Message-ID: <4F7F03A4.8080000@iup.uni-heidelberg.de>
Date: Fri, 06 Apr 2012 16:54:28 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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To: rsgb_lf_group@blacksheep.org
CC: Paul <paul@abelian.netcom.co.uk>
References: <CAHAQVWMHwxmWAPqTVxgdAK-h35BLbu5QOkD9eKEe37P=hAhkCg@mail.gmail.com> <4F78CCE0.5050906@iup.uni-heidelberg.de>
In-Reply-To: <4F78CCE0.5050906@iup.uni-heidelberg.de>
Subject: Re: LF: LOPTs
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VLF,

The LOPT still works, seems to be no problem. Just a FET was sk. Somehow=20
all the previous problems are gone now and i am getting about 2 kV rms=20
from the transformer. So i stopped my LF beacon on 137 and QSYed to=20
8.97000 kHz. I also found the problem why my last transmission had so=20
many phase glitches. Now the PC is locked to GPS again. The PA takes=20
about 15 W input power, no not much DX is to be expected, just a local=20
test. I do some tests with the VLF active E probe now, receiving my own=20
signal in some distance and compare the S/N from the forest and a flat=20
field.
I think Paul can't receive my weak signal but we've often been wrong=20
with such assumptions :-)

BTW i'm transmitting DFCW-600 centered at 8970.00000 Hz, so i should be=20
outside eventual other VLF tests by DF6NM.

73, Stefan/DK7FC

PS: If all works well with the transformer over a longer period, i=20
intend to run a stable carrier over several days or transmit ma full=20
call in DFCW-60000 or so :-) But the signal is 20 dB stronger with the=20
big coil and another 20 dB stronger with the 300m kite...


Am 01.04.2012 23:47, schrieb Stefan Sch=E4fer:
> Hi Roger,
>
> Well, they are not as suitable as i expected. Just a few kV can be=20
> generated and applied to the wire. But that's fine for local tests. I=20
> didn't measure the L but rather tried to find a resonance. I took two=20
> 1 nF capacitors and a 50 Ohm resistor in series to make an equivalent=20
> circuit of my antenna for tests in the shack. I built a class D PA out=20
> of the transformer, running at low input voltage and tried to find the=20
> resonance. But there was no clear resonance. The output waveform looks=20
> very different to a sine wave :-) Probably this is due to internal=20
> winding capacitances, no idea. At least i spend a lot of time and do=20
> not want to spend even more time on the LOPT project.
> A few weeks ago i tried some local tests with WOLF10 and got a decode=20
> in 950m distance, which is close in the near field, so not really=20
> exciting. I just want to go on a bit with these tests but i won't go=20
> on much longer with the tests. The standard QRSS or DFCW or MFSK=20
> analog modes, readout by a human is just the best in my opinion.
>
> 73, Stefan
>
>
>
> Am 01.04.2012 22:35, schrieb Roger Lapthorn:
>> Stefan et al,
>>
>> Not being too familiar with LOPTs what inductance are the windings?=20
>> Are there particular non-encapsulated types that would be more=20
>> suitable for compact loading coils for lower powered 8.97kHz E-field=20
>> TX antennas?
>>
>> 73s
>> Roger G3XBM
>>
>> --=20
>> http://qss2.blogspot.com/
>> http://g3xbm-qrp.blogspot.com/
>> http://www.g3xbm.co.uk
>> https://sites.google.com/site/sub9khz/
>>
>>

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VLF, <br>
<br>
The LOPT still works, seems to be no problem. Just a FET was sk.
Somehow all the previous problems are gone now and i am getting about 2
kV rms from the transformer. So i stopped my LF beacon on 137 and QSYed
to 8.97000 kHz. I also found the problem why my last transmission had
so many phase glitches. Now the PC is locked to GPS again. The PA takes
about 15 W input power, no not much DX is to be expected, just a local
test. I do some tests with the VLF active E probe now, receiving my own
signal in some distance and compare the S/N from the forest and a flat
field.<br>
I think Paul can't receive my weak signal but we've often been wrong
with such assumptions :-)<br>
<br>
BTW i'm transmitting DFCW-600 centered at 8970.00000 Hz, so i should be
outside eventual other VLF tests by DF6NM.<br>
<br>
73, Stefan/DK7FC<br>
<br>
PS: If all works well with the transformer over a longer period, i
intend to run a stable carrier over several days or transmit ma full
call in DFCW-60000 or so :-) But the signal is 20 dB stronger with the
big coil and another 20 dB stronger with the 300m kite...<br>
<br>
<br>
Am 01.04.2012 23:47, schrieb Stefan Sch&auml;fer:
<blockquote cite="mid:4F78CCE0.5050906@iup.uni-heidelberg.de"
 type="cite">
  <meta content="text/html; charset=ISO-8859-1"
 http-equiv="Content-Type">
Hi Roger, <br>
  <br>
Well, they are not as suitable as i expected. Just a few kV can be
generated and applied to the wire. But that's fine for local tests. I
didn't measure the L but rather tried to find a resonance. I took two 1
nF capacitors and a 50 Ohm resistor in series to make an equivalent
circuit of my antenna for tests in the shack. I built a class D PA out
of the transformer, running at low input voltage and tried to find the
resonance. But there was no clear resonance. The output waveform looks
very different to a sine wave :-) Probably this is due to internal
winding capacitances, no idea. At least i spend a lot of time and do
not want to spend even more time on the LOPT project. <br>
A few weeks ago i tried some local tests with WOLF10 and got a decode
in 950m distance, which is close in the near field, so not really
exciting. I just want to go on a bit with these tests but i won't go on
much longer with the tests. The standard QRSS or DFCW or MFSK analog
modes, readout by a human is just the best in my opinion.<br>
  <br>
73, Stefan<br>
  <br>
  <br>
  <br>
Am 01.04.2012 22:35, schrieb Roger Lapthorn:
  <blockquote
 cite="mid:CAHAQVWMHwxmWAPqTVxgdAK-h35BLbu5QOkD9eKEe37P=hAhkCg@mail.gmail.com"
 type="cite">Stefan et al,<br>
    <br>
Not being too familiar with LOPTs what inductance are the windings? Are
there particular non-encapsulated types that would be more suitable for
compact loading coils for lower powered 8.97kHz E-field TX antennas?<br>
    <br>
73s<br>
Roger G3XBM<br clear="all">
    <br>
-- <br>
    <font color="#888888"> </font><font color="#888888"><a
 moz-do-not-send="true" href="http://qss2.blogspot.com/" target="_blank">http://qss2.blogspot.com/</a><br>
    </font><font color="#888888"><a moz-do-not-send="true"
 href="http://g3xbm-qrp.blogspot.com/" target="_blank">http://g3xbm-qrp.blogspot.com/</a></font><br>
    <font color="#888888"><a moz-do-not-send="true"
 href="http://www.g3xbm.co.uk" target="_blank">http://www.g3xbm.co.uk</a><br>
    <a moz-do-not-send="true"
 href="https://sites.google.com/site/sub9khz/" target="_blank">https://sites.google.com/site/sub9khz/</a><br>
    <br>
    </font><br>
  </blockquote>
</blockquote>
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