Message-ID: <4E01DE94.1050405@iup.uni-heidelberg.de>
Date: Wed, 22 Jun 2011 14:22:44 +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
References: <4DFE5EA9.2090101@iup.uni-heidelberg.de>	<9B4318767B6849FFB89F8294D336ACEC@White> <BANLkTi=0cyXuU-ZRfXQUP6En91MWyD7eGg@mail.gmail.com> <4DFF094E.6070008@iup.uni-heidelberg.de> <DB1AF20F204E4F89964218DC6B852003@White>
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Subject: Re: VLF: DF6NM kite activity June 19
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Hello Markus, VLF,

Am 21.06.2011 00:00, schrieb Markus Vester:
> Total resistance of the antenna circuit was around 280 ohms (including=20
> 140 ohms for the coil). This is about half of that when I used the=20
> same kite antenna in Bamberg with only a few short ground pegs.
Excellent! I wish to have such a low earth resistance. Also 140 Ohms for=20
the coil is very good. Mine has 185 Ohm for 190 mH but therefore no HV=20
problems so far, even at 1.7 A antenna current (in the 10th exp during=20
the CW transmissions)
> BTW all seven buckets connected to 900 pF resonate at about 4.6 kHz -=20
> Stefan, how about a 65 km band ;-)
65 km sounds good! ;-) Would be the lowest frequency ever. You should be=20
the first one to transmit there. If you early announce such a test i=20
would run a "DFCW-2400" window on 4600 Hz.
But as we planned, we should think about coupling our coils in a common=20
meeting, maybe on my 12th experiment. You seem to have 1.3 H. Coupling=20
with my 550 mH coil may achieve 2 H. If we would use my 300m vertical=20
which has about 1650 pF we could transmit on 2.77 kHz, ULF, the 108 km=20
band! :-) What do you think? We could generate about 7 mW ERP!
> On my own grabber, I attempted to compare signal levels from DK7FC=20
> (-71 dB, 180 km) and myself (-43 dB, 4.5 km). Correcting this=20
> difference (28 dB) by the EMRP ratio (26 mW / 1.2 mW =3D 13 dB),=20
> distance ratio (1/r =3D 32 dB) plus an additional nearfield correction=20
> (1/r=B3 instead of 1/r from 4.5 to 5.3 km =3D 3 dB), we find that Stefa=
n=20
> was 28+13-35 dB =3D 6 dB weaker than we would expect by pure groundwave=
.=20
> This corresponds very well to the earlier experience that there is a=20
> midday skywave cancellation effect for about 200 km.
Interesting!

73, Stefan/DK7FC


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Hello Markus, VLF,<br>
<br>
Am 21.06.2011 00:00, schrieb Markus Vester:
<blockquote cite="mid:DB1AF20F204E4F89964218DC6B852003@White"
 type="cite">
  <title></title>
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  <div><font face="Arial" size="2">Total resistance of the antenna
circuit was around 280 ohms (including 140 ohms for the coil). This is
about half of&nbsp;that&nbsp;when I used the same kite antenna&nbsp;in Bamberg with
only a few short ground pegs.</font></div>
</blockquote>
Excellent! I wish to have such a low earth resistance. Also 140 Ohms
for the coil is very good. Mine has 185 Ohm for 190 mH but therefore no
HV problems so far, even at 1.7 A antenna current (in the 10th exp
during the CW transmissions)<br>
<blockquote cite="mid:DB1AF20F204E4F89964218DC6B852003@White"
 type="cite">
  <div>&nbsp;</div>
  <div><font face="Arial" size="2">BTW&nbsp;all&nbsp;seven buckets connected to
900 pF&nbsp;resonate&nbsp;at about 4.6 kHz - Stefan, how about a 65 km band ;-)</font></div>
</blockquote>
65 km sounds good! ;-) Would be the lowest frequency ever. You should
be the first one to transmit there. If you early announce such a test i
would run a "DFCW-2400" window on 4600 Hz.<br>
But as we planned, we should think about coupling our coils in a common
meeting, maybe on my 12th experiment. You seem to have 1.3 H. Coupling
with my 550 mH coil may achieve 2 H. If we would use my 300m vertical
which has about 1650 pF we could transmit on 2.77 kHz, ULF, the 108 km
band! :-) What do you think? We could generate about 7 mW ERP!<br>
<blockquote cite="mid:DB1AF20F204E4F89964218DC6B852003@White"
 type="cite">
  <div><font face="Arial" size="2">On my own grabber, I attempted
to&nbsp;compare&nbsp;signal levels from&nbsp;DK7FC (-71 dB, 180 km) and myself (-43
dB, 4.5 km).&nbsp;Correcting this difference (28 dB) by&nbsp;the EMRP ratio (26
mW&nbsp;/ 1.2 mW = 13 dB), distance ratio (1/r = 32 dB)&nbsp;plus&nbsp;an
additional&nbsp;nearfield correction (1/r&sup3; instead of 1/r from 4.5 to 5.3
km&nbsp;= 3 dB), we&nbsp;find that Stefan was</font><font face="Arial" size="2">&nbsp;28+13-35
dB = 6 dB weaker than we would expect by pure groundwave. This
corresponds very well to the earlier experience that there is a midday
skywave cancellation effect for about 200 km.</font></div>
</blockquote>
Interesting! <br>
<br>
73, Stefan/DK7FC<br>
<br>
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