Date: Wed, 24 Dec 2014 16:08:04 +0100
From: uwe-jannsen@kabelmail.de
To: rsgb_lf_group@blacksheep.org
Message-ID: <99fd31f5ff034c43939abece11c26fb7@kabelmail.de>
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Subject: Re: Re: VLF: 8270 Hz BPSK
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Paul, Markus,=20

OK:, new constellation: =20

Code:Rate 1/18 K =3D 25
 Characters: 25
 10sec/symb
 1520 signal bits
 duration: 4h14sec =20

TX time: 11:00 to 16:00, day: when the WX will be fine=2E=20

Uwe/dj8wx=20

Von: rsgb_lf_group@blacksheep=2Eorg
 Gesendet: 22=2E12=2E2014 21:59
 An: rsgb_lf_group@blacksheep=2Eorg
 Betreff: Re: VLF: 8270 Hz BPSK

 Uwe wrote:

 > I would prefer Rate 1/8K =3D 25 out of your convolution code
 > message generator, i=2Ee=2E 560bits in 4h40min=2E

 Your last transmission I think was on 2014-11-07 and I just
 examined the recording: You were S/N 14=2E7dB in 278uHz between
 12:00 and 14:00=2E Signal is strong enough to send data quite
 fast=2E You could use 14 second symbols to send 10 characters
 (800 signal bits in 03:06:40) for a virtually certain decode=2E

 A more challenging test with 11 second symbols would still
 have 95% chance of correct decode=2E

 So far the best radio amateur message transmission at VLF was
 by Markus DF6NM on 2014-05-18 when he sent 14 characters across
 1028km=2E If we use product of distance and characters as a metric
 then that's a score of 14392 kmchars=2E

 At 762km you would have to send 19 or more characters to beat
 that=2E Daytime should allow a 4 hour message without trouble=2E
 Rate 1/8, 11 second symbols, 21 characters (1328 bits in 04:03:28)=2E
 Avoid the terminators=2E Send around midday +/- 2 hours=2E

 On 2014-12-14 I wrote:

 > http://abelian=2Eorg/vlf/tmp/141219c=2Epng

 > From 00:00 to 08:00 it averaged 12=2E6dB S/N in 278uHz, 0=2E14fT=2E
 > That's enough signal to send 27 characters at a rate of 22
 > information bits per hour=2E

 I gave this a test using a recording of W4DEX carrier from
 that night=2E Modulating the recording with a BPSK message 27
 characters long, rate 1/16 K=3D25 with a symbol period of only 7=2E5
 seconds and it decoded correctly with a small margin to spare=2E
 9 second symbols decoded with plenty of margin=2E

 --
 Paul Nicholson
 http://abelian=2Eorg/
 --
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<div style=3D"margin: 5px;padding:0;font-family: Arial; font-size: 13px=
;"><p>Paul, Markus,</p>
<p><span>OK:, new constellation:</span> </p>
<p><span></span><span>Code:Rate 1/18 K =3D 25<br />
Characters: 25</span><span><br />
10sec/symb<br />
1520 signal bits</span><span><br />
duration: 4h14sec</span> </p>
<p><span>TX time: </span><span>11:00 to 16:00</span><span>, day: when t=
he WX will be fine=2E</span></p>
<p><span></span><span>Uwe/dj8wx</span></p>
<div style=3D"background-color: #f9f9f9; line-height: 20px; padding: 5p=
x; border-top: 1px solid #dfdfdf;" class=3D"replyHeader"><strong style=3D=
"width: 80px; display: inline-block; font-size: 95%;">Von:</strong> rsg=
b_lf_group@blacksheep=2Eorg<br />
<strong style=3D"width: 80px; display: inline-block; font-size: 95%;">G=
esendet:</strong> 22=2E12=2E2014 21:59<br />
<strong style=3D"width: 80px; display: inline-block; font-size: 95%;">A=
n:</strong> rsgb_lf_group@blacksheep=2Eorg<br />
<strong style=3D"width: 80px; display: inline-block; font-size: 95%;">B=
etreff:</strong> Re: VLF: 8270 Hz BPSK<br />
</div>
<br />
Uwe wrote:<br />
<br />
&gt; I would prefer Rate 1/8K =3D 25 out of your convolution code<br />
&gt; message generator, i=2Ee=2E  560bits in 4h40min=2E<br />
<br />
Your last transmission I think was on 2014-11-07 and I just<br />
examined the recording:  You were S/N 14=2E7dB in 278uHz between<br />
12:00 and 14:00=2E  Signal is strong enough to send data quite<br />
fast=2E  You could use 14 second symbols to send 10 characters<br />
(800 signal bits in 03:06:40) for a virtually certain decode=2E<br />
<br />
A more challenging test with 11 second symbols would still<br />
have 95% chance of correct decode=2E<br />
<br />
So far the best radio amateur message transmission at VLF was<br />
by Markus DF6NM on 2014-05-18 when he sent 14 characters across<br />
1028km=2E  If we use product of distance and characters as a metric<br =
/>
then that's a score of 14392 kmchars=2E<br />
<br />
At 762km you would have to send 19 or more characters to beat<br />
that=2E   Daytime should allow a 4 hour message without trouble=2E<br /=
>
Rate 1/8, 11 second symbols, 21 characters (1328 bits in 04:03:28)=2E<b=
r />
Avoid the terminators=2E Send around midday +/- 2 hours=2E<br />
<br />
On 2014-12-14 I wrote:<br />
<br />
&gt;  http://abelian=2Eorg/vlf/tmp/141219c=2Epng<br />
<br />
&gt; From 00:00 to 08:00 it averaged 12=2E6dB S/N in 278uHz, 0=2E14fT=2E=
<br />
&gt; That's enough signal to send 27 characters at a rate of 22<br />
&gt; information bits per hour=2E<br />
<br />
I gave this a test using a recording of W4DEX carrier from<br />
that night=2E  Modulating the recording with a BPSK message 27<br />
characters long, rate 1/16 K=3D25 with a symbol period of only 7=2E5<br=
 />
seconds and it decoded correctly with a small margin to spare=2E<br />
9 second symbols decoded with plenty of margin=2E<br />
<br />
--<br />
Paul Nicholson<br />
http://abelian=2Eorg/<br />
--<br /></div>
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