Hello Phil,
Ionospheric Doppler produces fluctuations in the phase of the BPSK
transmission. In Multipsk for BPSK, there is an indicator which name is
"Quality" (for 1 to 5). It can give an idea of the Doppler: if the signal is
strong and the quality is bad, it means that there is some Doppler. The worst
case and I see this once, transmission is not possible in BPSK (or only at very
high speeds as 125 bauds or more).
Signal Quality (Q)
A BPSK signal generates 2 phases: 0 and 180 °. More the signal is pure, the
more the decoded phase is close to one of these two preceding phases. The
average distance to these phases is computed then filtered over 2 seconds.
According to the obtained distance, it is given a note between 1 to 5:
a.. distance>30 °: Q=1 (very bad),
b.. distance between 16 and 30 °:Q=2 (bad),
c.. distance between 8 and 16 °: Q=3 (medium),
d.. distance between 4 and 8 °: Q=4 (good),
e.. distance <4 °: Q=5 (very good).
Note: a random signal has an average distance of 45 °.
73
Patrick
----- Original Message -----
From: Phil Williams
To: digitalradio@yahoogroups.com
Sent: Tuesday, January 05, 2010 2:49 PM
Subject: Re: [digitalradio] IZ8BLY's PSK63F
Demonstrating a suite of digital coding methods are vulnerable to Doppler
spread does not tell the whole story. What does the signal look like on the a
spectrogram when subjected to Doppler spread? Yes, you have incomplete or
scrambled text, but then the root cause of that could be anything.
It would be valuable to the community to be able to recognize the presence of
Doppler spread by some visual or aural means. Armed with this information then
one begins to make choices of other modes that would be less vulnerable to the
effects of Doppler spread.
philw de ka1gmn
On Tue, Jan 5, 2010 at 2:13 AM, Tony <d...@optonline.net> wrote:
Phil,
> What about PSKFEC31 under the same test scenarios?
Have a look:
Path Simulation: High Latitude (Moderate)
Path Delay: 3ms, Doppler spread 10Hz
Pangram Text: Quick Brown Fox
PSK31FEC
t e tio E ttaeH loo etee- e e e ˆyaooe n o
ao t aeepvede n neete ueeeu .tna0 o een
it=pctidr a ieae t e tio E ttaeH loo etee- e e
etˆyaooe on oe ne 6etnuEenoel o·b geogtee
PSK63F
the quick brown fox jumps over the lazy dog
the quick brown fox jumps over the lazy dog
the quick brown fox jumps over the lazy dog
Tony -K2MO
----- Original Message -----
From: Phil Williams
To: digitalradio@yahoogroups.com
Sent: Monday, January 04, 2010 5:16 AM
Subject: Re: [digitalradio] IZ8BLY's PSK63F
Very interesting. What about PSKFEC31 under the same test scenarios?
Certainly, there would be more a in throughput, but that is a matter of some
liberal use of CW shorthand.
philw de ka1gmn
On Mon, Jan 4, 2010 at 2:48 AM, Tony <d...@optonline.net> wrote:
All,
Recent path simulation tests indicate that Nino Porcino's PSK63F offers
better performance over PSK31 and PSK63 in a couple of areas. The most
significant improvement is it's ability to endure Doppler spread found on
paths that cross the polar ionosphere. Both PSK31 and PSK63 fail miserably
in this area; see high-lat test samples below.
Path Simulation: High Latitude (Moderate) Path Delay: 3ms, Doppler spread
10Hz
Pangram Text: Quick Brown Fox
PSK63F -- the quick brown fox jumps over the lazy dog
PSK63 -- mev roe tt#dtorl|f- bn ô mp e o ihe Fzy dg
PSK31 -- nls oSer Òe naAeta qlipM h nV o T rn agâ o
RTTY -- TH QACKH492, FOJUMP OR THTLAZY G
Sensitivity-wise, it's quite a bit more sensitivity than PSK63, but only
marginally better than PSK31. Although it's speed is about 25% faster than
PSK31, it's about 40% slower than PSK63. Average wmp rate seems to be 63
wpm
for PSK63F.
Lowest S/N (sensitivity)
PSK63F -12db
PSK63 -7db
PSK31 -11db
RTTY -5db
Additional path tests indicate that PSK31 and PSK63F perform about the same
under moderate mid-latitude conditions (CCIR fading channel). Tests show
that PSK31 and PSK63F will outperform PSK63 when signals are weak under
quiet conditions since they both have greater sensitivity.
It would be interesting to hear from our HF digital friends up north who
experience the distorting effects of the polar ionosphere on a regular
basis; this is where the PSK63F mode can be put to the test.
Available software:
Nino Porcino's Stream -- http://xoomer.virgilio.it/aporcino/
Patrick Lindeckers Multipsk -- http://f6cte.free.fr/index_anglais.htm
(thanks for including PSK63F Patrick)
Tony, K2MO
