NEC-LIST:Information needed about an antenna design

Dear Sir,

We need to use an antenna in a course project that operates at
144Mhz with a bandwidth of 14Mhz (from 137Mhz to 151Mhz). We
also want it to be directional and 50ohm matched when a big
metal plate is placed two inches away. Could you tell me whether
it is feasible to use a folded-dipole to achieve our goal? or
where I can find corresponding information so that I can design
such an antenna in a short time?

We use 300ohm twin-lead wire for our antenna and the simulation
results shows that the antenna resistance drops to about 10ohm
when it is 2'' away from the big metal plate. We use four-time
folded dipole to bring the resistance back to 50ohm again. Now
the problem is that the bandwidth is only 5Mhz to 7Mhz instead
of 14Mhz. It is suggested by some textbook that the bandwidth
may be increased by increasing the diameter of dipole, but I
am just wondering whether there is any other way to do it just
using our current 300ohm twin-lead wires.

Your information would be greatly appreciated!

Sincerely,

Jim

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