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.

There's no single "optimum" length; every length has its own
characteristics, and each length is better for some purposes than
others. I suggest that you visit your local library and check out a copy
of the _ARRL Antenna Book_. It'll provide a good basis for learning
about this interesting topic.

Roy Lewallen, W7EL

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.

"usmcbrat" wrote in message
newsX8Lj.19131$4O1.19019@trnddc03...
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.

If you're talking about a vertical whip antenna, you may want to look at a
5/8 wave - but you would need to add a little coil at the bottom to match
impedence to 50-ohms.
I read somewhere that that the pattern of a vertical antenna improves as the
length approaches 5/8-wave.
Picture the pattern like a small balloon full of water sitting on a map -
and as you increase the length of the whip, you press down on the
water-balloon - making its coverage more horizontal - thus covering more
area. Some of the radiation that would have gone up now goes out.
And a dipole with 5/8 wave on each pole would make it more directional as
well.
I don't have references to point you to, just going by memory - which may -
or may not - be intact.

On Apr 9, 7:05 pm, "Hal Rosser" wrote:
"usmcbrat" wrote in message

newsX8Lj.19131$4O1.19019@trnddc03... 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.

If you're talking about a vertical whip antenna, you may want to look at a
5/8 wave - but you would need to add a little coil at the bottom to match
impedence to 50-ohms.
I read somewhere that that the pattern of a vertical antenna improves as the
length approaches 5/8-wave.
Picture the pattern like a small balloon full of water sitting on a map -
and as you increase the length of the whip, you press down on the
water-balloon - making its coverage more horizontal - thus covering more
area. Some of the radiation that would have gone up now goes out.
And a dipole with 5/8 wave on each pole would make it more directional as
well.
I don't have references to point you to, just going by memory - which may -
or may not - be intact.

..64 wave is the length that gives the maximum gain for a single
element. But.. Single 5/8 elements really need a lower 5/8 element
to live up to expectations. Also, some may prefer slightly shorter
to minimize radiation at the higher angles.
If you had an EDZ, the best length for maximum broadside gain
is .64 wave per leg/pole.
But like Roy says, there is really no best element length unless
you have a specific purpose for the pattern a particular length
provides. Any gain is one direction is a loss in some other direction.
IE: the EDZ will have more gain broadside than a 1/2 wave dipole,
but less gain in the appx end fire directions. No free lunches.. :/

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.

"Wimpie" wrote in message
news:039e23b4-c246-4535-826d-
It is difficult/impossible to say what length is optimum for your
particular situation.

Thanks for all of your info. I don't have a particular situation in mind,
this was just a question for my own education. I didn't know if there was
any advantage to having a "larger" antenna beyond any particular point...
such as a two wavelength or a ten wavelength or a thousand wavelength.