Hello Skip,
About Contestia:
I think this mode is a better compromise between robustness and speed than
Olivia (too much robustness) and RTTYM (very fast but with the problem of
having two sets of characters as in RTTY, i.e letters and figures, and hence
much risk of packet of errors).
>but it would be helpful if Patrick would assign Reed Solomon Identifiers to
>include those variants.
RR for all, but I have not seen demands to our RS ID group...
73
Patrick
----- Original Message -----
From: KH6TY
To: digitalradio@yahoogroups.com
Sent: Monday, May 10, 2010 1:24 PM
Subject: Re: [digitalradio] Contestia 250 - new concept for usage
Jaak,
I agree with your reasoning in testing Contestia 250/4. I also think that a
good approach would be for EVERYONE to use RSID so a station can shift the QSO
mode according to typing preference or propagation conditions, as determined at
either end of the QSO. Multipsk, DM780, and Fldigi already support both
Contestia 250/4 and Contestia 250/8, so it will be easy to compare modes to see
which one arises as the preferred one. Basically, Olivia has now become favored
by many over MFSK16 because it is easier to tune, and works well into the
noise. I suspect that the same will happen with Contestia, but it will be
always more comfortably fast than Olivia under the same conditions, of course.
Thanks again for the PathSim tests on the wider Contestia modes. That has
been very helpful in deciding which is the best overall compromise between
speed and lowest S/N on our UHF paths. On UHF, we have prepared macros in
Fldigi to quickly switch between Contestia 1000/64 and Conterstia 2000/64, but
it would be helpful if Patrick would assign Reed Solomon Identifiers to include
those variants. Because there is much more space available on UHF, we can use
the wider modes to withstand Doppler shift and spreading, whereas we find
anything more narrow than 500 Hz simply does not survive.
It is good to have choices!
73, Skip KH6TY
Jaak Hohensee wrote:
Skip, I agree with you.
My considerations to prefer in HF Contestia 250/4 format is related to the
idea to find some compromise for bpsk31 folk, Olivia light users, and rtty folk
when the propagation is not enough good for bpsk31 and rtty.
So Cnt 250/4 with 39wpm is the first alternative for bpsk and rtty folk and
the last alternative for Olivia hardusers ;)
The idea to use 250/4 format motivated also by fact that Cnt 250/4 signals
are seen in wtrfl until the copy lost (-9dB). 250/8 is washed out from wtrfl
around -10dB. Both, psk31 and rtty users was wont to see signals on wtrfl. To
see signals is motivated also from QRM reducing viewpoint.
The idea to make 2-step default switch from 250/4(-9dB) to 250/16 (-15dB)
and so get additional snr -6dB is compensate 250/8 format snr-advantage.
Default shift need default procedure what/how to do when the copy is lost.
WPM considerations
29wpm (250/8) is good speed from cw-viewpoint, but too less from rtty/psk31
viewpoint. 39wpm (250/4) is somekind compromise between the different speed/snr
expectations.
vy73, Jaak
es1hj
10.05.2010 2:59, KH6TY kirjutas:
Hi Jaak,
Great idea to start a long test of Contestia 250/4!
Perhaps Contestia 250/8 can also be compared in actual practice to
Contestia 250/4. Contestia 250/8 is slower (at 29 wpm), but decodes 2 dB deeper
into the noise, which may be important when there is QSB (fading) and the
signal is already near the noise level ( such as when the band is going out).
Although I can type over 50 wpm, my personal feeling is that 29 wpm is fast
enough for a QSO, but Contestia at 78 wpm (3 dB less sensitive) is more
reasonable for passing traffic (if conditions can support 3 dB less
sensitivity). If not, then to be able to pass the traffic at all, it has to be
sent at a slower, more sensitive speed, such as Contestia 250/4.
It all depends upon the average individual preference for typing speed
for QSO's vs conditions.This may become clear during your tests. I hope the
testers will make their minimum typing speed preferences known, as well as how
well the mode works.
73, Skip KH6TY
Jaak Hohensee wrote:
Hi everybody
a.. Contestia derived from Olivia.
b.. Contestia 250/4 is channelfree like psk or rtty. BW less than
rtty and same as psk125, 39wpm, snr -9dB.
c.. So Contestia 250/4 is good narrowband alternative for psk31 or
rtty folk, specially when propagtion is not for psk/rtty or signals are too
weak.
d.. Contestia 250/4 is good mode for mid- or high-latitude folk. Many
times there are disturbed propagation path not suited for psk or rtty.
e.. Concept testing period to the end of year 2010. Everybody is
welcome.
More info contestia.blogspot.com
--
vy73, Jaak
es1hj
--
Kirjutas ja tervitab
Jaak Hohensee
