16 Feb
2000
16 Feb
'00
1:31 p.m.
--- John Wilson <wilson(a)dbit.dbit.com> wrote:
On Wed, Feb 16, 2000 at 06:44:14PM +0000, Tony Duell
wrote:
My younger brother did that as a kid, too. The teacher tapped back "cut it
out" when they tried it during a test.
Hmmm.. I've tried to learn morse several
times, and failed every single
time. I don't know why, but it just doesn't seem to 'click' with me.
Well, having an actual use for it makes it a lot easier to remember. My
best friend and I learned Morse code in 6th grade so that we could pass
notes in class that no one could understand. Naturally that later fizzled,
the 7th grade teacher was a ham and the 8th grade teacher was a radio
operator in the Norwegian underground in WW2, so much for that idea! I *always* wanted to do that, I actually bought a
DUP11 years ago for this
purpose but never dug up documentation on it until recently. You'd need to
build some kind of external clock (PLL really I guess) that synchronized to
the bit transitions of AX.25, shouldn't be a very big deal though.
My knowledge of sync serial comes from years of working with third party
devices on DEC equipment, but here goes... If the DUP-11 has a COM5025
serial chip on it then what it's expecting is something like a "standard"
bit-rate on its input connector. With the right cable, I'd expect to
feed it clocking through pins 15 and 17 on a DB-25 at EIA levels (+/- 12VDC).
We used to have racks of "modem eliminators" that were effectively null-modem
devices that would provide clocks to DTE equipment on both sides. There were
typically various options to set as well, bit rate being chief among them.
Most of ours were set to between 9600 and 56Kbps with a couple set to 64kpbs
and one to 128kbps for reproducing environments of our European customers.
Sync serial has no start bits, no stop bits, just bits. With protocols like
SDLC, there's a "flag byte" of 0x7E (0111 1110) that the receiving hardware
uses to determine the start and stop of a packet. One efficiency of sync
hardware is you aren't trasmitting 10 bits to communicate 8. The downside
is extra hardware on both ends and slightly more expensive cables to send
it all.
If I'm confusing the DUP-11 with other DEC cards that use the COM5025, sorry.
The original Software Results Corp. COMBOARD used that chip because it was
identical to whatever Qbus card we used to use when we were shipping the
HASPBOX (a PDP-11 with sync serial and a DPV-11 to communicate via parallel
to a PDP-11/70 or VAX-11/7xx).
Stupid question: what comes out of the other side of
a ham TNC these days?
It used to be Bell 202 modem tones at 1200 baud HDX, over an FM voice signal,
it *can't* still be that easy though can it?
In the 2 meter band in the U.S., at least, Hams are restricted to 1200 baud.
AFAIK, it is that simple. There are "pocket TNCs" that are little more than
audio modulator circuits that depend on the CPU in your PeeCee to produce
a valid AX.25 bitstream. I've seen it work with an HP-95LX - "pocket
packet".
-ethan
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16 Feb
16 Feb
2:07 p.m.
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2:57 p.m.
On Wed, Feb 16, 2000 at 04:31:51PM -0800, Ethan Dicks wrote:
In the 2 meter band in the U.S., at least, Hams are
restricted to 1200 baud.
No, not exactly. But we are limited to the same bandwidth as an FM
voice channel, so there is a practical limit. 9600 baud fits into the
permissible deviation well enough and is commonly used on 2 meters. (Doing
true FSK rather than an audio simulation of FSK helps minimize the bandwidth
used.) More speed might be possible with the kinds of fancy tricks that
gave us 56K landline modems (and some hams experiment with that kind of stuff).
On 440MHz and above there are some 100khz channels available. For those,
56K is the most popular high-speed mode (but pretty scarce at that). You
need a modem that outputs a 10 meter carrier pre-modulated with the signal,
and a transverter to get from there to the desired frequency; so that makes
it expensive (~$1000 to fully equip a station with new equipment) and
that's why it's not really common IMO. There have also been experiments
with 2 and 10 mbps microwave links using gunn diode transceivers and
ethernet cards and slower network cards. And now that spread-spectrum
is wide open for experimentation without any STA's required, I expect
that to be the next hotbed of activity. Most or all of the no-license-required
wireless ethernet devices operate in ham bands (we have to share the
bandwidth with them), so it's possible and legal to use high-gain antennae
and perhaps bigger power amps to use that kind of equipment for long-
distance links. The new regs require dynamic control of output power
though - you can't output any more power than is necessary to maintain
the link, and the control of it must be automated.
But so far the fastest I'm doing is 9600 baud (on 2 meters).
--
_______ http://www.bigfoot.com/~ecloud
(_ | |_) ecloud(a)bigfoot.com finger rutledge(a)cx47646-a.phnx1.az.home.com
__) | | \__________________________________________________________________
6:13 p.m.
Hi Folks:
56K packet has been running the Vancouver area for over 5 years. We have
two repeaters and a third waiting to be installed. It's on the 70 cm band.
It's a TCP/IP network, UNIX based, and fully interconnected to the Internet.
Kevin
At 06:57 PM 00/02/16 -0700, you wrote:
On Wed, Feb 16, 2000 at 04:31:51PM -0800, Ethan Dicks
wrote:
> In the 2 meter band in the U.S., at least, Hams are restricted to 1200
baud.
No, not exactly. But we are limited to the same bandwidth as an FM
voice channel, so there is a practical limit. 9600 baud fits into the
permissible deviation well enough and is commonly used on 2 meters. (Doing
true FSK rather than an audio simulation of FSK helps minimize the bandwidth
used.) More speed might be possible with the kinds of fancy tricks that
gave us 56K landline modems (and some hams experiment with that kind of
stuff).
On 440MHz and above there are some 100khz channels available. For those,
56K is the most popular high-speed mode (but pretty scarce at that). You
need a modem that outputs a 10 meter carrier pre-modulated with the signal,
and a transverter to get from there to the desired frequency; so that makes
it expensive (~$1000 to fully equip a station with new equipment) and
that's why it's not really common IMO. There have also been experiments
with 2 and 10 mbps microwave links using gunn diode transceivers and
ethernet cards and slower network cards. And now that spread-spectrum
is wide open for experimentation without any STA's required, I expect
that to be the next hotbed of activity. Most or all of the
no-license-required
wireless ethernet devices operate in ham bands (we have
to share the
bandwidth with them), so it's possible and legal to use high-gain antennae
and perhaps bigger power amps to use that kind of equipment for long-
distance links. The new regs require dynamic control of output power
though - you can't output any more power than is necessary to maintain
the link, and the control of it must be automated.
But so far the fastest I'm doing is 9600 baud (on 2 meters).
--
_______ http://www.bigfoot.com/~ecloud
(_ | |_) ecloud(a)bigfoot.com finger rutledge(a)cx47646-a.phnx1.az.home.com
__) | | \__________________________________________________________________
---
Kevin McQuiggin VE7ZD
mcquiggi(a)sfu.ca
6:48 p.m.
On Wed, Feb 16, 2000 at 09:13:56PM -0800, Kevin McQuiggin wrote:
56K packet has been running the Vancouver area for
over 5 years. We have
two repeaters and a third waiting to be installed. It's on the 70 cm band.
It's a TCP/IP network, UNIX based, and fully interconnected to the Internet.
I know, that network is the envy of most other places.
--
_______ http://www.bigfoot.com/~ecloud
(_ | |_) ecloud(a)bigfoot.com finger rutledge(a)cx47646-a.phnx1.az.home.com
__) | | \__________________________________________________________________
9:05 p.m.
On Wed, Feb 16, 2000 at 06:57:47PM -0700, Shawn T. Rutledge wrote:
No, not exactly. But we are limited to the same
bandwidth as an FM
voice channel, so there is a practical limit. 9600 baud fits into the
permissible deviation well enough and is commonly used on 2 meters. (Doing
true FSK rather than an audio simulation of FSK helps minimize the bandwidth
used.)
Wait, 9600 baud in an audio channel using FSK?!?!?! I failed almost every
course I ever took but I coulda sworn there was some rule that you couldn't
get more BPS than half the channel width with FSK? What are the tone freqs
(and which is which, does the L.S.M.F.T. rule still apply?)?
John Wilson
D Bit
8900
days inactive
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days old
5 comments
5 participants
participants (5)
-
ard＠p850ug1.demon.co.uk -
ethan_dicks＠yahoo.com -
mcquiggi＠sfu.ca -
rutledge＠cx47646-a.phnx1.az.home.com -
wilson＠dbit.dbit.com