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Date: Mon, 1 Mar 2010 00:05:35 +0000 (GMT)
From: M0FMT <m0fmt@yahoo.co.uk>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: VLF TX experiments_short report
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Hi Stefan and Group
=A0
The EU storms were in the UK news today quite amazing. Thanks for the upda=
te on the Dreamer's band ...hee.:-))
=A0
I have done some measurements on my toroid which if you have time to look=
 at I will send to you direct. Probably late tomorrow busy during the day=
 on other things.
=A0
I was going to do a range test with what I have got but the weather here=
 was too miserable to spend time standing on a hill waving a wire in the=
 air and getting soaking wet.=20

73 es GL petefmt

--- On Sun, 28/2/10, Stefan Sch=E4fer <schaefer@hst.tu-darmstadt.de> wrote=
:


From: Stefan Sch=E4fer <schaefer@hst.tu-darmstadt.de>
Subject: LF: VLF TX experiments_short report
To: rsgb_lf_group@blacksheep.org
Date: Sunday, 28 February, 2010, 23:08


Dear LF,=20

I am sorry that it was not possible to transmit today. Maybe you have hear=
d about the strong storm that damaged many trees and houses today. It woul=
dn't have been a good idea to be on the hill to that time..=20

A second problem was my DDS VFO. I saw that the duty cycle of the rectangu=
lar output was not 50%. So i had to modify the drivers circuit, adding a=
 CMOS4013 as a f divider and apply 2*f at it's input now.=20

What i wanted to use as the PA is a prototype of a SMPS that was designed=
 to operate at abt 50kHz. At 9kHz the ferrite core was already driven in=
 saturation. By varying the driving f i found, where the saturation occurs=
. Then i have known how many primary turns i have to spend at 9kHz. After=
 applying the new windings everything was right. But the time i had was go=
ne and the wind was already to strong. So i told Markus to inform you...

Now playing/increasing with the number of output windings of the SMPS tran=
sformer i applied the output voltage by a ordinary loudspeaker cable to th=
e primary air coil that is inductive coupled to the HV coil. I got 1,6kV=
 rms by applying 60W at the 12V DC input, really not much :-( But anyway=
 it will be suitable for a first test if a apply 6dB more power or so.

Lastly i have to get another coil that has more L and Q, so that no parall=
el C will be needed. I will try to do that in the next week. Tomorrow i do=
 not have to work and will spend time improving the PA (trying how much po=
wer is possible until the heat sink gets to warm and so on). Then, if the=
 wind will be not to strong any more, i will do some tests on the hill, me=
asuring R and C and so on...

Will keep you informed.

Rik, Pete, anything new dreamers records? Pete, have you increased your po=
wer? If you want i could send you a simple circuit for the PA, if you want=
. Dimensioning is really uncritical, switching losses as well, at those lo=
w frequencies. That's one of the advantages ;-)=20

GN es GL!! 73 de Stefan/DK7FC

PS: Just as 160m is called "Top band" we could call 9kHz the "Dreamers ban=
d". Sounds nice, isn't it? :-)




     =20

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<table cellspacing=3D"0" cellpadding=3D"0" border=3D"0" ><tr><td valign=3D=
"top" style=3D"font: inherit;"><DIV>Hi Stefan and Group</DIV>
<DIV>&nbsp;</DIV>
<DIV>The EU storms were in the UK news today quite amazing. Thanks for the=
 update on the Dreamer's band ...hee.:-))</DIV>
<DIV>&nbsp;</DIV>
<DIV>I have done some measurements on my toroid which if you have time to=
 look at I will send to you direct. Probably late tomorrow busy during the=
 day on other things.</DIV>
<DIV>&nbsp;</DIV>
<DIV>I was going to do a range test with what I have got but the weather=
 here was too miserable to spend time standing on a hill waving a wire in=
 the air and getting soaking wet. <BR><BR>73 es GL petefmt<BR><BR>--- On=
 <B>Sun, 28/2/10, Stefan Sch=E4fer <I>&lt;schaefer@hst.tu-darmstadt.de&gt;=
</I></B> wrote:<BR></DIV>
<BLOCKQUOTE style=3D"BORDER-LEFT: rgb(16,16,255) 2px solid; PADDING-LEFT:=
 5px; MARGIN-LEFT: 5px"><BR>From: Stefan Sch=E4fer &lt;schaefer@hst.tu-dar=
mstadt.de&gt;<BR>Subject: LF: VLF TX experiments_short report<BR>To: rsgb_=
lf_group@blacksheep.org<BR>Date: Sunday, 28 February, 2010, 23:08<BR><BR>
<DIV class=3DplainMail>Dear LF, <BR><BR>I am sorry that it was not possibl=
e to transmit today. Maybe you have heard about the strong storm that dama=
ged many trees and houses today. It wouldn't have been a good idea to be=
 on the hill to that time.. <BR><BR>A second problem was my DDS VFO. I saw=
 that the duty cycle of the rectangular output was not 50%. So i had to mo=
dify the drivers circuit, adding a CMOS4013 as a f divider and apply 2*f=
 at it's input now. <BR><BR>What i wanted to use as the PA is a prototype=
 of a SMPS that was designed to operate at abt 50kHz. At 9kHz the ferrite=
 core was already driven in saturation. By varying the driving f i found,=
 where the saturation occurs. Then i have known how many primary turns i=
 have to spend at 9kHz. After applying the new windings everything was rig=
ht. But the time i had was gone and the wind was already to strong. So i=
 told Markus to inform you...<BR><BR>Now playing/increasing with the numbe=
r of output
 windings of the SMPS transformer i applied the output voltage by a ordina=
ry loudspeaker cable to the primary air coil that is inductive coupled to=
 the HV coil. I got 1,6kV rms by applying 60W at the 12V DC input, really=
 not much :-( But anyway it will be suitable for a first test if a apply=
 6dB more power or so.<BR><BR>Lastly i have to get another coil that has=
 more L and Q, so that no parallel C will be needed. I will try to do that=
 in the next week. Tomorrow i do not have to work and will spend time impr=
oving the PA (trying how much power is possible until the heat sink gets=
 to warm and so on). Then, if the wind will be not to strong any more, i=
 will do some tests on the hill, measuring R and C and so on...<BR><BR>Wil=
l keep you informed.<BR><BR>Rik, Pete, anything new dreamers records? Pete=
, have you increased your power? If you want i could send you a simple cir=
cuit for the PA, if you want. Dimensioning is really uncritical, switching=
 losses as well,
 at those low frequencies. That's one of the advantages ;-) <BR><BR>GN es=
 GL!! 73 de Stefan/DK7FC<BR><BR>PS: Just as 160m is called "Top band" we=
 could call 9kHz the "Dreamers band". Sounds nice, isn't it? :-)<BR><BR></=
DIV></BLOCKQUOTE></td></tr></table><br>



     =20

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