Regarding antennas, what does counterpoise mean?

[W5LZ]

I'm afraid that old antenna pictured isn't a horizontally polarized antenna, it's a vertical... with a 'top hat' (cap-hat). Howz that for a 'money-wrench'??
- 'Doc

 

[Road Squawker]

"The antenna is of the multiple tuned type with two tuning points and is strung between two towers, 150 ft. in height and 250 ft. apart. Beneath the antenna is the counterpoise consisting of twelve wires parallel to the antenna, 15 ft. above the ground

a classic NVIS design with verticle polarization

 

[HomerBB]

Ya'll beat me to it.

 

[HomerBB]

Ya'll beat me to it.

I had looked at this on the job on my Iphone and could not verify my impression that we were looking at an NVIS setup, so by the time I got back to the thread others had addressed it.

 

[The DB]

I'm afraid that old antenna pictured isn't a horizontally polarized antenna, it's a vertical... with a 'top hat' (cap-hat). Howz that for a 'money-wrench'??
- 'Doc

Looking at the KGO picture again, I suppose I could see it that way. I wish we had more to go on than a picture and a short description.


The DB

 

[HomerBB]

I'm afraid that old antenna pictured isn't a horizontally polarized antenna, it's a vertical... with a 'top hat' (cap-hat). Howz that for a 'money-wrench'??
- 'Doc

Yeah, you may be right about that one. It looks to be there . . .

 

[Marconi]

The Eznec model I made of the image "Classic Counterpoise" is a 1/4 wave vertical. It has a vertical 1/8 wave with a 1/8 wave top hat, and when I extend the top hat vertically to make the radiator fully a 1/4 wave, the pattern looks very similar with a little gain and lowering the angle.

So IMO these old antenna images are showing us vertical 1/4 wave antennas at about 800 khz am, like 'Doc said and Homer and DB agree.

DB, there is enough info in the text of the image to figure this out.

 

[HomerBB]

Makes sense.
In your models are the counterpoise connected to ground (braid), or simply beneath it without mechanical connection. From the diagram you used it appears they obtained a match from the inductor/capacitor matching device and the counterpoise was simply floating beneath as I understand it should be.

 

[Marconi]

Makes sense.
In your models are the counterpoise connected to ground (braid), or simply beneath it without mechanical connection. From the diagram you used it appears they obtained a match from the inductor/capacitor matching device and the counterpoise was simply floating beneath as I understand it should be.

Homer, I know very little about how a counterpoise is supposed to connect and work, but I attached my 3 radials directly to the bottom of the vertical 1/8 wave radiator, which is 4" above the ground (Earth). So neither is directly connected to the dirt. This may be a distinctive part of the idea for the counterpoise...that it not directly touch the ground.

I think the counterpoise needs to be attached to the antenna, just not directly attached to the Earth.

 

[Marconi]

Here is the image again, and it shows the counterpoise wires are connected to the bottom of the radiator and isolated from the ground.

The model shows a very low resistance at 19.52 ohms and a +5 ohms reactance for the dimensions I used. So, this shows about 2.6 SWR, and it probably needs a little matching.

 

[hookedon6]

they may be isolated @ D.C. , but @ RF they are not

 

[hookedon6]

seems that there is some confusion about the difference between a MARCONI antenna and a HERTZ antenna.

Nearly all antennas have been developed from two basic types, the Hertz and the Marconi. The basic Hertz antenna is 1/2 wavelength long at the operating frequency and is insulated from ground. It is often called a DIPOLE or a DOUBLET. The basic Marconi antenna is 1/4 wavelength long and is either grounded at one end or connected to a network of wires called a COUNTERPOISE. The ground or counterpoise provides the equivalent of an additional 1/4 wavelength, which is required for the antenna to resonate

 

[HomerBB]

seems that there is some confusion about the difference between a MARCONI antenna and a HERTZ antenna.

Nearly all antennas have been developed from two basic types, the Hertz and the Marconi. The basic Hertz antenna is 1/2 wavelength long at the operating frequency and is insulated from ground. It is often called a DIPOLE or a DOUBLET. The basic Marconi antenna is 1/4 wavelength long and is either grounded at one end or connected to a network of wires called a COUNTERPOISE. The ground or counterpoise provides the equivalent of an additional 1/4 wavelength, which is required for the antenna to resonate

Glad you brought it up. Of course, this antenna type thing could enter the thread and add tangential confusion, so it is good we get a chance to speak to it as we move forward in the thread.

- Counterpoise

"With respect to systems using vertical monopoles, the confusion or conflation is now complete. At one time, the notion of a counterpoise distinguished a certain kind of ground system from the typical system of buried radials. The counterpoise consisted of radials (ideally) or other shapes (practically in restricted spaces) insulated from the ground and placed relatively close to ground as measured in terms of wavelengths. The theory of the counterpoise involved creating sufficient capacity between the ground radial system and the ground itself to increase the efficiency of the monopole system, and as reported by Laport and others, it yielded higher efficiencies in some cases than buried radials.

One consequence of the engineering use of the term counterpoise was a 3-part distinction. Below the ground, we have buried radial systems with the wire in direct (or nearly direct, if the wires are insulated) contact with the ground. Next, we have the counterpoise alternative to buried radials. The counterpoise size and wire density equaled that of the buried radial system for maximum efficiency. Third, we have elevated radials, where the capacitance between the radials and the ground is too small to be effective in the determination of antenna efficiency. Rather, the radials become part of the antenna structure sufficiently independent of the ground that antenna resonance is a function of the overall antenna size at the operating frequency. Under these conditions, of course, the required element and radial lengths will change according not only to antenna height, but as well with the number of radials used and whether we leave the tips open like spokes or connect them together with a perimeter wire. The general properties of elevated radials apply regardless of the height of the antenna above ground once we pass through the frontier between the counterpoise and genuinely elevated radials.
Unfortunately, current literature available to radio amateurs blurs the distinction among these three relatively distinct cases, only one of which corresponded to the traditional engineering use of the term. If the term now covers every type of antenna with radials, then we may completely drop the term and simply say that an antenna needs radials to work. Or we might even resurrect the term "Marconi" antenna, although that option might itself create more confusions than it resolves."

Only maintaining clarification of the makeup. And being sure we do not digress from the effort made so far to place the distinctions where they belong with respect to the subject of the counterpoise vs vulgarizations of the term. It's not a discussion on the subject of Marconi v Hertz antennas, but of the nature of the radial network once known as the counterpoise.

Thanks for the answer, Marconi, not to be confused with Hertz. :tongue:

 

[The DB]

A marconi antenna is a quarter wave vertical antenna over either real ground or an artificial ground plane. The artificial ground plane being called a "counterpoise" by some people is a recent development based on what I believe is a common misunderstanding of the term. Cebik has an article that describes what I am saying perfectly called Counterpoise? On the Use and Abuse of a Word. It is a good read that I suggest everyone that uses the term at hand to read it at least once.

Wow, bringing up hertz and marconi antennas... Even most older books on antenna theory don't include those names for antenna types.


The DB

 

[The DB]

Ha, Homer got there first as I typed something up, thought I hit the submit button and apparently missed it...


The DB