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Message-ID: <001d01cad190$aa92e590$0901a8c0@lark>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <o2kfc7eccec1004010402n7f00e1c3l8b88ea090c0fb8bb@mail.gmail.com>
Date: Thu, 1 Apr 2010 12:44:15 +0100
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Subject: LF: Re: E-Field Probe calibration question
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Hi Andy maybe I dont read it right, but if that is an E-field probe it is
not a "dipole" The input capacitance senses the voltage at two points on the
wavefront. The ground plane is, I believe, irrelevant. You just need another
capacitance separated from the "probe" to reference to voltage to. See
Renato's balanced probe (www.vlf.it)  In your case this is the car.....but
it could be the size of a dinky toy.The area of the wavefront intercepted by
the probe or the ground reference does not affect the terminal
voltage.....as I see it.................of course I might just be wrong cos
i am really a scientist not an enjuneir!!
 :-))
Alan

----- Original Message ----- 
From: "Andy Talbot" <andy.g4jnt@googlemail.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Thursday, April 01, 2010 12:02 PM
Subject: LF: E-Field Probe calibration question


> I have a calibrated E Field antenna (Procomm AAC-1) with a quoted
> antenna-factor of 0.15V into 50 ohms when placed in a field of 1V/m,
>
> This is mounted in the centre of a car roof and fed via a bulkhead
connector
> to a calibrated measuring receiver inside the vehicle, which we can assume
> is a Faraday cage at LF,  S0 my question is :    How is the effective
height
> of the antenna changed?    It was 0.15m - the specification said so - but
> this would have been over an infinite groundplane.  Do I regard the body
of
> the car as being the other half of a dipole?  In which case, at 1.5m it
adds
> 20dB to the received signal and makes a mockery of calibrated measurement
of
> the E-Field value..
>
> Is it worth persuing this route, or better to stick to untuned loops for
> calibrated E-Field measurements at LF/MF?
>
>
> Andy
> www.g4jnt.com
>