, Charles Brabham wrote:

http://www.uspacket.org/mixmode.htm

Charles Brabham, N5PVL

This is rather interesting information for use on repeaters that welcome
mixed mode, but using it on what is intended as a voice repeater would
welcome ill will, and perhaps retaliation, or complaints of deliberate
QRM. Where the repeater operators concur, it sounds cool.

Hi Charles..

Some comments on your article.

- Using a voice repeater is in a sense like using a bit regenerative
device albeit with no intelligence. The great thing about it is that it
avoid the hidden transmitter problem as repeaters are often built in
high places. Straight digi's or popular nodes on top of hills get messed
up really quickly when one station cant hear another and transmits on
top of them. We use to have a system in NSW that was continually getting
into packet crash problems because it was badly designed. With one user
at each end of the circuit it was great but anymore than that and it was
an abject failure.
- I would suggest that the repeater stays on during both sides of the
data exchange. This means that you only need to have a large txdelay
once and then almost none at all while the exchange is going on. You
will of course have to have a CTS squelch that works not on channel
quieting but on audio or a partial decode of the start framing sequence
- Long PACLENs will always help provided there is little or no dropout
(ie a good strong signal). Large MAXFRAMEs wont really help at all
though if you keep the repeater running.
- If you want to keep keying the repeater on and off think about a
PACLEN way in excess of what is common. I use to run 768 bytes in kiss
mode on a TNC2 box (Using KA9Q NOS) with MAXFRAME 7. At 1200bps I use to
get about 120cps with the TX being keyed up for 30-40 seconds at a time.
- Obviously one has to allow for the repeater timeout and restart. I
dont know the regulations over there but perhaps you can keep it
transmitting data as long as you like. I also wonder what a mess the
repeater access tone will make of the data.
- Using a voice repeater is also something that would work well for
RDFT/Wyman multicast you have already mentioned. I keep hearing that a
faster implementation (wider b/w) is due and since the protocol is being
written even now it may be worthwhile figuring a way to use repeaters.
- If you want to use NewPSK it is worthwhile making the Tunelength close
to zero. Since you are using FM there is no real frequency error to
worry about. I'd also fiddle with increasing the bit rate on an FM
channel (2500 works for an SSB one) (I assume that the W32 soundmodem
version of Tom Sailor's code has that adjustable. It is on the Linux
version)

Tnxs for your article

Bob VK2YQA

Charles Brabham wrote:
http://www.uspacket.org/mixmode.htm

Charles Brabham, N5PVL

Howdy, Bob!

"Bob Bob" wrote in message
...
Hi Charles..

Some comments on your article.

- Using a voice repeater is in a sense like using a bit regenerative
device albeit with no intelligence. The great thing about it is that it
avoid the hidden transmitter problem as repeaters are often built in high
places. Straight digi's or popular nodes on top of hills get messed up
really quickly when one station cant hear another and transmits on top of
them. We use to have a system in NSW that was continually getting into
packet crash problems because it was badly designed. With one user at each
end of the circuit it was great but anymore than that and it was an abject
failure.

That sounds like a job for DAMA, which gets you past the dubious idea of
having all Packet ops at high power in the forlorn hope that they will all
be able to hear each other.

There is danger of a collision while connecting to the DAMA capable node,
but none after that as your station will not transmit therafter until the
node polls it, giving it an OK to do so. Everybody waits their turn, be they
near or far, powerful or QRP.

Since user stations no longer have to hear each other in order to access the
network, then low powered stations using yagis can be set up for network
access with little or no hidden transmitter - related problems. - You can
then attract more users because it's easier and less expensive to
participate, not to mention the fact that it will all work much better.

Most TNC's have DAMA capability built-in, and some soundcard Packet stuff
has it. The free PC-FlexNet node system offers DAMA access as an option.
Switching over to FlexNet with DAMA access would magically cure your Packet
network's ills, and improve its performance in other areas at the same time.

As with any change, a few will be inconvenienced and its up to their fellow
hams to soften the blow by giving them a hand... Kind of like installing a
tone board for a guy with an old VHF rig who can't get on the repeater. The
price for improved performance would include some promotion and legwork,
visiting hams who need help using DAMA access.

DAMA access is used extensively in Europe, where Packet never really lost
its popularity. It's hardly ever been used here in the US...

- I would suggest that the repeater stays on during both sides of the data
exchange.

That sounds very interesting! I'll try to find out if I can get it to fly,
as that would open up the possibility of speeding things up significantly,
as you say. It's sure worth a try.

Charles, N5PVL

Know why didnt I think of that? grin I had never ever heard of DAMA
but it seems so simple. Of course it would rely on everyone using the
same system!

We use to have a ROSE "backbone" all using the one frequency over 3-4
hops. It worked okay if a BBS at one end was forwarding to one at the
other end but if any users wanted to jump in the whole lot came to a
screaming halt.

I'll have to check if the Linux AX25 implementation has DAMA available..
Cant imagine I'll get back into packet until I move though. Have you by
any chance come accross any webpages that cover East Texas? I have seen
bits of the Arkansas network and around Austin but not up around
Longview/Tyler.

Cheers Bob VK2YQA



Charles Brabham wrote:
Howdy, Bob!

"Bob Bob" wrote in message
...

Hi Charles..

Some comments on your article.

- Using a voice repeater is in a sense like using a bit regenerative
device albeit with no intelligence. The great thing about it is that it
avoid the hidden transmitter problem as repeaters are often built in high
places. Straight digi's or popular nodes on top of hills get messed up
really quickly when one station cant hear another and transmits on top of
them. We use to have a system in NSW that was continually getting into
packet crash problems because it was badly designed. With one user at each
end of the circuit it was great but anymore than that and it was an abject
failure.


That sounds like a job for DAMA, which gets you past the dubious idea of
having all Packet ops at high power in the forlorn hope that they will all
be able to hear each other.

"Bob Bob" wrote in message
...

I'll have to check if the Linux AX25 implementation has DAMA available..
Cant imagine I'll get back into packet until I move though. Have you by
any chance come accross any webpages that cover East Texas? I have seen
bits of the Arkansas network and around Austin but not up around
Longview/Tyler.


I'm pretty sure that XNET offers DAMA access, as it generally emulates
FlexNet with the addition of a few additional features. I don't keep up with
the XNET news, but I'm sure there is a Linux version of XNET. I've been
warned that XNET is buggy - but I haven't taken the time to confirm or deny
any of that. In fact, my last experience with XNET was several years ago and
what I did back then set it up and verify that it worked. I didn't really
give it much of a workout on the air, so I can't tell you much about that.
If it does a good job of emulating Flexnet, it should be an outstanding
performer.

I know there is some packet activity in East Texas, but none of those guys
have a web-site about what they do - at least not that I've been able to
find.

I live in the extreme southern tip of Texas, and on "band opening" days when
I can bridge the gap up to the Corpus/Sinton area it is then possible to
node-hop all the way up the gulf coast into Lousianna and then Arkansas.
Part of that routing passes through the area you mentioned, I believe.

Charles, N5PVL

Tnxs Charles

So if you see any packets from me in a few months dont get excited...
I'll probably be using my VK callsign for a few years when I move
(Pretty sure the FCC says thats okay)

Cheers Bob VK2YQA

Charles Brabham wrote:
I'm pretty sure that XNET offers DAMA access, as it generally emulates
FlexNet with the addition of a few additional features. I don't keep up with
the XNET news, but I'm sure there is a Linux version of XNET. I've been
warned that XNET is buggy - but I haven't taken the time to confirm or deny
any of that. In fact, my last experience with XNET was several years ago and
what I did back then set it up and verify that it worked. I didn't really
give it much of a workout on the air, so I can't tell you much about that.
If it does a good job of emulating Flexnet, it should be an outstanding
performer.

I know there is some packet activity in East Texas, but none of those guys
have a web-site about what they do - at least not that I've been able to
find.

I live in the extreme southern tip of Texas, and on "band opening" days when
I can bridge the gap up to the Corpus/Sinton area it is then possible to
node-hop all the way up the gulf coast into Lousianna and then Arkansas.
Part of that routing passes through the area you mentioned, I believe.

Charles, N5PVL

"Charles Brabham" wrote in message
om...

"Bob Bob" wrote in message
...

I'll have to check if the Linux AX25 implementation has DAMA available..
Cant imagine I'll get back into packet until I move though. Have you by
any chance come accross any webpages that cover East Texas? I have seen
bits of the Arkansas network and around Austin but not up around
Longview/Tyler.


I'm pretty sure that XNET offers DAMA access, as it generally emulates
FlexNet with the addition of a few additional features. I don't keep up
with
the XNET news, but I'm sure there is a Linux version of XNET. I've been
warned that XNET is buggy - but I haven't taken the time to confirm or
deny
any of that. In fact, my last experience with XNET was several years ago
and
what I did back then set it up and verify that it worked. I didn't really
give it much of a workout on the air, so I can't tell you much about that.
If it does a good job of emulating Flexnet, it should be an outstanding
performer.

Yes, (X)NET offers DAMA. We used it years ago on a dual-speed 1200/9600 user
access port to prevent collisions because TNCs cannot detect transmissions
not using their own speed. Of course there's a certain protocol overhead but
DAMA performed fine. We abandoned it after the majority of users migrated to
9600. We ran (X)NET Linux in our PBBS for many years. Extremely robust,
sysop maintenance work was virtually zero. Still running (X)NET DOS in our
local digipeater. BTW, there's an (X)NET forum accessible via
http://www.swiss-artg.ch/xnet/index.html although it seems to be down
currently.

Markus HB9BRJ