Message-ID: <004901cd98f7$83a47670$0501a8c0@xphd97xgq27nyf>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <505E0C74.9040704@iup.uni-heidelberg.de>
Date: Sat, 22 Sep 2012 19:21:49 -0000
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Subject: LF: Re: JT-8 !
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This is wonderful progress there will soon be one Data mode for each LF =
es MF operator
Like ships passing in he night !!
de g3kev

  ----- Original Message -----=20
  From: Stefan Sch=E4fer=20
  To: rsgb_lf_group@blacksheep.org=20
  Sent: Saturday, September 22, 2012 7:07 PM
  Subject: LF: JT-8 !


  FYI, message from Joe/K1JT  (permission to forward it to the group).

  73, Stefan/DK7FC

  -------- Original-Nachricht -------- Betreff:  Re: Fwd: LF: =
Experimental software for WSPR-8 and -32=20
        Datum:  Sat, 22 Sep 2012 14:11:10 -0400=20
        Von:  Joe Taylor=20
      =20
        An:  Stefan Sch=E4fer=20
  [...]


I had some free time recently to think further about a more sensitive=20
mode for MF and LF use.  Here is a very brief and preliminary planning=20
statement, including simulation results for the decoding thresholds that =

should be reached.

############################## JT8 ###################################

JT8 is a mode designed for amateur QSOs and beacon-like transmissions at =

MF and LF.  The mode uses the same 72-bit user messages as JT65,=20
augmented by a 12-bit cyclic redundancy check (CRC).  Error-control=20
coding uses a convolutional code with constraint length K=3D16, rate=20
r=3D1/2, and a zero tail, leading to an encoded message length of=20
(72+12+15)*2 =3D 198 bits.  Modulation is 8-FSK, so a transmission=20
requires 198/3 =3D 66 information-carrying channel symbols.  Two 8x8=20
Costas arrays are added to each transmission for purposes of time and=20
frequency synchronization.  A full transmission thus contains 66 + 16 =
=3D=20
82 symbols.  Tone spacing df of the 8-FSK modulation is equal to the=20
keying rate; symbol duration tsym =3D 1/df, and the total occupied=20
bandwidth is 8*df.  The actual transmission length TxT is slightly less=20
than the T/R sequence time, to allow for possible message decoding=20
before the next transmission starts.

Parameters of the five JT8 sub-modes are summarized in the following=20
table, along with S/N thresholds measured by simulation on an AWGN=20
(additive white Gaussian noise) channel.

Mode   T/R   TxT    df    tsym   BW    S/N*
       (m)   (s)   (Hz)    (s)  (Hz)   (dB)
-----------------------------------------------
JT8-1    1    52  1.577   0.63  12.6  -26.9
JT8-2    2   112  0.732   1.37   5.9  -30.2
JT8-5    5   292  0.281   3.56   2.2  -34.4
JT8-10  10   592  0.139   7.22   1.1  -37.5
JT8-30  30  1792  0.046  21.85   0.4  -42.3
-----------------------------------------------
* Noise power measured in a 2500 Hz bandwidth.

########################################################################

As you can see, with 2-minute transmissions JT8-2 has 1-2 dB better=20
sensitivity than WSPR.  This is because 8-FSK is more efficient than=20
4-FSK and because in JT8 less Tx energy is "wasted" on the=20
synchronization task.  JT8-30 does about 12 dB better than JT8-2.

As time is available in coming weeks, I hope to start some coding.

Your comments would of course be welcome!

	-- 73, Joe, K1JT



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<DIV><FONT face=3DArial>This is wonderful progress there will soon be =
one Data=20
mode for each LF es MF operator</FONT></DIV>
<DIV><FONT face=3DArial>Like ships passing in he night !!</FONT></DIV>
<DIV><FONT face=3DArial>de g3kev</FONT></DIV>
<DIV>&nbsp;</DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
  <A title=3DStefan.Schaefer@iup.uni-heidelberg.de=20
  href=3D"mailto:Stefan.Schaefer@iup.uni-heidelberg.de">Stefan =
Sch=E4fer</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Drsgb_lf_group@blacksheep.org=20
  =
href=3D"mailto:rsgb_lf_group@blacksheep.org">rsgb_lf_group@blacksheep.org=
</A>=20
  </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Saturday, September 22, =
2012 7:07=20
  PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> LF: JT-8 !</DIV>
  <DIV><BR></DIV>FYI, message from Joe/K1JT&nbsp; (permission to forward =
it to=20
  the group).<BR><BR>73, Stefan/DK7FC<BR><BR>-------- Original-Nachricht =

  --------=20
  <TABLE class=3Dmoz-email-headers-table cellSpacing=3D0 cellPadding=3D0 =
border=3D0>
    <TBODY>
    <TR>
      <TH vAlign=3Dbaseline noWrap align=3Dright>Betreff: </TH>
      <TD>Re: Fwd: LF: Experimental software for WSPR-8 and =
-32</TD></TR>
    <TR>
      <TH vAlign=3Dbaseline noWrap align=3Dright>Datum: </TH>
      <TD>Sat, 22 Sep 2012 14:11:10 -0400</TD></TR>
    <TR>
      <TH vAlign=3Dbaseline noWrap align=3Dright>Von: </TH>
      <TD>Joe Taylor <BR></TD></TR>
    <TR>
      <TH vAlign=3Dbaseline noWrap align=3Dright>An: </TH>
      <TD>Stefan =
Sch=E4fer</TD></TR></TBODY></TABLE><I>[...]</I><BR><PRE>
I had some free time recently to think further about a more sensitive=20
mode for MF and LF use.  Here is a very brief and preliminary planning=20
statement, including simulation results for the decoding thresholds that =

should be reached.

############################## JT8 ###################################

JT8 is a mode designed for amateur QSOs and beacon-like transmissions at =

MF and LF.  The mode uses the same 72-bit user messages as JT65,=20
augmented by a 12-bit cyclic redundancy check (CRC).  Error-control=20
coding uses a convolutional code with constraint length K=3D16, rate=20
r=3D1/2, and a zero tail, leading to an encoded message length of=20
(72+12+15)*2 =3D 198 bits.  Modulation is 8-FSK, so a transmission=20
requires 198/3 =3D 66 information-carrying channel symbols.  Two 8x8=20
Costas arrays are added to each transmission for purposes of time and=20
frequency synchronization.  A full transmission thus contains 66 + 16 =
=3D=20
82 symbols.  Tone spacing df of the 8-FSK modulation is equal to the=20
keying rate; symbol duration tsym =3D 1/df, and the total occupied=20
bandwidth is 8*df.  The actual transmission length TxT is slightly less=20
than the T/R sequence time, to allow for possible message decoding=20
before the next transmission starts.

Parameters of the five JT8 sub-modes are summarized in the following=20
table, along with S/N thresholds measured by simulation on an AWGN=20
(additive white Gaussian noise) channel.

Mode   T/R   TxT    df    tsym   BW    S/N*
       (m)   (s)   (Hz)    (s)  (Hz)   (dB)
-----------------------------------------------
JT8-1    1    52  1.577   0.63  12.6  -26.9
JT8-2    2   112  0.732   1.37   5.9  -30.2
JT8-5    5   292  0.281   3.56   2.2  -34.4
JT8-10  10   592  0.139   7.22   1.1  -37.5
JT8-30  30  1792  0.046  21.85   0.4  -42.3
-----------------------------------------------
* Noise power measured in a 2500 Hz bandwidth.

########################################################################

As you can see, with 2-minute transmissions JT8-2 has 1-2 dB better=20
sensitivity than WSPR.  This is because 8-FSK is more efficient than=20
4-FSK and because in JT8 less Tx energy is "wasted" on the=20
synchronization task.  JT8-30 does about 12 dB better than JT8-2.

As time is available in coming weeks, I hope to start some coding.

Your comments would of course be welcome!

	-- 73, Joe, K1JT
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