RE: NEC-LIST:nec2 newbie question: Biconical antenna

We may need to be careful with our terminology here. As I see it,
a biconical dipole is a balanced device requiring a balun to convert
the coax mode to one-terminal-pair push-pull. Also, considering a
vertical biconical the maximum gain is realized broadside, normal
to the dipole, i.e. towards the "horizon".

The discone is inherently unbalanced requiring no balun, even though
some coax feedline current/radiation seems inevitable and likely
should be controlled. And, whether the disk is atop or beneath the cone,
the radiation pattern point of maximum gain is a function of disk size (in
wavelength measure) therefore a function of frequency. That is to say,
the maximum gain point of the pattern is elevation-angle dependent.

For these reasons it's better to rely on the full biconical for wideband
measurements while for less-critical and narrower-band base-station
use the simplicity of the discone is attractive and the performance is
usually acceptable.

True balance seems difficult to achieve in any choice.

At 07:50 PM 10/17/2002 -0600, Brent DeWitt wrote:
>Just to add something that I'm sure Davor knows but didn't say:
>
>Biconical dipoles and discones are both broadband dipoles. They both
>broadband a conventional half wave dipole by virtue of a tapered "fat"
>element. Discones are popular at higher frequencies because of the solid
>surface of the elements being better behaved than individual wire elements.
>I don't have it readily available, but there was a good paper in the IEEE
>Transactions on Antennas and Propagation a couple of years back on the
>modeling of a skeletal biconical with NEC. They struggled quite a bit to
>make the model match the real thing (a Rhode & Schwarz if I remember
>correctly). I tried to reproduce their work and found similar problems
>trying to model an EMCO 3108.
>
>Brent
>
>-----Original Message-----
>From: nec-list-admin_at_gweep.ca [mailto:nec-list-admin_at_gweep.ca]On Behalf
>Of Davor Virkes
>Sent: Thursday, October 17, 2002 12:42 AM
>To: nec-list_at_gweep.ca
>Subject: Re: NEC-LIST:nec2 newbie question: Biconical antenna
>
>
>Hi,
>
>>The antenna should be connected to a spectrum analyzer via BNC or
>>N-Connector (50 ohms).
>
>Discones are much better suited for excitation with coax, and are easily
>built. In this configuration, it could be designed as a snap-on, and used
>as a handy reference antenna for signal level measurements eg. for micro
>and pico cells.
>
>Davor
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Dan Bathker

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