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Subject: HamDigitalDigest 99/313A
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Ham-Digital Digest Sat, 11 Dec 99 Volume 99 : Issue 313
Today's Topics:
AEA PK-88 Help Needed!
German packet radio
RS-232 HELP for internal RTTY modem in DSP-599zx
Used HAM Software?
Wanted To Buy -- All item types --
Send Replies or notes for publication to: <Ham-Digital@UCSD.Edu>
Send subscription requests to: <Ham-Digital-REQUEST@UCSD.Edu>
Problems you can't solve otherwise to brian@ucsd.edu.
Archives of past issues of the Ham-Digital Digest are available
(by FTP only) from ftp.UCSD.Edu in directory "mailarchives/ham-digital".
We trust that readers are intelligent enough to realize that all text
herein consists of personal comments and does not represent the official
policies or positions of any party. Your mileage may vary. So there.
Loop-Detect: Ham-Digital:99/313
----------------------------------------------------------------------
Date: Fri, 10 Dec 1999 00:21:22 GMT
From: rgawtry@timewave.com (Randall R. Gawtry.)
Subject: AEA PK-88 Help Needed!
In article <slrn84vluq.t1s.jrerlewe@techsrv1.tech.mtu.edu>, jrerlewe@mtu.edu
wrote:
>
>Hi everyone,
>I have an AEA PK-88.
>About 4 years ago, it stopped responding. Power was applied and nothing
>would happen but the power light coming on.
>I replaced the Main firmware chip. AEA had sent me an update to the old
>one and I put the old one back in. It worked fine for another 3 years.
>Recently it's stopped responding again, and neither chip works. I'm
>wondering if they are somehow getting damaged by static.
>
>In any case, does anyone know where I can get a replacement firmware for
>the PK-88? New or old, I just want to see it working again-
>THanks,
>Joe
>
>-----------------------------------------------------------------
>Joseph R. Erlewein, N8OUZ -- http://www.qsl.net/n8ouz
> Proud Member HCCA, Hancock Chapter
>-----------------------------------------------------------------
Joe,
Timewave can supply replacement firmware for your PK-88 and other products
manufactured by the the former Advanced Electronics Applications, Inc. of
Lynnwood, WA. We purchased their data products line in April,1997.
Timewave has tech support, repair, upgrades, and accessories for most of the
their data products.
You can contact Timewave in several ways:
www.timewave.com
sales@timewave.com
651-222-4858 (voice)
FAX 651-222-4861
Timewave Technology Inc.
58 E. Plato Blvd.
St. Paul, MN 55107-1827 USA
Give us a call - we'll get you back on the air!
Thank you,
Randy Gawtry, K0CBH
Timewave Technology Inc.
>.
------------------------------
Date: Sat, 11 Dec 1999 01:06:51 -0500
From: Gary Coffman <ke4zv@bellsouth.net>
Subject: German packet radio
On Sun, 28 Nov 1999 23:17:28 +0100, Nico Palermo <nicopal@microtelecom.it>
wrote:
>Gary Coffman wrote:
>
>> There is a 3 dB penalty between MSK and BPSK because the Hamming
>> distance is twice as large for BPSK as for MSK, ie there's only a 90 degree
>> bit to bit phase shift with MSK while BPSK has a 180 degree bit to bit
shift.
>> This gives a bigger decision space for BPSK, and hence the difference in
>> channel performance. That assumes coherent detection. If MSK is decoded
>> incoherently, then the disadvantage for MSK is 6 dB. We agree on that.
>
>Sorry, but there is no penalty between them, nor I'm confusing apples
>with oranges.
>MSK is a CPFSK (continuous phase FSK) signal and it is a modulation with
>MEMORY!
>MSK phase transitions can be represented in a trellis diagram with four
>states (0, 90, 180 and 270 degrees). A Viterbi decoder demodulates them
>optimally, with no penalty over BPSK.
>This happens just because MSK Hamming distance is the same of BPSK when
>modulator's memory is taken into account.
Sorry, that doesn't make any sense. In MSK, a transition is encoded as a
90 degree phase shift. So the decision is "did a 90 degree shift occur or
not?" That's what the demodulator has to decide. There is no coding which
could lead to a decision trellis (unless you supply a baseband coding,
of course, which is a separate issue from demodulation).
With BPSK, the phase shift to be detected is 180 degrees, twice that of
MSK. Assuming linearity in the demodulator, that yields a 3 dB detection
advantage.
To be continued in digest: hd_99_313B
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