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Date: Sun, 15 Dec 2013 21:17:23 +0100
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: A short VLF experiment at DK7FC
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Status: O

Hi Jay,

Am 15.12.2013 21:09, schrieb jrusgrove@comcast.net:
> Stefan
>
> What is the overall antenna R now?
On VLF? Well, i'm getting 850 mA at 400W, i.e. 550 Ohm. If i remember=20
correctly, the coil has 320 Ohm, so the sourrounding losses are 230 Ohm.

> With the kite of years gone by?
Who knows. At least there are no concrete plans in the moment. But it=20
would be nice :-)
The fixed antenna has some real advantages. But i will never generate a=20
signal in the range of 58 mW ERP with that one..
>
> Miss reading and seeing the pictures of your escapades in the field.
:-)

73, Stefan


>
> Jay W1VD  WD2XNS  WE2XGR/2  WG2XRS/2
>
>
> ----- Original Message ----- From: "Stefan Sch=E4fer"=20
> <Stefan.Schaefer@iup.uni-heidelberg.de>
> To: <rsgb_lf_group@blacksheep.org>; "Paul" <paul@abelian.netcom.co.uk>
> Sent: Sunday, December 15, 2013 11:33 AM
> Subject: Re: LF: A short VLF experiment at DK7FC
>
>
> Hi Peter, VLF,
>
> Did you see a trace on your grabber? Can you show me a link or a=20
> screenshot?
> The signal is well visible on Paul Nicholson's excellent VLF grabber,
> http://abelian.org/vlf/fbins.shtml#p=3D1387116000&b=3D110&s=3Dsp but fa=
r from
> stable. Is instability is due to my signal of course. Distance to Paul
> is 880 km, http://no.nonsense.ee/qth/map.html?qth=3DIO83XQ&from=3Djn49i=
k00wd
>
> You are right, there are many things to optimise. One thing is the
> housing of the PA. Now it is just mounted on a wooden plate. It is a H
> bridge using 4x IRFP460, switching directly at 230V*1.41, so the output
> of the PA is on mains potential! There is no galvanic decoupling
> transformer on the output (which would allow to use a grounded coax
> then) because such a transformer would have to be a VERY big ferrite
> core with many many turns (> 100). So the PA output is directly
> connected to the primary winding of the loading coil, which couples its
> field into the resonance winding (1200 turns). So the feed line is
> floating on an unknown voltage which depends on the capacitive coupling
> to sourrounding things. In the field experiments 2010/2011 this was no
> problem. But now it is. I guess this is causing EMC problems to the /2
> frequency divider, sometimes. Thus, i will put it into a metallic box
> which is grounded to earth potential.
>
> Another problem is the parallel capacitor which i have to add to come o=
n
> resonance. It's capacity is not high enough and i have to add about 10m
> or wire hanging arround. This additional wire is moving in the wind
> blasts and causes further instability of the signal (kind of AM due to
> modulated resonance peak, i.e. antenna current). Another way would be t=
o
> add more turns to the coil but this antenna system  is voltage limited
> and it doesn't matter at all if i have to put 400W or 500W into the=20
> system.
>
> BTW this night/day it was 850 mA antenna current and about 400W RF
> power. I will plan to do more QRO, when the new capacitor is ready to=20
> use.
>
> Here is an image of the arrangement, taken 30 minutes ago:
> https://dl.dropboxusercontent.com/u/19882028/VLF/20131215_165406.jpg
>
> As soon as the C of "DK7FC" is finished, i will run some OPDS32
> sequences for DF6NM and Paul Nicholson and others :-)
> BTW i have disconnected my VLF grabber antenna since the RX is
> overloaded anyway. Now it is easier to identify eventual phase glitches
> (could be on the RX side as well, though).
>
> 73 and thanks for watching.
>
> Stefan/DK7FC
>
>
>
> Am 15.12.2013 14:49, schrieb PA1SDB, Peter:
>> Stefan,
>> Signal is O.K., but stabillity is'nt :-(
>> To much spread around center frequency.
>>
>> (I know.... I'm complaining about 0.01 Hz drift..........)
>>
>> 73's Peter
>>
>>
>> ----- Original Message ----- From: "Stefan Sch=E4fer"=20
>> <Stefan.Schaefer@iup.uni-heidelberg.de>
>> To: <rsgb_lf_group@blacksheep.org>; "Paul" <paul@abelian.netcom.co.uk>
>> Sent: Sunday, December 15, 2013 4:14 AM
>> Subject: Re: LF: A short VLF experiment at DK7FC
>>
>>
>> Since 4:10 UTC, the signal is available without interruptions now on
>> 8.97000500 kHz.
>>
>> 73, Stefan/DK7FC
>>
>> Am 14.12.2013 20:50, schrieb Stefan Sch=E4fer:
>>> Hi all,
>>>
>>> Tomorrow the rain probability is just 10% and so i think i can risk=20
>>> to run a short VLF experiment on 8970.00500 Hz. I'm using the fixed=20
>>> antenna at JN49IK00WD. These days, the QRN is very low for quite a=20
>>> long time! The plan is to run about 500W RF power, or more,=20
>>> depending on the voltage limit of the antenna. And the plan is to=20
>>> start transmitting tonite, after the experiment with VO1NA, i.e.=20
>>> i'll come on air arround 2 UTC, hopefully. I will run the test until=20
>>> the late afternoon. First i'm TXing a stable frequency until 9 UTC,=20
>>> later some DFCW-600, and then maybe some tests in OPDS32.
>>> Suggestions welcome.
>>> BUT it all depends on the WX. If it starts to rain then i have to sto=
p.
>>> Will someone give it a try and watch for me?
>>>
>>> 73, Stefan/DK7FC
>>
>