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" <[email protected]>
To: <[email protected]>
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
