Message-ID: <4BAD19D0.300@telia.com>
Date: Fri, 26 Mar 2010 21:32:16 +0100
From: "Johan H. Bodin" <jh.bodin@telia.com>
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Subject: Re: LF: Question about ground impedance at 8.97 KHZ  Stefan.
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Hi Paul,

it sounds like your impedance bridge is measuring the absolute impedance
(that is Z = (R^2 + X^2)^0.5 where R is the real part, resistance, and X
is the imaginary part, reactance). R is probably a 10 to a few hundred
ohms, most of it is ground resistance - it can be neglected - the major
part of your impedance is the capacitive reactance of the antenna (Xc).
At 9 kHz, where C = 1/(2*Pi*9000*Xc), 70 kOhms means 253pF which is in
the ballpark for your 170' wire (about 5pF/m).

73
Johan SM6LKM

----

Paul A. Cianciolo wrote:
> 
> Hello All,
> 
> Below is a quote from the Stefan's web page concerning his latest "Dreamers Band" DX contact Congratulations again Stefan.
>>From this information alone is it possible to calculate or know the antenna system impedance.
> 
> 
> 
> 
> "100m Vertical wire antenna, coil/antenna voltage was abt 15kV rms, average antenna current about 480mA, giving up to 1,7mW ERP. Applied power was up to 250W."
> 
> Pertaining to the coil "Technical and mechanical data: L=553mH, Q=82, R(DC)=283 Ohm; 0,4mm diameter enameled copper wire, about 1200 turns! Average diameter 0,55m, height abt 0,5m. So, about 2000m wire! :-)"
> 
> 
> 
> I have built a small impedance bridge that operates at 10 KHZ and shows my sloping 170' wire as 70K Ohms. I can also see approx 500 PF that can be nulled out using the bridge?
> 
> Can the 70K value possibly be correct?   (3) 6' ground rods about 6' apart are the ground... plus the electrical ground of the house.
> 
> I am hoping to attempt a local transmission on 9KHZ 
> 
> Any information would be helpful.
> 
> Thank you
> 
> Paul
> 
> W1VLF
> 
> 
> 
> 
>