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Ham-Digital Digest Fri, 3 Dec 99 Volume 99 : Issue 310
Today's Topics:
German packet radio
Kenwood TH-D7A 24hr review (2 msgs)
Kenwood TS-570D and Kam
RS-232 HELP for internal RTTY modem in DSP-599zx (5 msgs)
Software updates on the web
Used HAM Software?
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We trust that readers are intelligent enough to realize that all text
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policies or positions of any party. Your mileage may vary. So there.
Loop-Detect: Ham-Digital:99/310
----------------------------------------------------------------------
Date: Sun, 28 Nov 1999 23:17:28 +0100
From: Nico Palermo <nicopal@microtelecom.it>
Subject: German packet radio
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.
A memoryless coherent detector is not optimal for CPFSK signals. Here is
another intuitive demonstration:
MSK is just a variation of the OQPSK modulation: OQPSK uses rectangular
pulses, MSK uses sin(t) pulses instead. As in OQPSK the optimum MSK
demodulator is the matched filter and the integration time spans the
duration of one symbol in each quadrature channel, which is two times
that of a memoryless coherent FSK receiver, giving 3 dB improvement over
the memoryless detector.
Even from this point of view MSK Hamming distance is the same of OQPSK,
which is the same of QPSK, which is the same of BPSK.
> MSK does *not* have a constant amplitude envelope. It does not pass through
> zero when the vector goes from bit to bit as BPSK does, but there is a 3 dB
> variation as the vector moves from bit to bit. (This is the chord to arc
amplitude
> difference as the vector rotates 90 degrees.) If you amplify it with a Class
C amp,
> the spectrum will balloon to a larger value than if you use a linear amp.
It looks like you are speaking of OQPSK rather than MSK.
Unfiltered MSK has constant envelope.
Baseband filtered MSK variations, i.e. GMSK, have constant envelope and
very low amplitude sidelobes, unaffected by Class C amps.
Nico Palermo, IV3NWV
>.
------------------------------
Date: Thu, 2 Dec 1999 21:59:17 -0800
From: "Walter Dunckel" <walterd@radiohound.com>
Subject: Kenwood TH-D7A 24hr review
You are right! 24 hours isn't much time to get to know a radio! Since I
wrote this review, about a year has passed, and I have gotten to know a lot
about the radio. In fact, I liked it so much that I created a web site based
on this radio. You can check it out at http://www.radiohound.com . In fact,
there is even a "real" review of the TH-D7 on my page, by Alan Crosswell.
As far as battery life, it is based on many things. Particularly how time
the radios squelch is on, and how much time you tx, if you are in dual band
mode, and if you have your TNC/APRS turned on. However, I am happy with the
battery capacity. In fact, the stock battery can be replaced with an equal
sized maha that packs 1050mAh with their 9.6 volt battery compared to the
stock 600mAh.
Call me old fashioned, but I am running the LATEST version of terminal.exe.
Why? Is there something else out there? Just kidding ...... sort of. I do
use this with my Windows CE device also, nothing fancy, but functional.
And the best unexpected bonus:
You can control any function of the radio through the serial port using not
so proprietary commands. Check out http://www.radiohound.com/d7zpinfo.htm
for more info on this.
As for price.........
You have to think about what you are getting:
Dual band radio - $300, (almost) fully functional 9600/1200baud TNC - $100,
integrated APRS program built in - $50, all this integrated into a handheld
................ PRICELESS....... or about $450. You decide.
The TH-D7 is packed with functions, and does take a little more time to
master than most radios. In many ways I am still learning. Another great
resource is http://www.tapr.org . Check out their APRSHT SIG (special
interest group) for a ton of information.
Enjoy,
Walter
O'Neal <oneal@pacbell.net> wrote in message
news:367c9eb8.7550645@news.pacbell.net...
> On Tue, 15 Dec 1998 16:29:07 -0800, Walter Dunckel <wdunckel@best.com>
> wrote:
>
> >
> >Saw the TH-D7A, and had to have one. Here are a few things I have
> >noticed since I purchased it 24 hours ago.
>
> >5. Although not very close to the size of a brick, it is similar in
> > shape. I like the shape of my ol TH-28 a lot better, but then I
> > don't have a 9.6volt battery in it!
> >
> >If any of you have any questions about the radio, I will attempt to
> >answer them.
> OK
>
> How much did this beast set you back ?
>
> 24 hours is not much operating time, but do you have a feel for how
> the battery life is ? With a full charge can you work for a couple of
> hours or more less ?
>
> What terminal program you running with the TNC ?
>
> Steve
> N6CRR
>
>.
------------------------------
Date: Fri, 3 Dec 1999 00:38:32 -0600
From: "Rick Ruhl" <ricker@cssincorp.com>
Subject: Kenwood TH-D7A 24hr review
Walter,
PakRatt CE will work with the TH-D7A and give you split screen operation..
and it's FREE.
http://www.cssincorp.com/pakrattce
--
Rick Ruhl
President, Creative Services Software
http://www.cssincorp.com
Walter Dunckel wrote in message <827m00$o84$1@nntp4.atl.mindspring.net>...
>You are right! 24 hours isn't much time to get to know a radio! Since I
>wrote this review, about a year has passed, and I have gotten to know a lot
>about the radio. In fact, I liked it so much that I created a web site
To be continued in digest: hd_99_310B
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