Radials on a elevated antenna only works if the radials are placed at or near the bottom of the antenna and are arranged at a 45* angle.

Any other angle and you might as well not have any radials at all!

On a 10 -12 meter antenna, these radials would need to be at least 1/4 of a wavelength long - 9 feet and preferably 18 feet long to do any good!

If you coil them up they do not work as intended, but they might help a little.

Forget calling them a ground plane, think of them more like a mirror.

If you shine a beam of light directly at a mirror, the light is 100% reflected back towards the source.

If most of your radiated power is located at the bottom of the antenna and you can reflect that power up and forward - it is going to radiate better then something that is only partially effective.

Anything that you don't reflect is adsorbed into the ground - good for keeping the worms warm at night, but not good for radiating RF..

Only a fool would become a ham and then move into an apartment!

The sad truth is that most people do not understand what being a ham is all about anymore and most people thinks that amateur radio is a right and not a privilege.

Trying to be a ham while living in an apartment building would be like trying to be a Ocean liner captain while living in Oklahoma...

The metal railing is much too small in rf area to be an effective counter poise - sorry but who ever told you this should go back to school and get a real education.

El 01-04-14 19:21, Channel Jumper escribió:
Radials on a elevated antenna only works if the radials are placed at or
near the bottom of the antenna and are arranged at a 45* angle.

Any other angle and you might as well not have any radials at all!

I don't support this reasoning, I see many good antennas that don't
follow this rule.



On a 10 -12 meter antenna, these radials would need to be at least 1/4
of a wavelength long - 9 feet and preferably 18 feet long to do any
good!

If you coil them up they do not work as intended, but they might help a
little.

Forget calling them a ground plane, think of them more like a mirror.

I see the ground provision just as a means to pull out the current
that goes into the radiator (as I don't want to draw this current out
of the braid). If 1 A goes into the radiator, I need to draw 1 A from
my ground/counterpoise/etc. I would like to have the resistance of the
ground provision small with respect to the real part of the radiator's
impedance.


If you shine a beam of light directly at a mirror, the light is 100%
reflected back towards the source.

I think you can't compare the light analogy with a situation where the
wavelength is no long small compared to the structure.

A ground provision can be good enough for a well-designed half-wave
end-fed antenna, but useless for a quarter wave whip. You can't
explain this with light analogy.



If most of your radiated power is located at the bottom of the antenna
and you can reflect that power up and forward - it is going to radiate
better then something that is only partially effective.

Anything that you don't reflect is adsorbed into the ground - good for
keeping the worms warm at night, but not good for radiating RF..

Only a fool would become a ham and then move into an apartment!

Sometimes you don't have another choice and then you need to get the
best out of it.


The sad truth is that most people do not understand what being a ham is
all about anymore and most people thinks that amateur radio is a right
and not a privilege.

Trying to be a ham while living in an apartment building would be like
trying to be a Ocean liner captain while living in Oklahoma...

The metal railing is much too small in rf area to be an effective
counter poise - sorry but who ever told you this should go back to
school and get a real education.

It all depends on the current you need to draw from it, given certain
power. You will certainly not get good radiation efficiency, but this
doesn't say it is useless.

Given the good conditions at the upper end of HF, you can get useful
efficiency from a small antenna.


--
Wim
PA3DJS
Please remove abc first in case of PM

Channel Jumper wrote:

Radials on a elevated antenna only works if the radials are placed at or
near the bottom of the antenna and are arranged at a 45* angle.

Any other angle and you might as well not have any radials at all!

Utter nonsense.

The radials do have to be at or near the bottom but the angle of the radials
mostly determines the antenna impedance.

With the radials at 90 degrees the impedance will be around 40 Ohms and
at 45 degees very close to 50 Ohms.

One can download the demo version of EZNEC and observe the effect of
radial angle for themselves.

On a 10 -12 meter antenna, these radials would need to be at least 1/4
of a wavelength long - 9 feet and preferably 18 feet long to do any
good!

The ideal radial length for ANY ground plane antenna is slightly longer
than 1/4 wavelength, no matter for what frequencey.

If you coil them up they do not work as intended, but they might help a
little.

If you coil them up, you are inductively loading them, shortening the
physical length just like a loaded vertical.

If you make them electrically around 1/4 wavelength, loaded radials will work
just fine.

Ground plane antennas have been made with 4 hamsticks; 1 for the vertical
element and 3 for the radials and they work.

They major drawback to such is the limited bandwidth of loaded antennas.


snip remaining babbling nonsense



--
Jim Pennino

wrote:
Channel Jumper wrote:

Radials on a elevated antenna only works if the radials are placed at or
near the bottom of the antenna and are arranged at a 45* angle.

Any other angle and you might as well not have any radials at all!

Utter nonsense.

The radials do have to be at or near the bottom but the angle of the radials
mostly determines the antenna impedance.

With the radials at 90 degrees the impedance will be around 40 Ohms and
at 45 degees very close to 50 Ohms.

One can download the demo version of EZNEC and observe the effect of
radial angle for themselves.

On a 10 -12 meter antenna, these radials would need to be at least 1/4
of a wavelength long - 9 feet and preferably 18 feet long to do any
good!

The ideal radial length for ANY ground plane antenna is slightly longer
than 1/4 wavelength, no matter for what frequencey.

If you coil them up they do not work as intended, but they might help a
little.

If you coil them up, you are inductively loading them, shortening the
physical length just like a loaded vertical.

If you make them electrically around 1/4 wavelength, loaded radials will work
just fine.

Ground plane antennas have been made with 4 hamsticks; 1 for the vertical
element and 3 for the radials and they work.

They major drawback to such is the limited bandwidth of loaded antennas.


snip remaining babbling nonsense


Slight correction:

At 90 degrees the impedance will be close to 20 Ohms and at 30 degrees
close to 40 Ohms if not very close to the ground.

It would help if you were to specify what band or bands you are interested
in and how hight this balcony is off the ground.



--
Jim Pennino

El 01-04-14 21:33, escribió:
wrote:
Channel wrote:

Radials on a elevated antenna only works if the radials are placed at or
near the bottom of the antenna and are arranged at a 45* angle.

Any other angle and you might as well not have any radials at all!

Utter nonsense.

The radials do have to be at or near the bottom but the angle of the radials
mostly determines the antenna impedance.

With the radials at 90 degrees the impedance will be around 40 Ohms and
at 45 degees very close to 50 Ohms.

One can download the demo version of EZNEC and observe the effect of
radial angle for themselves.

On a 10 -12 meter antenna, these radials would need to be at least 1/4
of a wavelength long - 9 feet and preferably 18 feet long to do any
good!

The ideal radial length for ANY ground plane antenna is slightly longer
than 1/4 wavelength, no matter for what frequencey.

If you coil them up they do not work as intended, but they might help a
little.

If you coil them up, you are inductively loading them, shortening the
physical length just like a loaded vertical.

If you make them electrically around 1/4 wavelength, loaded radials will work
just fine.

Ground plane antennas have been made with 4 hamsticks; 1 for the vertical
element and 3 for the radials and they work.

They major drawback to such is the limited bandwidth of loaded antennas.


snip remaining babbling nonsense


Slight correction:

At 90 degrees the impedance will be close to 20 Ohms and at 30 degrees
close to 40 Ohms if not very close to the ground.

Jim, nice detail! Many reference say 35 Ohms (as they assume an
infinite ground plane), but it is really as low as you stated.

For JOTA oparation we used a 6 elevated radials arrangement at 40 m
band and I had to extend the radiator to get 50 Ohms. Just adding a
tuning capacitor "removed" the inductive component. Now we have the
means to erect a half wave giving sligtly lower main beam elevation,
and we use 3 radials now.


It would help if you were to specify what band or bands you are interested
in and how hight this balcony is off the ground.





--
Wim
PA3DJS
Please remove abc first in case of PM

In message ,
writes



The ideal radial length for ANY ground plane antenna is slightly longer
than 1/4 wavelength, no matter for what frequencey.

Why is this? I would have thought that a 1/4 wave would be best, as it
offers the lowest impedance.








--
Ian

On Wednesday, April 2, 2014 3:04:29 AM UTC-5, Ian Jackson wrote:
I would have thought that a 1/4 wave would be best, as it
offers the lowest impedance.

Doesn't making the radials a bit long and the monopole a bit short raise the feedpoint resistance? Sorta like an OCF dipole?

In message ,
W5DXP writes
On Wednesday, April 2, 2014 3:04:29 AM UTC-5, Ian Jackson wrote:
I would have thought that a 1/4 wave would be best, as it
offers the lowest impedance.

Doesn't making the radials a bit long and the monopole a bit short
raise the feedpoint resistance? Sorta like an OCF dipole?

But won't you have to shorten the antenna a little to maintain
resonance?
--
Ian

Ian Jackson wrote:
In message ,
writes



The ideal radial length for ANY ground plane antenna is slightly longer
than 1/4 wavelength, no matter for what frequencey.

Why is this? I would have thought that a 1/4 wave would be best, as it
offers the lowest impedance.

First you have to define what "best" means.

All antennas are a trade off for impedance, bandwidth, gain and in most
cases physical ability to build the structure.

Changing the radial length will have a small effect on impdedance and resonant
point but changing the radial angle will have a bigger effect on impedance
and a very small effect on resonant point.

I would suggest downloading the demo version of EZNEC and modeling a GP to
see what small changes in various parameters do.



--
Jim Pennino

In message ,
writes
Ian Jackson wrote:
In message ,
writes



The ideal radial length for ANY ground plane antenna is slightly longer
than 1/4 wavelength, no matter for what frequencey.

Why is this? I would have thought that a 1/4 wave would be best, as it
offers the lowest impedance.

First you have to define what "best" means.

Yebbut ........
You've just said "the ideal radial length for ANY ground plane antenna
is slightly longer than 1/4 wavelength, no matter for what frequency". I
assumed that "ideal" = "best".
..
All antennas are a trade off for impedance, bandwidth, gain and in most
cases physical ability to build the structure.

Changing the radial length will have a small effect on impdedance and resonant
point but changing the radial angle will have a bigger effect on impedance
and a very small effect on resonant point.

True - but what's the angle of the radials got to do with their length?

I would suggest downloading the demo version of EZNEC and modeling a GP to
see what small changes in various parameters do.

I had presumed you had already do this (or something similar) in order
to say that slightly longer than a 1/4 wavelength was ideal. However, I
have always assumed that the steeper the angle of the radials, the more
the groundplane becomes like a vertical halfwave dipole - and the lower
becomes the angle of radiation.



--
Ian