From: Rik Strobbe <rik.strobbe@kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>,
        "600MRG@mailman.qth.net" <600MRG@mailman.qth.net>,
        "rsgb-lf-group@groups.io"
	<rsgb-lf-group@groups.io>
Thread-Topic: SlowJT9 update (v0.9.15.0)
Thread-Index: AQHUuW6GReIGNCCA4UORsMuWFMRWMw==
Date: Thu, 31 Jan 2019 14:43:04 +0000
Message-ID: <1548945782023.57164@kuleuven.be>
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Subject: LF: SlowJT9 update (v0.9.15.0)
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Dear all,

Beta-release v0.9.15.0 of SlowJT9 has been uploaded, see http://www.472khz.=
org/SlowJT9/.

Changes:
- PSKreporter.info spotting added.
- Flexible frequency boundaries for the spectrum display added (100 - 5000 =
Hz in 100 Hz steps).
- Help file added.

Bug reports, remarks and suggestions are welcome.

Next on my to-do list:

1. Run the recorded audio several times through the decoder with small "tim=
e-shift" steps.
I was intrigued by a mail from David, G0MRF,  (17 Januari):

"Last night was very good for propagation and TA activity on 630m.
It was one of those rare nights where signals were at a reasonable to good =
level, but unlike the previous several days, if not weeks, QSB was remarkab=
ly slow with only a few dB between peaks and troughs.  There was a period b=
etween 02.00 and 04.00 with no decodes here, but between 06:25 and 07:49 I =
decoded 19 transmissions from K9KFR in EN77, most of which were CQs
I was pleased to work Glenn VE9GJ on JT9 shortly after he made his first TA=
 QSO with Jan LA3EQ.
Interestingly Rik's SlowJT9 which was running in parallel, managed to decod=
e a couple of more transmissions than WSJT-X."

As I use the JT9 decoder from the WSJT-X suite the performance of SlowJT9 a=
nd WSJT-X should be identical. The only difference between both could be a =
small timing difference that made SlowJT9 to decode some extra transmission=
s (pure luck, it could have been the other way around as well).
So maybe the performance of SlowJT9 can be improved by running the recorded=
 audio several times through the decoder with each time a small (0.1 second=
 ?) time shift induced in the audio and then taking a "best off" all decode=
d signals.
I am not sure it will really help, but it seems worth to try.

2. Add optional internal frequency conversion to allow reception at higher =
frequencies
I have done some preliminary tests (based on the code snippet Wolf, DL4YHF,=
 sent me) and it seems to work fine.
But I am not sure that it will be very useful as frequency conversion will =
not increase the usable frequeny range, but just shit it.
Eg: now JT9-10 can be received from 100 Hz to 415 Hz audio. After USB downc=
onversion with a 1 kHz carrier the range will be 1100 Hz to 1415 Hz.
The only reason I can think of to want frequency conversion is if you use a=
 fixed frequency (ofen 800Hz) CW filter, so you can fit the JT9-5 or JT9-10=
 frequency range into the filter passband.
But this downconversion requires a Hilbert transform (90 degrees all pass f=
ilter) that never can be perfect and this will cause some distortion (in pa=
rticular at the lower and of the passband).
So before I start the effort to implement this in SlowJT9 I would like to k=
now if there is an audience for it.

73, Rik  ON7YD - OR7T

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Dear all,<br>
<br>
Beta-release v0.9.15.0 of SlowJT9 has been uploaded, see <a href=3D"http://=
www.472khz.org/SlowJT9/" target=3D"_blank">
http://www.472khz.org/SlowJT9/</a>.<br>
<br>
Changes:<br>
- PSKreporter.info spotting added.<br>
- Flexible frequency boundaries for the spectrum display added (100 - 5000 =
Hz in 100 Hz steps).<br>
- Help file added.<br>
<br>
Bug reports, remarks and suggestions are welcome.<br>
<br>
Next on my to-do list:<br>
<br>
<strong style=3D"text-decoration: underline;">1. Run the recorded audio sev=
eral times through the decoder with small &quot;time-shift&quot; steps.</st=
rong><br>
I was intrigued by a mail from David, G0MRF,&nbsp; (17 Januari):
<div><br>
&quot;<em style=3D"color: rgb(0, 111, 201); text-decoration: none solid rgb=
(0, 111, 201);"><span style=3D"color: rgb(0, 111, 201); text-decoration: no=
ne solid rgb(0, 111, 201);">Last night was very good for propagation and TA=
 activity on 630m.</span></em><br style=3D"color: rgb(0, 111, 201); text-de=
coration: none solid rgb(0, 111, 201);">
<em style=3D"color: rgb(0, 111, 201); text-decoration: none solid rgb(0, 11=
1, 201);"><span style=3D"color: rgb(0, 111, 201); text-decoration: none sol=
id rgb(0, 111, 201);">It was one of those rare nights where signals were at=
 a reasonable to good level, but unlike
 the previous several days, if not weeks, QSB was remarkably slow with only=
 a few dB between peaks and troughs.&nbsp; There was a period between 02.00=
 and 04.00 with no decodes here, but between 06:25 and 07:49 I decoded 19 t=
ransmissions from K9KFR in EN77, most
 of which were CQs</span></em><br style=3D"color: rgb(0, 111, 201); text-de=
coration: none solid rgb(0, 111, 201);">
<em style=3D"color: rgb(0, 111, 201); text-decoration: none solid rgb(0, 11=
1, 201);"><span style=3D"color: rgb(0, 111, 201); text-decoration: none sol=
id rgb(0, 111, 201);">I was pleased to work Glenn VE9GJ on JT9 shortly afte=
r he made his first TA QSO with Jan
 LA3EQ.</span></em><br style=3D"color: rgb(0, 111, 201); text-decoration: n=
one solid rgb(0, 111, 201);">
<em style=3D"color: rgb(0, 111, 201); text-decoration: none solid rgb(0, 11=
1, 201);"><span style=3D"color: rgb(0, 111, 201); text-decoration: none sol=
id rgb(0, 111, 201);"><strong>Interestingly Rik's SlowJT9 which was running=
 in parallel, managed to decode a couple
 of more transmissions than WSJT-X</strong>.</span></em>&quot;<br>
<br>
As I use the JT9 decoder from the WSJT-X suite the performance of SlowJT9 a=
nd WSJT-X should be identical. The only difference between both could be a =
small timing difference that made SlowJT9 to decode some extra transmission=
s (pure luck, it could have been
 the other way around as well).&nbsp;</div>
<div>So maybe the performance of SlowJT9 can be improved by&nbsp;running th=
e recorded audio several times through the decoder with each time a small (=
0.1 second ?) time shift induced in the audio and then taking a &quot;best =
off&quot; all decoded signals.</div>
<div>I am not sure it will really help, but it seems worth to try.</div>
<div><br>
</div>
<div style=3D"text-decoration: underline;"><strong>2. Add optional internal=
 frequency conversion to allow reception at higher frequencies</strong></di=
v>
<div>I have done some preliminary tests (based on the code snippet&nbsp;Wol=
f, DL4YHF, sent&nbsp;me) and it seems to work fine.<br>
</div>
<div>But I am not sure that it will be very useful as frequency conversion =
will not increase the usable frequeny range, but just shit it.<br>
</div>
<div>Eg: now JT9-10 can be received from 100 Hz to 415 Hz audio. After USB =
downconversion with a 1 kHz carrier the range will be 1100 Hz to 1415 Hz.<b=
r>
</div>
<div>The only reason&nbsp;I can think of to&nbsp;want frequency conversion =
is if you use a fixed frequency (ofen 800Hz) CW filter, so you can fit the =
JT9-5 or JT9-10&nbsp;frequency range into the filter&nbsp;passband.<br>
</div>
<div>But this downconversion requires a Hilbert transform (90 degrees all p=
ass filter) that never can be perfect and this will cause some distortion (=
in particular at the lower and of the passband).<br>
</div>
<div>So before I start&nbsp;the effort to implement this in SlowJT9 I would=
 like to know if there is an audience for it.<br>
</div>
<div>
<div><br>
</div>
<div>73, Rik&nbsp; ON7YD - OR7T<br>
</div>
</div>
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