I have an attic vertical with four 1/4 wave wires extending in 4 different directions horizontally from the shield of the feed coax at the base of the vertical element. I have heard that there is a difference in a radial and a counterpoise. Which are these functioning as? Thank you for any help you can give me.
Jim
W4NTA
- w4nta asked 7 months ago
- last edited 7 months ago
- You must login to post comments
Because the antenna is far from the Earth (no capacitive coupling to the Earth) and because the “radials” are resonate, I would argue that the horizontal wires in the attic are elevated radials. See reference.
That said, one might argue that the horizontal wires are capacitively coupled to the house underneath the radials. That might be true, but they are probably also capacitively coupled to the roof. Since such installations are messy, I would not be tempted to argue about conceptual terms like ground, counterpoise and radial. The wires are set up to be elevated radials, whether or not they function well in that role.
Andy
- wa3ltj answered 7 months ago
- You must login to post comments
Hi Jim. Happy to have this question be offered up for Elmer response because it is a question without a good answer. As long as I have operated, there have been divergent views on which does what. The common wisdom is that radials and counterpoises are both essential parts of an antenna system, helping to create an effective ground plane, but they are used in slightly different ways. Radials are typically long wires laid out horizontally on or just below the ground and are often used with vertical antennas. Imagine an umbrella with its ribs spreading out from the center—radials work similarly, providing a low-resistance path for the radio frequency (RF) currents. This ensures that more power is radiated effectively, rather than being lost in the ground. You might see radials used in large open spaces where there’s plenty of room to spread out these wires evenly around the base of the antenna.
On the other hand, counterpoises are used when installing radials on or near the ground isn’t practical, like on rooftops or in an attic. Instead of lying on the ground, counterpoises are elevated networks of wires or metal surfaces suspended above the ground. Think of a counterpoise as a horizontal wire mesh or a series of wires forming a flat surface positioned below the antenna but above the ground. This setup still provides the necessary low-impedance path for RF currents but is more versatile in spaces where ground radials can’t be used.
The primary difference lies in their installation and application. Radials need more wires and are spread out symmetrically around the antenna on or just under the ground, making them ideal for outdoor areas with plenty of space. Counterpoises, however, can be smaller and fewer in number, and because they are elevated, they fit well in restricted spaces like rooftops or attics.
In your attic setup, if you have wires spread out symmetrically around the antenna, they are likely acting as radials, even though they are elevated, which is less common but possible in constrained environments. If these wires form a network that acts as an artificial ground plane and are suspended in the attic, they might be serving as a counterpoise. Both methods aim to improve your antenna’s performance by ensuring a proper return path for RF currents, but the choice between radials and counterpoises depends on your specific installation environment and space availability.
In short dear Jim, in either case, what you are fundamentally acting as a return path for the RF or, as I like to say, they are completing the wave.
Other Elmers welcome to weigh in!
Jim | K3MRI
- Jim answered 7 months ago
- last edited 7 months ago
- According to my 1958 ARRL Amateur Radio Handbook, short answer, radials. To remove any controversy, let’s agree to “wires”. Hi.
- You must login to post comments
Jim (K3MRI),
Thank you for your extensive and informative reply to my question. I believe I have a better idea as to the difference between radial(s) and a counterpoise. However, I’m still not clear as to which I have in my attic. You write that:
“if you have wires spread out symmetrically around the antenna, they are likely acting as radials, even though they are elevated”.
I assume that 4 1/4 wave wires connected to the coax shield at the base of the vertical, running in 4 equidistant directions along the attic floor are considered “spread out symmetrically” and “elevated” since they are 20 or more feet from earth ground. Am I correct here?
You also write that:
“If these wires form a network that acts as an artificial ground plane and are suspended in the attic, they might be serving as a counterpoise.”
I am confused since I always envisioned a “ground plane” antenna as one that frequently has four wires (metal elements) connected along with the coax to the feed point (base) of a vertical element. So does that make them radials or a counterpoise or both?
I also do not understand what you mean by “form a network”. Can you elaborate on this?
If I’m beating a dead horse, or any further answers would not contribute to my goal to maximize the efficiency of my attic vertical, please just ignore them, and accept my gratitude for the time you’ve already so graciously afforded me.
73,
Jim
W4NTA
- w4nta answered 7 months ago
- You must login to post comments
Andy,
Thank you for the additional information and reference to the PDF.
I will look forward to reading it.
In the mean time, I’ll attach the 4 radials/and/or/counterpoises to the base of the vertical and test it.
My original purpose in constructing the vertical was to achieve a lower takeoff angle than the 40m dipole, also in the attic, so as to work longer distance DX.
73,
Jim
W4NTA
- w4nta answered 7 months ago
- Perhaps you can use WSPR to compare the two antennas. There is actually special hardware and software for this, but you might be able to get some idea with less formal testing.
- You must login to post comments
Please login first to submit.