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
* Contestia derived from Olivia.
* Contestia 250/4 is channelfree like psk or rtty. BW less than
rtty and same as psk125, 39wpm, snr -9dB.
* 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.
* 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.
* Concept testing period to the end of year 2010. Everybody is
welcome.
More info contestia.blogspot.com <http://contestia.blogspot.com/>
--
vy73, Jaak
es1hj
--
Kirjutas ja tervitab
Jaak Hohensee
