What is the nature of free space such that it requires antennae to be at
least 1/4 wave
before accepting radiation efficiently?

Is it that some form of electric "twist" must be appled to Free Space, and
that
the maximum "twist" occurs with 1/4 cycle of a quarter wave?

Were there to be two short antennae closely spaced, but fed 90 degrees
out of phase, wouldthat result in efficient radiation?

What if they were spaced by 1/4 wave but with the feeders completely
screened
from Free Space, or does there have to be all fractions of antnna betwen the
two extremes?

"gareth" wrote in message
...
What is the nature of free space such that it requires antennae to be at
least 1/4 wave before accepting radiation efficiently?

Is it that some form of electric "twist" must be appled to Free Space, and
that the maximum "twist" occurs with 1/4 cycle of a quarter wave?

Were there to be two short antennae closely spaced, but fed 90 degrees
out of phase, would that result in efficient radiation?

What if they were spaced by 1/4 wave but with the feeders completely
screened
from Free Space, or does there have to be all fractions of antnna betwen
the two extremes?


Why not build a model on, say, 70cm and find out for yourself?
--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.uk

On Thursday, September 10, 2015 at 5:27:41 AM UTC-5, gareth wrote:
What is the nature of free space such that it requires antennae to be at
least 1/4 wave
before accepting radiation efficiently?

Ding, ding, ding. Totally false statement.
Don't pass go, don't collect $200.

wrote in message
...
On Thursday, September 10, 2015 at 5:27:41 AM UTC-5, gareth wrote:
What is the nature of free space such that it requires antennae to be at
least 1/4 wave
before accepting radiation efficiently?

Ding, ding, ding. Totally false statement.
Don't pass go, don't collect $200.

Convince yourself by calculating the retarded potential from a far field
when
the same field strength comes from a dipole and when it comes from a short
antenna.
You find that there has to be more power fed into the short antenna
(irrespective of
feed impedances and ohmic resistances) to achieve that same field strength.

"gareth" wrote in message ...

wrote in message
...
On Thursday, September 10, 2015 at 5:27:41 AM UTC-5, gareth wrote:
What is the nature of free space such that it requires antennae to be at
least 1/4 wave
before accepting radiation efficiently?

Ding, ding, ding. Totally false statement.
Don't pass go, don't collect $200.

# Convince yourself by calculating the retarded potential from a far field
# when
# the same field strength comes from a dipole and when it comes from a short
# antenna.
#You find that there has to be more power fed into the short antenna
# (irrespective of
# feed impedances and ohmic resistances) to achieve that same field
strength.

Well, I don't know what you are calling "retarded potential".

At any rate, if the radiated power is equal for two different antennas, why
would the field strength be different, except as related to pattern
differences?

"Wayne" wrote in message
...

Well, I don't know what you are calling "retarded potential".

It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.

It is termed, "retarded" because the radiation originated at some time in
the past.

"gareth" wrote in message ...

"Wayne" wrote in message
...

Well, I don't know what you are calling "retarded potential".

It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.

It is termed, "retarded" because the radiation originated at some time in
the past.

OK now I know. I hadn't heard the term before.

But, how about my question?

" if the radiated power is equal for two different antennas, why
would the field strength be different, except as related to pattern
differences?"

The radiated power just is spread out differently.

On Thursday, September 10, 2015 at 6:06:33 PM UTC-5, gareth wrote:
wrote in message
...
On Thursday, September 10, 2015 at 5:27:41 AM UTC-5, gareth wrote:
What is the nature of free space such that it requires antennae to be at
least 1/4 wave
before accepting radiation efficiently?

Ding, ding, ding. Totally false statement.
Don't pass go, don't collect $200.

Convince yourself by calculating the retarded potential from a far field
when
the same field strength comes from a dipole and when it comes from a short
antenna.
You find that there has to be more power fed into the short antenna
(irrespective of
feed impedances and ohmic resistances) to achieve that same field strength.

To put it plainly in a language you can likely understand, bull****!

If you feed a 1/2 wave dipole with 100 watts, almost all of that power
will be radiated by the antenna.

If you feed a 1/10 wave dipole with 100 watts, almost all of that power
will be radiated by the antenna.
Any difference between the two would be so small as likely to be hard to
measure. This is etched in stone theory known for many years.

In rec.radio.amateur.antenna gareth wrote:
What is the nature of free space such that it requires antennae to be at
least 1/4 wave
before accepting radiation efficiently?

The entrinsic impedance of free space.

snip remaining ignorant babble


--
Jim Pennino

"Brian Morrison" wrote in message
...
On Thu, 10 Sep 2015 11:27:38 +0100
gareth wrote:

What is the nature of free space such that it requires antennae to be
at least 1/4 wave
before accepting radiation efficiently?

There is no requirement of this nature, the only reason for relatively
large antennas is to achieve an input impedance that makes power
transfer into the antenna relatively efficient.

That is a side issue of the phenomenon