On 9 abr, 21:39, "usmcbrat" wrote:
Hi All:

Is there an optimum % length for an antenna when the antenna is a simple
straight stick? 1/4 wave... 1/2, 5/8, full wave? Does it differ depending
on wavelength? If size is not a consideration, is a full wavelength
preferable?

I've Googled around a bit but haven't found a good explanation yet.

Hello,

For a single straight stick (assuming a monopole antenna) and maximum
radiation perpendicular to the stick, a half wave has my preference.
Reason for that: good compromise between gain and requirements for an
RF ground. An electrically end-fed half wave stick has lowest
requirements with respect to ground. Disadvantage is you need a
matching network to match to about 500...3 kOhms (depending in length/
thickness ratio).

A full wave monopole does virtually not radiate perpendicularly to the
stick.

The highest gain over perfect ground gives a 5/8 monopole. In most
situations, ground is not perfect and then it is questionable whether
the 5/8 monopole will outperform the half wave monopole.

When you may feed the stick in the middle, 2*5/8 lambda gives the
highest gain. Note that matching requires inductances. 2*1/4 waves
matches easiest to 50 Ohms cable.

A full wave dipole has high input impedance, but also larger bandwidth
than a half wave dipole. All dipoles require some form of balun when
fed from coaxial cable.

It is difficult/impossible to say what length is optimum for your
particular situation.

Best regards,

Wim
PA3DJS
www.tetech.nl (Dutch)
please remove abc from the address.