Date: Thu, 8 Sep 2016 06:36:08 -0400
From: Markus Vester <markusvester@aol.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: OPDS bandwidth (was EA5DOM LF tests)
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Yes, Mike is right. Zooming the spectrogram on Luis' signal did not show an=
y central carrier, so subsequent dashes seem to have random phase. An addit=
ional problem could be the temperature drift of the master crystal oscillat=
or (neither the common 125 MHz-clocked AD9850 modules nor the Si570 source =
are very stable).=20

Regarding a new transmitter, I would recommend starting with a stable conti=
nuous signal from an OCXO or TCXO, and applying the keying only directly be=
fore the PA, after any divider stages. As far as I can see, this is done ri=
ght in the W1VD design, where the flipflop runs through and keying is appli=
ed to the FET drivers.

All the best,
Markus (DF6NM)

-----Urspr=C3=BCngliche Mitteilung-----=20
Von: Mike Dennison <mike.dennison@ntlworld.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Do, 8 Sept 2016 12:12 pm
Betreff: LF: OPDS bandwidth (was EA5DOM LF tests)


The wider bandwidth seen on OPDS may be key clicks but I have found=20
it can be caused by a non-coherent signal, ie the 'oscillator' is not=20
continuously running. I found this, for instance, when keying a=20
divider chip on my GW3UEP 472kHz rig, and it was cured by keying the=20
PA instead.

Mike, G3XDV
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

On 7 Sep 2016 at 11:20, DK7FC wrote:

> date time call distance frequency bandwidth snr=20
> correlation
>=20
> 2016-09-07 04:35:08 EA5DOM 1398km 137519.960Hz 97mHz -37.7dBOp 100%
> 20.2dB 2016-09-07 03:35:08 EA5DOM 1398km 137519.910Hz 112mHz
> -48.5dBOp 100% 19.8dB 2016-09-07 02:35:09 EA5DOM 1398km 137519.928Hz=20
> 75mHz -42.0dBOp 46% 16.6dB 2016-09-07 01:35:07 EA5DOM 1398km
> 137519.926Hz 71mHz -99.9dBOp 77% 16.6dB
>=20
>=20
> Somehow the bandwidth values are quite high. Normally it is arround <
> 10 mHz. Anyway, a nice result.
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<div style=3D"font-size:10pt;font-family:arial,helvetica,sans-serif;color:b=
lack;"><div style=3D"color: black; font-family: arial,helvetica,sans-serif;=
 font-size: 10pt;">Yes, Mike is right. Zooming the spectrogram&nbsp;on Luis=
' signal did not show&nbsp;any central carrier, so subsequent dashes&nbsp;s=
eem to have random phase. An additional problem could be the temperature dr=
ift of the master crystal oscillator (neither the common 125 MHz-clocked AD=
9850 modules nor the Si570 source are very stable). <br><br>Regarding a new=
 transmitter,&nbsp;I would recommend starting with a stable continuous sign=
al from an OCXO or TCXO, and applying the keying only directly before the P=
A, after any divider stages. As far as I can see, this is done right in the=
 W1VD design, where the flipflop runs through and&nbsp;keying is applied to=
 the FET drivers.<br><br>All the best,<br>Markus (DF6NM)<br><br>-----Urspr=
=C3=BCngliche Mitteilung----- <br>Von: Mike Dennison &lt;mike.dennison@ntlw=
orld.com&gt;<br>An: rsgb_lf_group &lt;rsgb_lf_group@blacksheep.org&gt;<br>V=
erschickt: Do, 8 Sept 2016 12:12 pm<br>Betreff: LF: OPDS bandwidth (was EA5=
DOM LF tests)<br><br></div>The wider bandwidth seen on OPDS may be key clic=
ks but I have found <br>it can be caused by a non-coherent signal, ie the '=
oscillator' is not <br>continuously running. I found this, for instance, wh=
en keying a <br>divider chip on my GW3UEP 472kHz rig, and it was cured by k=
eying the <br>PA instead.<br><br>Mike, G3XDV<br>=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D<br><br>On 7 Sep 2016 at 11:20, DK7FC wrote:<br><br>&gt;     date =
     time   call   distance  frequency bandwidth  snr   <br>&gt;     correl=
ation<br>&gt; <br>&gt; 2016-09-07 04:35:08 EA5DOM  1398km 137519.960Hz  97m=
Hz -37.7dBOp 100%<br>&gt; 20.2dB 2016-09-07 03:35:08 EA5DOM  1398km 137519.=
910Hz 112mHz<br>&gt; -48.5dBOp 100% 19.8dB 2016-09-07 02:35:09 EA5DOM  1398=
km 137519.928Hz <br>&gt; 75mHz -42.0dBOp  46% 16.6dB 2016-09-07 01:35:07 EA=
5DOM  1398km<br>&gt; 137519.926Hz  71mHz -99.9dBOp  77% 16.6dB<br>&gt; <br>=
&gt; <br>&gt; Somehow the bandwidth values are quite high. Normally it is a=
rround &lt;<br>&gt; 10 mHz. Anyway, a nice result.<br><br><br></div>
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