Re: NEC-LIST: Fw: Lambda/4 monopoles lamdba/4 apart

At 10:58 AM 9/22/2003 -0700, Chuck Counselman wrote:

>Feed the monopoles with equal-magnitude, quadrature-phased, currents by
>
>(1) deleting those voltage sources;
>
>(2) connecting a transmission line (use the TL command) from the fed
>segment (second from the bottom) of each monopole to the same, one, new,
>very short (0.001 wl or less) segment, located anywhere that's legal;
>
>(3) giving these two transmission lines equal characteristic impedances
>(Zo = 1 ohm will do), and making both their electrical lengths equal to 90
>degrees at the operating frequency; and
>
>(4) putting a source (a voltage source will do) in the aforementioned,
>new, very short segment (to which both TL's) connect.
>
>You will get a more nearly perfect cardioid pattern if you make the
>monopole wires thinner.
>
>-Chuck, W1HIS

Or, use an NT card to connect the two little segments, which makes it
frequency independent (unlike the TLs).

4nec2 does this automatically, as do some other well known NEC implementations.

Something like this:
CM Pair of 40 meter 1/4 wave verticals
CE
GW 100 20 9.14 0 0 9.14 0 10.0 .01
GW 200 20 -9.14 0 0 -9.14 0 10.0 .01
GW 9901 1 -0.001 0.0 9901.0 0.001 0.0 9901.0 0.001
GW 9902 1 -0.001 0.0 9902.0 0.001 0.0 9902.0 0.001
GE 1
EK
GN 1
EX 0 9901 1 0 0.0 1.0 0.0 0.0
EX 0 9902 1 0 1.0 0.0 0.0 0.0
NT 9901 1 100 1 0.0 0.0 0.0 1.0
NT 9902 1 200 1 0.0 0.0 0.0 1.0
XQ

James Lux, P.E.
Spacecraft Telecommunications Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875

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