[Moon] WSJT

Leif Asbrink leif at sm5bsz.com
Thu Aug 18 01:12:45 CEST 2016


Hello Petrzilka,

As far as I recall, about 50 years ago, ms skeds were often
two hours. The limitation was that transmissions had to
be continous. If the 2 hour sked the first day was partly
sucessful providing call signs and report but no confirmation,
one would have to start from scratch on the sked the next
day.

For EME the common moon winow should be the time limit.

Have a look at this page:
http://www.sm5bsz.com/kk7ka/kk7ka.htm
"With 50W output power the minimum antenna size is 3.5 
wavelengths (13.7dBd) to achieve the results shown in 
the images below." and "The data rate is limited to about 
1 bit/minute using the most unsophisticated modulation 
schemes. With better frequency stability the threshold 
is probably even lower."

This was in year 2000. I have not been able to find the 
recording so I can not measure the actual S/N. I would guess
that the 350W transmission is in the order of -23 dB in 
a 2.5 kHz bandwidth. It would have been a nice signal for
JT65 but I doubt that JT65 would have been capable of decoding 
a message at 25 W. (probably -35 dB in the JT65 scale)

The bit rate for QRSS would be something like 1 bit per
minute at this S/N. Conventional QRSS with modern frequency 
stability would need a lot of time for a qso a single massage, 
something like IW3NWV DE SM5BSZ is about 140 bits in Morse
code and would take over two hours. The moon window would 
have to be long;-)

Better coding is the obvious solution, but it would be fun if
some modest stations would try the qrss software used on 136
kHz to work EME on 144 MHz at some less extreme timing.

JT65 is supposedly about 13 dB more sensitive than ordinary CW.
That is a factor of 20. That means one would expect it to
take 20 minutes to transfer a message with QRSS at -27 dB or
40 minutes at -30 dB or 2 hours at -35 dB. This is another,
independent way of estimating the perfomance of EME QRSS.

Far more interesting would be a slow QRA64 mode with 10 minutes
for each transmission and a sensitivity that would be about 
a factor of 10 better than the standard mode. Nothing for use 
in a contest, but it could be fun for all the small stations 
around the globe.

73

Leif




> 
> I would have an another question:
> 
> 
> 
> 
> In case that I use some ultra slow mode (like for 136 kHz band) for
> 
> an EME contact with signals below noise, is there any IARU R1 limitation
> 
> or recommendation of maximal QSO duration for a valid contact??? 
> 
> Is 10h long QSO still valid?
> 
> 
> 
> 
> Somebody could be loathing but for an example 70cm MS fsk441 is
> 
> often to set sked for over 1h long.
> 
> 
> 
> 
> 73
> 
> Matej, OK1TEH
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> ---------- Původní zpráva ----------
> Od: tony everhardt <n8wac at yahoo.com>
> Komu: ok1teh Petrzilka <ok1teh at seznam.cz>, Lars Pettersson <sm4ive at telia.com
> >
> Datum: 17. 8. 2016 13:54:59
> Předmět: Re: [Moon] [Moon-Net] WSJT
> 
> "
> 
> 
> My opinion....The contact is in the eyes of the beholder. It doesn't matter 
> what mode that one uses. It's up to the operator to be honest with himself 
> to gather enough information, which should be a full call, even if its 
> pieced together from multiple tx's. For instance.. N8WA what? Again. Last 
> letter. C? 73 Tnx. You or I can't stop the 2 operators from exchanging 
> callsigns via email then claiming it was a good contact. 
> 
> 
> 
> 
> N8WAC
> 
> 
> 
> 
> 
> 
> 
> 
> On Wednesday, August 17, 2016 7:35 AM, ok1teh Petrzilka via Moon <moon@
> moonbounce.info> wrote:
> 
> 
> 
> 
> 
> Check out  http://www.ok2kkw.com/iaru/handbook_7-51.pdf
> (http://www.ok2kkw.com/iaru/handbook_7-51.pdf)
> (http://www.ok2kkw.com/iaru/handbook_7-51.pdf
> (http://www.ok2kkw.com/iaru/handbook_7-51.pdf))
> 
> 7.1 Minimum Requirement for a valid QSO (Vienna 2007) ......................
> ........................................ 89 
> 
> 
> 
> 
> But this is valid just for the IARU Region 1 hi.
> 
> 
> 
> 
> 73
> 
> Matej, OK1TEH
> 
> 
> 
> 
> 
> 
> 
> ---------- Původní zpráva ----------
> Od: Lars Pettersson via Moon <moon at moonbounce.info
> (mailto:moon at moonbounce.info)>
> Komu: Joe Taylor <joe at princeton.edu(mailto:joe at princeton.edu)>, moon@
> moonbounce.info(mailto:moon at moonbounce.info) <moon at moonbounce.
> (mailto:moon at moonbounce.)
> info>
> Datum: 17. 8. 2016 8:53:06
> Předmět: Re: [Moon] [Moon-Net] WSJT
> 
> "It would be interesting to hear your opinion on when a QSO is a QSO?
> The information to be developed?
> On a number of expeditions where Callsigns not existed in Call3txt and 
> where they have been held because of too many characters.
> K1JT even typed here to not use full callsigns and others said not to 
> use the full call: !!!In my eyes, these QSOs are not valid.
> What are your opin?ion Real QSOs or fake.
> Its like sending JT de IVE could be any one so not complete QSO FAKE
> 
> Interesting?
> 
> Lars SM4IVE
> 
> 
> Den 2016-08-17 kl. 00:10, skrev Joe Taylor:
> > Hi Mark,
> >
> > EA8FF wrote:
> >> wow! I agree absolutely with many ,it would be nice to have a system
> >> based on real decodes instead of relying on deep search. To see how
> >> much fakes deep search gives, do the following test: go to say 30 or 20m,
> where
> >> there is plenty of activity and get map65 to work there. Do not transmit 
> and
> >> leave deep search on for some time. you will be receiving reports of 
> people in
> >> your call3.txt, who even do not have 30m or 20m equipment but are in your
> call3.txt
> >> and giving you up to R-reports. Just do the test and you'll be convinced
> >> that any QSO made with deep search on is invalid.
> > Your experiment on 20 or 30 meters shows just one thing: if you choose
> > to turn on deep search (by default it is OFF), you should follow
> > instructions for its use.
> >
> > This decoding option was designed for VHF-and-up use, particularly EME.
> > It is *not* suitable for use at HF, and never has been recommended for
> > such use. If you run the DS decoder on a band full of 20 m or 30 m JT65
> > ignals, many of which are far stronger that EME signals, you're
> > guaranteed to see what appear to be false "decodes". Any careful
> > operator would reject such garbage out of hand.
> >
> > Deep search offers an optional way to get somewhat better sensitivity
> > for very weak JT65 transmissions that contain one's own call or "CQ",
> > followed by a previously decoded callsign and a grid locator or report.
> > This is hardly a revolutionary idea; it's no more than an algorithmic
> > adaptation of the callsign "cheat sheets" (lists of calls known to be
> > active on a given EME band) that have been familiar to EME operators
> > since the 1970s.
> >
> > QSOs that may have benefited from deep search decoding are perfectly
> > valid, and with any normal confirmation they are accepted for DXCC, WAS,
> > and all other awards.
> >
> > -- 73, Joe, K1JT
> > _______________________________________________
> > Moon-Net posting and subscription instructions are at http://www.nlsa.com/
> (http://www.nlsa.com/)
> nets/moon-net-help.html
> >
> >
> 
> -- 
> 
> CW is King!!!!
> 
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