Message-ID: <5012E2BB.7010203@iup.uni-heidelberg.de>
Date: Fri, 27 Jul 2012 20:49:31 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: Kites
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Warren,

:-)
That's nice. I searched for a similar video. But the 4guys are not so=20
clever and the wind was rather moderate. At > 4 BFT you have no chance=20
to bring that kite down by hand. It is important just to pull it down=20
into the direction where the wind blows, to minimize the forces.
I'm using a deflection roller out of stainless steel which are used by=20
sailors. These are hold by a big supporting loop:=20
http://www.drachenshop.de/images/e-1012406_3.jpg Anyway it was a hard=20
fight in one of the nights, the field completely in darkness and massive=20
winds becoming stronger and stronger. That was when i've been young...

73, Stefan/DK7FC

Am 27.07.2012 20:31, schrieb Warren Ziegler:
> Stefan,
>     I saw this Youtube video of 4 big guys trying to bring down a kite
> like yours:
> http://www.youtube.com/watch?v=3DK7q34sw4XMo
>
>    I would love to try this but I live in an area densely covered with
> tall trees, and it would be quite a drive to an open area where I
> could launch an antenna (children's playground is not a good place for
> a HV antenna!)
>
> 73 Warren K2ORS
>
>
> On Thu, Jul 26, 2012 at 4:48 PM, Stefan Sch=E4fer
> <Stefan.Schaefer@iup.uni-heidelberg.de>  wrote:
>   =20
>> Hello Warren,
>>
>> Am 26.07.2012 19:39, schrieb Warren Ziegler:
>>
>>     =20
>>> Stefan,
>>>        I imagine that a LF or VLF small vertical is a relatively high=
-Q
>>> circuit, how do you manage to keep the kite vertical in resonance and
>>> matched while the kite bounces around in the wind?
>>>
>>>       =20
>> Most of the time the kite was quite stable, i.e. the angle and so the =
C did
>> not change significantly. The antenna current is stable within a 10% l=
imit.
>> When the wind was poor in some situations, the kite drops to a lower a=
ngle.
>> Then the falling ERP is rather affected by the lower effective height =
than
>> by the changing current. The current (say 1A on 8970 Hz) can easyly dr=
op to
>> 400 mA when the angle changes from 80 deg to 40 deg.
>> One method is to compensate this by turning the variometer from time t=
o time
>> or you can use a working point of the variometer that uses a slightly =
to low
>> L. Then the antenna current does not reduce when the kite falls (in ce=
rtain
>> limits of course). This is the case because the little generator that =
i used
>> (up to 550 W RF power in the best times) can be seen as something like=
 a
>> constant power source. So if the kite falls then slightly, the working=
 point
>> moves to the peak of the resonance curve and the rotation speed is som=
ewhat
>> lowered. It was funny to observe this effect for many hours on the fie=
ld :-)
>> But normally the movement of the wire does not strongly change the ant=
enna
>> current.
>>
>> OK?
>>
>>
>> 73, Stefan/DK7FC
>>
>>     =20
>
>
>   =20