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PA2AGA > HDDIG 01.10.00 18:56l 210 Lines 7432 Bytes #-8644 (0) @ EU
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Date: Thu, 28 Sep 00 22:09:57 MET
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Ham-Digital Digest Thu, 28 Sep 2000 Volume 2000 : Issue 265
Today's Topics:
Algorithm for decoding RTTY (Linux project) (5 msgs)
APRS Operating Question (6 msgs)
Compression et all
Porche Boxter or Luxury Cruise Earn $$$ In Days This Works!!!
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Loop-Detect: Ham-Digital:2000/265
----------------------------------------------------------------------
Date: Wed, 27 Sep 2000 12:58:10 GMT
From: magne@radar.no (Magne Mæhre)
Subject: Algorithm for decoding RTTY (Linux project)
I was thinking about writing an RTTY modem for Linux, using the
sound card (/dev/audio) interface (since I can't seem to find something
like this out there). Not being a DSP guru, I'd like to present some
thoughts..
1. Detector
I guess the approach with adding the input signal with predefined
waveforms (0 and 90 degrees for each of the two frequencies),
and then passing it through an integrate-and-dump (as
described in Tom McDermott's book) is ok ?
What would be a suitable integration time? 8 integrations pr. bit,
perhaps? (to allow for adjusting to match edges better)
2. Decoder
One alternative is to shift the detector output into a shift-register,
and look for something that matches a valid Baudot character.
Are there better methods ?
Any comments?
--Magne / la1bfa
(trying to learn something here :)
------------------------------
Date: 27 Sep 2000 14:19:09 GMT
From: Hans-Peter Zorn <hpz@gmx.net>
Subject: Algorithm for decoding RTTY (Linux project)
Magne Mæhre <magne@radar.no> wrote:
> I was thinking about writing an RTTY modem for Linux, using the
> sound card (/dev/audio) interface (since I can't seem to find something
> like this out there). Not being a DSP guru, I'd like to present some
> thoughts..
[...]
> Any comments?
If you need some example sourcecode for rtty, amtor and pactor using
soundcard linux, look at:
http://www.ife.ee.ethz.ch/~sailer/ham/linux/hf.html
Does not compile out of the box on current systems, however. You
need to use the userland implementation of hf_kernel and tweak
with some assembler code current gcc seem to have problems with.
-hp
--
Hans-Peter Zorn, Karlsruhe, Germany
http://www.stud.uni-karlsruhe.de/~uhsm/ hpz@gmx.net (preferred)
http://1409.org/people/hp/ hp@1409.org (hamradio stuff)
------------------------------
Date: Wed, 27 Sep 2000 14:49:16 GMT
From: nomail@rob.knoware.nl (Rob Janssen)
Subject: Algorithm for decoding RTTY (Linux project)
Magne Mæhre <magne@radar.no> wrote:
>I was thinking about writing an RTTY modem for Linux, using the
>sound card (/dev/audio) interface (since I can't seem to find something
>like this out there). Not being a DSP guru, I'd like to present some
>thoughts..
The DSP part of this is already in the kernel, and accessible via
/dev/hfmodem. It can be enabled in the configuration when needed.
I don't know what userprogram supports this device, there is no
documentation in the sourcecode... it only says it was written by Thomas
Sailer (sailer@ife.ee.ethz.ch).
Rob
--
+----------------------------------+--------------------------------------+
| Rob Janssen pe1chl@amsat.org | WWW: http://www.knoware.nl/users/rob |
| AMPRnet: rob@pe1chl.ampr.org | AX.25 BBS: PE1CHL@PI8WNO.#UTR.NLD.EU |
+----------------------------------+--------------------------------------+
------------------------------
Date: 27 Sep 2000 15:46:34 GMT
From: Hans-Peter Zorn <hpz@gmx.net>
Subject: Algorithm for decoding RTTY (Linux project)
Rob Janssen <nomail@rob.knoware.nl> wrote:
> Magne Mæhre <magne@radar.no> wrote:
>>I was thinking about writing an RTTY modem for Linux, using the
>>sound card (/dev/audio) interface (since I can't seem to find something
>>like this out there). Not being a DSP guru, I'd like to present some
>>thoughts..
> The DSP part of this is already in the kernel, and accessible via
> /dev/hfmodem. It can be enabled in the configuration when needed.
> I don't know what userprogram supports this device, there is no
> documentation in the sourcecode... it only says it was written by Thomas
> Sailer (sailer@ife.ee.ethz.ch).
As far as I know the kernel part will disappear in future linux
version because it is hard to maintain and only supports very
few soundcards. At Thomas' site you find 3 parts: the DSP-stuff
as kernel-land implementation (hfkernel_kernel), the DSP things
for usermode (hfkernel_user) and the terminal itself. You need
either ther usermode hfkernel or the kernelmode hfkernel. The
double meaning of "kernel" is a little confusing in this case...
The usermode kernel uses the standard linux sounddrivers and
should work with current hardware where the hfkernel_kernel
only supports ISA Soundblaster compatible cards with aren't
manufactured any more. You have to apply a patch for glibc2
systems and even then there is a compilation problem with
current gcc which prevented me from playing around with this.
It seems with current gcc you can't access the "%eax" register
from inline assembler anymore. Something like that, tried
it some time ago, forgot the details.
73s HP
--
Hans-Peter Zorn, Karlsruhe, Germany
http://www.stud.uni-karlsruhe.de/~uhsm/ hpz@gmx.net (preferred)
http://1409.org/people/hp/ hp@1409.org (hamradio stuff)
------------------------------
Date: Thu, 28 Sep 2000 10:32:55 GMT
From: magne@radar.no (Magne Mæhre)
Subject: Algorithm for decoding RTTY (Linux project)
In article <8qsvkt$n1o$1@news.rz.uni-karlsruhe.de>, hpz@gmx.net wrote:
>
>If you need some example sourcecode for rtty, amtor and pactor using
>soundcard linux, look at:
>http://www.ife.ee.ethz.ch/~sailer/ham/linux/hf.html
Ah.. right.
I remember looking at that some time ago, but kinda dismissed
it because I thought it required a modified linux kernel
(I usually stick to "stock" kernels due to extreme lazyness :)
I'll look over the code and see if I can learn some of the tricks
of the trade :)
--Magne / la1bfa
------------------------------
Date: 27 Sep 2000 19:59:12 -0400
From: esj@harvee.billerica.ma.us (Eric S. Johansson)
Subject: APRS Operating Question
"Charles Brabham" <n5pvl@swb.net> writes:
> Is this how LandLine Lids such as yourself decide it's "OK" to transmit
> commercial content (and porno, etc) from the Internet over the Ham bands?
man, you are so obsessed with porn. If this is representative of the
old school of packet, then I say, let it die.
--- eric
------------------------------
Date: Wed, 27 Sep 2000 19:45:22 -0500
From: "Charles Brabham" <n5pvl@swb.net>
Subject: APRS Operating Question
To be continued in digest: hd_2000_265B
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