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PA2AGA > HDDIG 04.07.00 00:02l 186 Lines 6727 Bytes #-9412 (0) @ EU
BID : HD_2000_178G
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Subj: HamDigitalDigest 2000/178G
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From: PA2AGA@PI8HGL.#ZH1.NLD.EU
To : HDDIG@EU
Date: Mon, 03 Jul 00 19:08:00 MET
Message-Id: <hd_2000_178G>
From: pa2aga@pe1mvx.ampr.org
To: hd_broadcast@pa2aga.ampr.org
X-BBS-Msg-Type: B
So Peter, when you say "CW" do you mean Morse code or OOK? One is
an alphabet (like Varicode is) and one is a modulation (like BPSK
and FSK are). Or do you mean the combination?
I don't see any advantage in OOK. The alphabet is fine, but
really independent of the modulation as far as I can see. It's just
Huffman enccoded and not something to get too excited about
I would've thought.
> Always was digital, always will be digital.
You can use a computer to sample it and decode it, but that doesn't
make it digital. You can use a computer to recognise speech and
music these days too.
> Gary, if you cannot make intelligent contributions to this thread, I suggest
> that you go back to the "rec.radio.amateur.antennas" NG, you know more about
> antennas than you do digital communications!
And that was just plain rude..
Hamish
--
Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>
------------------------------
Date: Sun, 02 Jul 2000 16:31:06 -0400
From: Gary Coffman <ke4zv@bellsouth.net>
Subject: how does PSK31 really work?
On 1 Jul 2000 02:06:31 GMT, Charles T. Young <ctyoung@mtu.edu> wrote:
>I would like to know a couple of things:
>
>How does PSK31 really work?
Very well. :-)
>Is it an ascii character set?
No, it uses Varicode, which is a variable length
character encoding which offers some compression
on plain text. This allows use of 31 baud to convey
about 55 WPM.
>How
>is the modulation accomplished?
At audio. It is a binary phase shift keying (BPSK) method,
done at baseband and fed to a SSB capable radio.
(There's also a QPSK variant done basically the same way,
but because the phase shifts are 90 degrees instead of 180
degrees, it matters whether your radio operates USB or LSB.
You have to match the sense the other station is using. For
ordinary BPSK it doesn't matter which sideband you use.)
>I have heard that DSP functions are present in a sound card.
>Can someone tell me some more about that? Besides knowing how it
>is used in PSK 31, I have another job for it. I want to do signal
>averaging in the time domain. Another thing I would like to be able
>to do is synchronous detection.
Some sound cards have limited DSP functions built in, but most
programs do not use them (because the brand of sound card would
then matter). The sound card is used only as an analog to digital
converter and digital to analog converter (typically by calls to the
Windows sound API, or the corresponding Linux sound API). All
signal processing is done by the main CPU of the computer,
hence the usual requirement of a Pentium (or better) class
computer to handle the processing. Since those are the norm
today, that's no handicap.
There are basically two ways to do I/Q demodulation. The direct
method feeds I to one channel (say the left channel) and Q to the
other (with I and Q being generated by an external LO and quadrature
mixers, ie as in the R2 receiver). I haven't had much success with
this method on a PC, though it works fine with dedicated DSP
hardware. I think it is because of the interrupt timing, and OS
dependencies, the PC has, but it could be just my ineptness at
programming this sort of thing.
The second method digitizes the composite signal as if it
were just a low IF conversion, then uses numerically simulated
oscillators and delays to do the entire demodulation process
in software. This is more complex, both on the radio side and
the software side, and has some practical drawbacks, but it
works on the PC under the usual operating systems.
Once you have I and Q, synchronous detection is a piece
of cake.
Gary
Gary Coffman KE4ZV | You make it |mail to ke4zv@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
------------------------------
Date: 2 Jul 2000 22:00:05 GMT
From: jeffreyh@Hawaii.Edu (Jeffrey Herman)
Subject: List of the rec.radio newsgroups
Archive-name: radio/personal-brief-introduction
In an effort help ensure a poster's article reaches the appropriate
audience, below is a list of the rec.radio newsgroups. In most cases,
a group's name will explain its purpose. Cross-posting should rarely
be necessary.
rec.radio.broadcasting (devoted to the broadcast industry; moderated)
rec.radio.cb
rec.radio.info (periodic informational bulletins; moderated)
rec.radio.scanner
rec.radio.shortwave
rec.radio.swap (for buying, selling, and trading; not a discussion group)
rec.radio.amateur.antenna
rec.radio.amateur.boatanchors (tube-type communications equipment)
rec.radio.amateur.digital.misc (packet, pactor and other digital modes)
rec.radio.amateur.dx (long-distance amateur communications)
rec.radio.amateur.equipment (questions, comments regarding commercially-
built amateur gear; not for buying/selling)
rec.radio.amateur.homebrew (devoted to home-building ham gear)
rec.radio.amateur.policy (issues include code, restructuring, local
restrictions in conflict with FCC R&R)
rec.radio.amateur.space (satellites, meteor scatter, EME)
rec.radio.amateur.misc (any amateur topic not covered in the above groups)
(At least two other English language radio hierarchies exist, prefixed
with "uk" (United Kingdom), and "aus" (Australia), in place of "rec.")
Again, cross-posting should rarely be necessary. Many times, a long-
running thread results from a single cross-posted article, and its
content drifts further and further away from being "on-topic" in the
various NGs which receive each and every followup.
For more detailed information, see "Guide to the Rec.radio Newsgroups"
posted on the 15th of each month.
Jeffrey Herman, KH6O
------------------------------
Date: Sun, 2 Jul 2000 16:41:13 -0500
From: "Randy Thomson" <rthomson@delete.imagin.net>
Subject: TM-D700A and Tripmate?
Is anyone using the Trimpmate as a GPS with the Kenwood TM-D700A?
I tried today without any success. I terminated the Kenwood GPS cable with a
DB-9 male connector with Pins 2&3 jumpered to loop the ASTRA signal back,
then connected the red wire to pins 2-3 and the shield to pin 5. Set the
D700 to NMEA GPS mode. No joy. didn't get any POS input on the display, and
no Auto APRS output.
Need some help, or a reason I have to go get a GPS III+.
Thanks,
Randy - K5MW
------------------------------
End of Ham-Digital Digest V2000 #178
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