Jose,
Just as you were posting this message I was stumbling on a web site that
agreed with your comment.
With further searching I think I have the relationship. The QEX article has
the statement that to go from the 3kHz bandwidth used you "subtract 34 dB
and add 10 log of the desired bandwidth in
Rud,
You can see the variations in the ionosphere as a phase modulator
embedded in the channel. So, it will phase modulate whatever you attempt
to get thru it. Actually, it has a phase modulator embedded for each
arriving path.
With differential encoding, and signalling speed higher than the
All,
For what it's worth, I ran several digital modes through a high-latitude
ionospheric path simulator and recorded the results. The signal spread
was set to 30Hz and path delay was 7 milliseconds. With these settings,
the audio sounds much llike the most extreme polar path distortion and
th
Rick wrote:
> Something that has long been unclear to me is how can we have all these
> modes that work far below zero db S/N and yet the Eb/No (energy per bit
> relative to noise) can theoretically not go much lower than between 1
> and 2 dB below zero dB according to the Shannon Limit?
That
I thought about the same. On pactor, the doppler perturbation is 31/100
of the signalling rate, thus, results less affected, even without taking
into account the FEC and QRQ strenghts that Pactor also packs along.
73,
Jose, CO2JA
Vojtech Bubnik wrote:
>> PSK31 failed, bad copy even under goo
Rick,
Good questions.
My only response right now is "I dunno".
Back to the books.
The QEX article based its results on a rate of 2% character error rate.
PSK-31 with AWGN needed -11 dB. Crunching the numbers that at -10 dB you
need a bandwidth of 227 Hz for 31.25 bps. At -11 dB would need some
How wide is 45 baud RTTY ?
At 07:52 PM 10/26/2007, Rick, KV9U wrote in part:
>How do you make a wider bandwidth for a given mode? Isn't the bandwidth
>based on the baud rate to begin with?
My understanding is that the Eb/No is more of what you would find at the
antenna terminals, without the bandwidth of the receiver?
Using your data on your web site, how does this relate to say, PSK31
modulation? Would the SNR also be at zero with the 31 bps baud rate with
the B/C (Bandwidth in
Would the phase distortion that can corrupt a PSK signal occur the same on a
M-PSK signal?
If the phase distortion affects all the sub channels then doing differential
PSK among the sub channels would work where symbol to symbol DxPSK would not
work.
Rud Merriam K5RUD
ARES AEC Montgomery Count
Hello to all,
For the ones interested by doing ALE and ARQ FAE in small bandwith (400 Hz), I
have derived from the standard ALE a new ALE which bandwidth is 400 Hz (instead
of 2000 Hz) and which name is "ALE400".
This ALE system has exactly the same functions as the standard ALE (in
Multipsk)
> I just read the Pactor 3 specification. I am not sure that it is
OFDM. It is
> multi-tone but the spacing of the tones seems wider than OFDM
requires.
The spacing is derived from the "integration time" only, while the
baudrate is the sum of "integration time" plus "guard interval".
(integre
Vojtech,
Good points.
After some further reflection on the article I am not sure many conclusions
can be made from the material beyond its specific results about the modes
covered. The various modes are to dissimilar in all aspects to draw any
conclusions on whether PSK is better than MFSK, for
I just read the Pactor 3 specification. I am not sure that it is OFDM. It is
multi-tone but the spacing of the tones seems wider than OFDM requires.
But I may be missing something in the technical definition OFDM of that
differentiates it from MT.
Rud Merriam K5RUD
ARES AEC Montgomery County,
Rick,
The measurement of SNR and Eb/No are two different measurements. The
confusion comes because they are both cited in dB. It took me quite a lot of
rereading material to clearly understand them. I dumped my understanding of
it onto my web site at
http://thehamnetwork.net/wiki/#Shannon-Hartley%
Hello Rick,
S/N in dB is measured versus a conventional noise bandwidth (3 KHz in general).
This permits to compare modes against gaussia noise as you consider the signal
power (indifferently of the way you modulate and the coding you use) and the
noise power (the same for all modes).
Eb/N0 is
Hello Rob,
To measure the IMD you can transmit PSK31 or better PSK63 or 125 idling. An Ham
close to you QRA will be able to give you an indication of your IMD
(approximative but sufficient).
Here an extract of the Multipsk help about IMD (you can do this measure with
all PSK31 softs).
73
Patr
Hello Vojteck,
>I think Patrick has a similar mode in MultiPSK, which limits further
>the character table, making the mode work with even lower S/N.
You are right, I have tried PSK10 and PSKAM10. The big problem with these low
speeds is the ionospheric Doppler modulation. Without any Doppler in
Something that has long been unclear to me is how can we have all these
modes that work far below zero db S/N and yet the Eb/No (energy per bit
relative to noise) can theoretically not go much lower than between 1
and 2 dB below zero dB according to the Shannon Limit?
Then you need to take the
--- In digitalradio@yahoogroups.com, Rick <[EMAIL PROTECTED]> wrote:
>
> I think that I have mentioned some of this before, but unless you
have a
> club of some kind where interested hams join and "buy in" to a concept,
> a numbering system may not be something that many will gravitate toward.
I
Rob,
If you can get someone to send you a screenshot of what your signal
looks like, it will go a long way towards solving your problems and
won't cost anything.
It will help tell whether your problem is overmodulation or RF
feedback.
Overmodulatio looks like many copies (sidebands) of the si
Hi Rob,
I've found this very helpful:
http://www.usinterface.com/IMDMeter.html
Good luck and look for you on the bands.
73,
Tony, AD1Y
--- In digitalradio@yahoogroups.com, "charmquark69" <[EMAIL PROTECTED]>
wrote:
>
> Hi all,
>
> just joined the group and have been using digital modes (=P
On Fri, 26 Oct 2007 08:03:10 -, charmquark69 wrote:
> ALC set really low
It's better to have no sign of ALC. If the Circuit must work, the Input is to
High and the Audio could be dissorted. I
use a Kenwood TS-480. My Setup of the RIG and the Audio is as follow:
HF-Power Output is on Maxim
Hi, Rob;
You might want to consider this - http://www.usinterface.com/IMDMeter.html
I'm planning on buying one.
Good luck,
Mike N5UKZ
charmquark69 wrote:
>
> Hi all,
>
> just joined the group and have been using digital modes (=PSK only)
> for a couple of weeks now.
>
> I've occasionally got a
Now Walt be fair, It does more then just P3.
Besides, remember what the first digital watches came
out. I the for around 150 bucks or more. You can now
get the same watches for $5 or less.
You think maybe some of them big bucks could
be going for R&D ?
At 09:37 PM 10/25/2007, you wrote:
>If I in
Hi all,
just joined the group and have been using digital modes (=PSK only)
for a couple of weeks now.
I've occasionally got a "bad modulation" report - two or three times
out of maybe fifty contacts - and was wondering how I could
personally check the modulation as the signal is transmitted
--- In digitalradio@yahoogroups.com, "John Becker, WØJAB" <[EMAIL PROTECTED]>
wrote:
>
> not a thing here in the midwest of the US.
>
Hi John
You missed it as it switched of on the 24th but since then I
have heard something on the same frequency using different modes.
I'm not sure if it's been he
--- In digitalradio@yahoogroups.com, Walt DuBose <[EMAIL PROTECTED]> wrote:
>
> Rud Merriam wrote:
> > After a comment off list from Demeter I checked the Pactor
specifications.
> > It uses DBPSK or DQPSK.
> >
> > Why do the reports about Pactor indicate it is more robust than
the QEX
> > article
Andy, are you aware that RSS access to the group has been deleted? RSS
is a great way to keep your inbox from getting jammed.
--- In digitalradio@yahoogroups.com, "w1mnk" <[EMAIL PROTECTED]> wrote:
>
> What happened to the RSS feed. It stopped working on 10/22, and the
> link is gone from the home
> PSK31 failed, bad copy even under good SNR, with 3 ms multipath and
10 Hz
> Doppler. It did not do well with 2 ms multipath and 1 Hz Doppler.
>
> Since Pactor uses PSK I wondered if it would similarly fail as shown
by the
> PSK31 results. I suspect that it handles Doppler better through
frequenc
> Why do the reports about Pactor indicate it is more robust than the QEX
> article would indicate?
I did not read the QEX article, but I hope I learned something about
PSK modulation with regard to ionospheric flutter over the years I am
developing PocketDigi.
1) PSK is very efficient in white
Is there a way of getting the article for the group. It is very important.
Thanks
Omar YK1AO (now operating under 6C60O commemorating 60 years amateur radio in
YK-land)
- Original Message -
From: Rud Merriam
To: digitalradio@yahoogroups.com
Sent: Thursday, October 25, 2007 8
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