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
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