Re: NEC-LIST: Antenna factors of bicone antennas

Hi Sara,

You asked for advice on why you got different antenna factors using
the 3 methods described. I cannot give any good answer to that, but
wonder why you do not use the formula:

AF = (2/lambda) * sqrt( pi*Zo / (G R M));

Zo = 120 pi
G = Gain of biconical
R = Receiver input resistance resistance (normally 50)
M = mismatch loss = 1 - |rhoV^2| where rhoV is the voltage
reflection coefficient

This relates the antenna factor to the antenna gain and input
impedance which is more easily computed. We wrote a paper:
"Characteristics of the Wire Biconical Antenna Used for EMC
Measurements" on this topic in IEEE Trans on EMC Aug 1991, Vol 33,
No 3, pp 1991.

We also found that you need to model the feed using separate wires in
parallel rather than joining them together to achieve 1 feed
segment. You then get many impedances which you have to put in parallel
to get the acual impedance.

Regards
Andre Fourie

Tel: Intl + 27 11 4030380
Fax: Intl + 27 11 4030381
Website: http://www.poynting.co.za
email: fourie_at_poynting.co.za
Papermail: Dr APC Fourie, PO Box 318, Wits, 2050, South Africa
Received on Sat Nov 21 1998 - 21:32:33 EST