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Re: LF: Finbar's Compact 500kHz Vertical

To: <[email protected]cksheep.org>
Subject: Re: LF: Finbar's Compact 500kHz Vertical
From: [email protected]
Date: 16 Jun 2008 23:21 GMT
In-reply-to: <[email protected]>
References: <[email protected]> <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Dear Claudio,

thank You for answering.

I know that the gain of an active antenna will increase by 6 dB average
by doubling its height. I also have an active Antenna installed, but so
far at a height of 4 meters only. Reception of DI2AM is possible at
night, but weaker than on my other antennas.  

But I have also made experiments with a passive T-antenna (originally
used for LF, capacitiy 350 pF) with an 3:1 (voltage) unun at the
feedpoint, which allows to connect a cable (50 to 75 ohms) to the
receiver.

At my qth longwires up to 7 meters high were not sufficient to receive
even DI2AM at night, for instance. But this was and still is possible
when using the T-antenna at a height of 10 meters. At 7 meters reception
of VLF was sufficient, but on this band all transmitters are QRO. 

Therefore I thought that transmitting antennas would not make any
difference for skywave communication.

Your reference to Christof Rohner is good. I know him personally, as he
is also a radio amateur, and will probably meet him at the next Ham
Radio.     

OK?

73 Ha-Jo, DJ1ZB


"Claudio Pozzi" <[email protected]> schrieb:
> On Saturday 14 June 2008 17:56, [email protected] wrote:
> 
> 
> > According to my experiments on untuned (and broadband) receiving aerials
> > for MF SKYWAVE RECEPTION in eastern Bavaria I have got the impression
> > that a (capacitive) MF aerial should be as high as possible (not
> > regarding loop aerials, they may be located close to the ground, for
> > them the loop area only counts).
> >
> 
> If your antenna is an active one, like mini-whip, I agree.
> You can find some info about "height gain" in this paper, page 7:
> SCHWARZBECK MESS - ELEKTRONIK, "Calibration of Vertical Monopole Antennas 
> (9kHz - 30 MHz)"
> I've lost the WEB link but you can find the paper using Google.
> 
> This paper also have some useful  hints about short and active antennas:
> Christof Rohner, "Antenna Basics", Rohde&Schwarz, 1999
> You can find the paper into the Rohde&Schwarz WEB site.
> 
> 73 de Claudio, ik2pii
> 
> -- 
> Claudio Pozzi  -  Happy Linux User  -  http://www.qsl.net/ik2pii
> 
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