The only critical length of a dipole is the end-to-end length. The length
of the loading coil when inserted in the antenna should not affect this.

Locate the centre of the loading coil at the point where it is supposed to
be along the antenna and reduce the lengths of the antenna elements on
either side of it by half of the length of the coil.

In other words, the total reduction in length of the antenna elements is
equal to the coil length, leaving the original dipole end-to-end length
unchanged.
----
Reg, G4FGQ

===================================

"George" wrote in message
link.net...
I have a question that's probably easy for anyone with practical
experience
building UHF antennas. I need to make a shortened dipole (from tubing) at
450 MHz without sacrificing too much gain compared to full-size.

I have a design based on EZNEC. Total shortened "half-wave" dipole length
is 0.32 lambda. Half of that of course is in each of the two elements.
There is a loading coil in the middle of each element. EZNEC assumes zero
length, non-radiating coils. In reality, the coil length is significant
compared to the element length.

So, how do I build this thing considering the real coil length? Can the
coil be inserted in the middle of each element without reducing the
element
length by the length of the coil? In other words, would final element
length be 0.32 lambda plus coil length? Or, should the elements be
shortened to maintain overall 0.32 lambda end-to-end length?

Thanks.

George K6GW