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Re: LF: A short VLF experiment at DK7FC

To: "[email protected]" <[email protected]>
Subject: Re: LF: A short VLF experiment at DK7FC
From: Laurence KL7 L <[email protected]>
Date: Sun, 15 Dec 2013 11:27:02 -1000
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Is this the same coil as used for the kites stefan?

Laurence in KH6
Lightning storm 29C


> On Dec 15, 2013, at 10:19 AM, "Stefan Schäfer" 
> <[email protected]> wrote:
> 
> Hi Jay,
> 
> Am 15.12.2013 21:09, schrieb [email protected]:
>> 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 
> 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 would 
> be nice :-)
> The fixed antenna has some real advantages. But i will never generate a 
> 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 Schäfer" 
>> <[email protected]>
>> To: <[email protected]>; "Paul" <[email protected]>
>> 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 screenshot?
>> The signal is well visible on Paul Nicholson's excellent VLF grabber,
>> http://abelian.org/vlf/fbins.shtml#p=1387116000&b=110&s=sp but far 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=IO83XQ&from=jn49ik00wd
>> 
>> 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 on
>> 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 to
>> 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 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 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 Schäfer" 
>>> <[email protected]>
>>> To: <[email protected]>; "Paul" <[email protected]>
>>> 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 Schäfer:
>>>> Hi all,
>>>> 
>>>> Tomorrow the rain probability is just 10% and so i think i can risk to run 
>>>> a short VLF experiment on 8970.00500 Hz. I'm using the fixed antenna at 
>>>> JN49IK00WD. These days, the QRN is very low for quite a long time! The 
>>>> plan is to run about 500W RF power, or more, depending on the voltage 
>>>> limit of the antenna. And the plan is to start transmitting tonite, after 
>>>> the experiment with VO1NA, i.e. i'll come on air arround 2 UTC, hopefully. 
>>>> I will run the test until the late afternoon. First i'm TXing a stable 
>>>> frequency until 9 UTC, 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 stop.
>>>> Will someone give it a try and watch for me?
>>>> 
>>>> 73, Stefan/DK7FC
>>> 
>> 
> 
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