I'm confused about the requirements for a counterpoise for an end-fed wire antenna. I understand
that it's needed, but I don't understand what the requirements are.

Can a ground stake at the base of the feed point serve as a counterpoise, or does it need to be
another wire running under the ground below the antenna?

If a wire is required, how long does the counterpoise have to be?

Would it be better to use insulated or uninsulated wire for a buried counterpoise?

KJ4NTS wrote:
I'm confused about the requirements for a counterpoise for an end-fed wire antenna. I understand
that it's needed, but I don't understand what the requirements are.

If you get 100 replies, you'll probably get 110 different answers to that.


Can a ground stake at the base of the feed point serve as a counterpoise, or does it need to be
another wire running under the ground below the antenna?

No, it makes a good DC ground for lightening protection. A counterpoise can be
run almost anywhere, and the more the better.

If a wire is required, how long does the counterpoise have to be?

..28 wavelength is something I have read, while most people use 1/4 wavelength,
or an electrical equivalent (shorter due to velocity factor).

Would it be better to use insulated or uninsulated wire for a buried counterpoise?

Uninsulated.

Not that some antennas don't need a counterpoise, for example a 5/8th wave
antenna or an end fed zepp which uses no or a very short counterpoise.

A friend of mine has a commercial antenna, which consists of a matching
network, a trap and around 40 feet of wire. It covers 10,20 and 40 meters
with no counterpoise. The matching network can only handle 25 watts,

My speculation is that it's sort of a 5/8th wave type antenna with
loading coils to eletrically lengthen it.

It could also be a 50 ohm 25 watt resistor with a long tail on the "hot" end,
but I really doubt it.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

On Sun, 2 Aug 2009 17:30:31 GMT, "KJ4NTS" wrote:

I'm confused about the requirements for a counterpoise for an end-fed wire antenna. I understand
that it's needed, but I don't understand what the requirements are.

Hi OM,

What are YOUR requirements? (What bands, how long is it?)

Can a ground stake at the base of the feed point serve as a counterpoise, or does it need to be
another wire running under the ground below the antenna?

Both, and more wire(s).

If a wire is required, how long does the counterpoise have to be?

For single band operation? (You aren't very clear about this.) The
deeper into the ground (and deeper than 6 inches doesn't count for
much), the less resonant it will become. Make it as long as your wire
overhead - maybe less.

Would it be better to use insulated or uninsulated wire for a buried counterpoise?

Doesn't matter.

73's
Richard Clark, KB7QHC

On Aug 2, 12:30*pm, "KJ4NTS" wrote:
I'm confused about the requirements for a counterpoise for an end-fed wire antenna. *I understand
that it's needed, but I don't understand what the requirements are.

Can a ground stake at the base of the feed point serve as a counterpoise, or does it need to be
another wire running under the ground below the antenna?

If a wire is required, how long does the counterpoise have to be?

Would it be better to use insulated or uninsulated wire for a buried counterpoise?

With regard to whether you need a counterpoise or not. If your
antenna has two wires at the open end (feed point) then they both must
be connected to the transmitter where there is also an additional
provision for a ground connection ( a must in all cases as the chassis
is floating).If the radiator has only one termination then only one
transmission wire can be connected to it leaving the other wire to be
connected to a ground system which in effect balances your radiator
with a load that does not radiate unless it is the form of a
counterpoise. The effectiveness of your ground system can be measured
by its effectiveness in supplying a resistive feed impedance somewhat
near 30 ohms (above 20 ohms) or so where your transmitter does not
encounter any problems, a counterpoise will present a higher
impedance. An end fed antenna cannot be of a fractional wavelength and
thus the ground field or counterpoise is required to be added to
provide an impedance that can be fed by the transmitter without a
problem so you can enjoy useage of your antenna

"Art Unwin" wrote in message
...
On Aug 2, 12:30 pm, "KJ4NTS" wrote:

ART IS BACK!

don't believe a thing he says, even if you think it kind of makes sense,
which it doesn't.

On Aug 2, 12:30�pm, "KJ4NTS" wrote:
I'm confused about the requirements for a counterpoise for an end-fed wire antenna. �I understand
that it's needed, but I don't understand what the requirements are.

Can a ground stake at the base of the feed point serve as a counterpoise, or does it need to be
another wire running under the ground below the antenna?

If a wire is required, how long does the counterpoise have to be?

Would it be better to use insulated or uninsulated wire for a buried counterpoise?

An end fed wire antenna should be very close to a half wave in length
for the intended frequency. If coax fed, the objective is to make the
antenna look as balanced as possible by insuring that the current in
the counterpoise and the radiating element are very nearly equal. A
half wave end fed is a high voltage low current antenna, and
everything around the antenna will affect its impedance and balance,
obviously the counterpoise will have a large effect.

If the end fed antenna (half wave) is not in the clear, then the
counterpoise is cut-and-try. If in the clear, antenna modelling will
provide useful results, see W8JI web pages. A counterpoise is needed,
but without knowing your exact situation, cut-and-try is your best
bet.

Gary N4AST

On Aug 2, 3:01*pm, Art Unwin wrote:

An end fed antenna cannot be of a fractional wavelength...
_________________

? ?

Art, note that the vertical monopoles used by MW broadcast stations
are ALL fractional-wavelength radiators, and probably 99% of them are
end fed.

On 2 ago, 19:30, "KJ4NTS" wrote:
I'm confused about the requirements for a counterpoise for an end-fed wire antenna. *I understand
that it's needed, but I don't understand what the requirements are.

Can a ground stake at the base of the feed point serve as a counterpoise, or does it need to be
another wire running under the ground below the antenna?

If a wire is required, how long does the counterpoise have to be?

Would it be better to use insulated or uninsulated wire for a buried counterpoise?

Hello,

As you might know, the current that goes into the end-fed antenna
equals the current that goes into the counterpoise.

The requirement for a good, efficient counterpoise is that it should
not dissipate the RF power and that (preference) the impedance is far
below the feed point impedance of the end-fed antenna.

The requirement last mentioned is for assuring that you can feed your
antenna with an unbalanced feeder (coaxial cable). It also helps to
avoid that when you touch a coaxial connector while transmitting, you
don't burn your fingers.

Half or full wave resonant antennas have high input impedance (kOhm
range), hence requirements for counterpoise are easy to meet. It is
easy to create a counterpoise impedance of several hundreds Ohms.

For a quarter wave (or shorter antenna), the resonant impedance is in
the 30 Ohms range or below (for short antennas). In that case it may
be very difficult to get counterpoise impedance far below 30 Ohms.

As Geoffrey mentioned, with 100 replies, you will have 100 different
answers. There are many ways to make a counterpoise; all have their
advantages (and disadvantages).

Generally spoken, the more metal the better. However at a certain
point, doubling the amount/length of metal will not give significant
increase. When you add more metal and the antenna impedance at
resonance doesn't change, adding more metal is not necessary.

In my opinion, many short wires are better then one long wire. When
you have good ground conductivity, driving rods deep into the ground
is not necessary (skin depth issue). In case of single frequency band
operation, you might consider 2 or 3 elevated quarter wave resonating
counterpoise wires.

I know this is not a direct answer to your question, but I hope it
will bring you closer to an answer.

Best regards,

Wim
PA3DJS
www.tetech.nl
please remove the obvious character combination in case of PM.

On Aug 3, 5:24*am, Richard Fry wrote:
On Aug 2, 3:01*pm, Art Unwin wrote:

An end fed antenna cannot be of a fractional wavelength...

_________________

? ?

Art, note that the vertical monopoles used by MW broadcast stations
are ALL fractional-wavelength radiators, and probably 99% of them are
end fed.

I regard a radiator with a counterpoise as being center fed of a
given impedance to connect to regardles whether the counterpoise is
above ground or not. If a radiator is of a closed cuircuit form it may
be fed at any point in physical terms. Other peoples definitions may
vary. The poster I understood to be at the position of the end of a
transmission line with two wires in hand and wanted advice from that
point to procede. If his advisers are going to quibble then he needs
to go elsewhere for advise or settle for a poll.

"KJ4NTS" wrote in message
...
I'm confused about the requirements for a counterpoise for an end-fed wire
antenna. I understand
that it's needed, but I don't understand what the requirements are.

Can a ground stake at the base of the feed point serve as a counterpoise,
or does it need to be
another wire running under the ground below the antenna?

If a wire is required, how long does the counterpoise have to be?

Would it be better to use insulated or uninsulated wire for a buried
counterpoise?

All these questions depend on your particular situation. In a typical
antenna installation you would first seek to follow the instructions for
that antenna. Especially if you don't understand the physics involved. You
will probably already have some sort of ground through the power supply.
Any better ground than that must actually be better to whatever energy you
are trying to "ground".

Someone mentioned RF in the shack and being bit from the chassis or
connector shell. The best way to avoid that is for the energy at the coax
connector to see 50 ohms, and for the radiating portion of the antenna to be
well out of the shack. In that case, you don't need an RF ground on the
radio.

A ground stake at the feed point along with a remote tuner should be
sufficient if you have really low resistance soil. You will probably
benefit by adding a counterpoise and you will probably never have a perfect
ground. It is better to have uninsulated wire because it will conduct into
the ground. Some think insulated is better because it will last longer for
a little expense in performance.

A remote tuner (or matched antenna) at the feed point, will keep the RF to
the transmission line and prevent high voltages on the line and keep losses
to the minimum.