From: Rik Strobbe <rik.strobbe@kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Thread-Topic: LF: Re: SlowJT9 v0.9.02: Decode simultaneous
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Date: Tue, 13 Nov 2018 13:38:32 +0000
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Hello Paul, all,

the original slow JT9 submodes make better advantage of the cycle length than the ones currently used in SlowJT9.
Eg.: where the current JT9-5 version has a transmission duration of 245 s, the original JT9-5 had a transmission duration of 292 s (both for a 300 s = 5 min cycle).
And longer transmission duration = longer symbol length = better SNR.
The theoretical advantage of the original submodes over the currenty used ones is 0.46 dB for JT9-2 and 0.74 dB for JT9-5. 

73, Rik  ON7YD - OR7T

________________________________________
Van: owner-rsgb_lf_group@blacksheep.org <owner-rsgb_lf_group@blacksheep.org> namens N1BUG <paul@n1bug.com>
Verzonden: dinsdag 13 november 2018 12:42
Aan: rsgb_lf_group@blacksheep.org; 600MRG@mailman.qth.net
Onderwerp: Re: LF: Re: SlowJT9 v0.9.02: Decode simultaneous

Hi Rik, all,

I am still thinking about this. :)

I can see some advantages both ways.

If we assume that there will be significant non-scheduled activity
(people calling CQ using more than one of the JT9 submodes), then
being able to decode all three simultaneously would be an advantage.
We can watch the band for all activity and work people on any of the
three modes.

However so far my experience has been that on 2200m QSOs only happen
by prearranged schedule, not by CQ. Most of the 630m trans-Atlantic
QSOs were the result of activity coordinated via these email lists.
If this is the pattern of activity we can expect, maybe it becomes a
bit less important having the ability to decode all modes at the
same time? In cases where we are coordinating the activity in
advance, we can also choose the mode in advance.

The original JT9-2 and -5 specification has some advantages. One is
that it could preserve compatibility with other software and
devices. There could be some valid reasons for wanting to be able to
transmit with the popular U3S and receive with SlowJT9. One would be
as I proposed the other day, beaconing on alternating modes to
collect evidence on the relative success rates. Another would be as
2E0ILY and myself did last year, beaconing just one JT9 mode to see
if it offered QSO capability between particular stations.

Doesn't fully utilizing the time slot also suggest the possibility
for being able to decode at a s lightly lower level? Maybe it's not
enough to worry about, but at JT9-5 the difference in time utilized
is substantial.

There may be some (lucky ones who are able to make it work) who want
to continue using the old JT software which had these submodes in it.

I am not urging you to do anything. I am just offering some thoughts
about the choices.

73,
Paul N1BUG


On 11/13/18 3:17 AM, Rik Strobbe wrote:
> Hello Jim, all,
>
>
> my plan was that SlowJT9 will decode all JT9 submodes and show
> them on the same decoder window. The user can see for each
> decoding what the submode is (the M parameter in the decoder
> window will show 1, 2 or 5). If the user double-clicks on any
> call, SlowJT9 will change the TX submode to that of the received
> station (you double-clicked on) and you are ready for a QSO.
>
> No hastle with 2 or 3 instances ...
>
> But, as said before, this might be difficult with the initial
> JT9-2 and JT9-5 transmission durations (49 sec for JT9-1, 109 sec
> for JT9-2 and 290 sec for JT9-5) decoding for all submodes will
> happen at (almost) the same moment. On a moderate PC during the a
> single JT9 decoding the CPU usage peaks to 40-50%. What will
> happen if 3 instances of the JT9 decoder are invoced at the same
> time?
>
> An alternative would be to decode the 3 submodes one by one (in
> series). But I noticed that on a busy band one JT9 decoding can
> take several seconds, so 3 decodings can take so much time that
> it exceeds the 10 seconds "response time" (between the end of
> transmission an start of the next cycle), preventing the user
> from responding in time.
>
>
> With the current JT9-2 and JT9-5 transmission times in SlowJT9
> (49 sec for JT9-1, 98 sec for JT9-2 and 245 sec for JT9-5) there
> is alway at least 10 seconds difference between any (JT9-1, JT9-2
> or JT9-5) decoding, what should be no problem unless a very slow
> PC is used.
>
>
> So at this moment I am seeking advice about how to proceed. My
> aim to to create a tool that is useful for DX communication on
> 472kHz and 136kHz, so "your wish is my command" (but keep it
> realistic).
>
>
> 73, Rik  ON7YD - OR7T
>
>
> ________________________________ Van:
> owner-rsgb_lf_group@blacksheep.org
> <owner-rsgb_lf_group@blacksheep.org> namens James Hollander
> <mrsocion@aol.com> Verzonden: maandag 12 november 2018 23:40 Aan:
> rsgb_lf_group@blacksheep.org; 600MRG@mailman.qth.net Onderwerp:
> LF: SlowJT9 v0.9.02: Decode simultaneous
>
> Rik, all,        So, as I understand it, on some ordinary night a
> MF station would/could run at least two software instances of
> JT9—one instance set to decode 2 minute slow JT9, and the other
> instance decoding 1 minute JT9 concurrently.
>
> The 1st  s/w instance is set for slow JT9.   If the station you
> want to call or have respond to a CQ is low-SNR like a QRP,
> transcontinental, or transoceanic station, then you activate your
> transmission using the slow JT9 software instance.   If low-SNR
> stations comprise the only intended reception, then slow JT9 is
> all you use and forget the 2nd s/w instance.   You get deep-SNR
> receptions and QSOs that regular JT9 can’t deliver.
>
> The 2nd s/w instance is set for regular JT9. Suppose the station
> you want to call or have respond to a CQ is likely above, say,
> the 50% decode probability, at least SNR -27 dB most of the time.
> Then you activate your transmission on-the-fly instead with
> regular JT9 using that 2nd s/w instance.  That way, you either
> get a reply after 1 minute or have the chance to repeat your
> transmission.
>
> The nimble operator uses the 1st  or 2nd  s/w instance that’s
> simultaneously running as conditions and as sought-after stations
> warrant.  No need to change TX frequency.  The DX may be on some
> other frequency than you, but that’s fine.  You call them with
> slow JT9 or regular JT9 as you decide on-the-fly without changing
> your frequency and they will see you on their PC display if they
> can.
>
> Other stations may be running either slow JT9 or regular JT9 at
> any given time, and that’s fine too because you can receive them
> either way.  You’ll see stations TXing slow JT9 on one decoder
> window and stations TXing regular JT9 on the other decoder
> window. If a station sends slow JT9 for a while and then regular
> JT9 for a while, you’ll see that station go from one decoder
> window to the other.
>
> If a station is already running regular JT9 diversity with two RX
> antennas and two regular JT9 decoders connected to SDR sub-RXs,
> you just add two more decoders for slow JT9 diversity as well.
> Depending on your PC, use a PC powerful enough to run the s/w
> instances concurrently.
>
> Feel free to clarify if I’m missing anything important.  Very
> interesting!  73, Jim H  W5EST
>
>
> -----Original Message----- From: Rik Strobbe
> <rik.strobbe@kuleuven.be> To: rsgb_lf_group
> <rsgb_lf_group@blacksheep.org>; rsgb_lf_group
> <rsgb_lf_group@yahoogroups.co.uk> Sent: Mon, Nov 12, 2018 4:05
> pm Subject: Re: LF: SlowJT9 v0.9.02
>
> Hi Paul, it seems that we will have to make a choice: - either
> the old JT9-2 and JT9-5 standard and only decoding one mode at a
> time - or keeping the current JT9-2 and JT9-5 parameters and keep
> the option open to decode all JT9 submodes simultanious. I tend
> to go for the second option, but everyone is welcome to convince
> me otherwise. 73, Rik ON7YD - OR7T