I used antennas of the EH type and made them structurally for bands from 80m to 6m.
They have their design limitations and they have their pain points and there are also problems with the strong EM field near the antenna.
Structurally, they have proven to be the best for the greater stability and VF properties of the polyethylene pipe, polypropylene. I also tried PVC waste pipes, but with outputs of around 100W, problems arose from HV/VF conductivity of the filling in these PVC plastic pipes.
PPR water pipes have better VF properties.
However, they are harder and less strong.
They can be purchased in diameters up to 125 mm directly from the warehouse in a length of 4 m, for example, in BA at the company empiria.
For example, the EH antenna for the 80m band with a pipe diameter of 75mm worked for me.
The length of the EH dipole is 2 x 80 cm thanks to the construction material Al sheet.
I rolled the sheet to a slightly smaller diameter on a rolling machine ( in tinsmithing)
Galvanized Fe sheet can also be used, the difference is only in weight.
A stiffer foil for grilling can also be used on the bulbs themselves, it can be wound into a spiral with an overlap, to fly next.
Letovat sa to da priamo na rure, using the common. 100W transformer solder and aluminum brazing liquid, it's good to practice on a piece of foil first.
It is optimal for an amateur construction to use discarded Al foil from an outlet store for yogurt cups, or similarly cheap solutions.
I created the internal lines of the leads to the dipoles from straws, which I took from the decoration in the bar. The length is approx. 1 m, but you can also use shorter straws stuck together from some fast food.
I put these straws through several layers of expansion pads cut from the bottom of a PET bottle.
In this way, during and after assembly, the drives will maintain the exact distance and cannot move during handling and transportation.
Their position in relation to each other and to one bulb is very critical.
I wound the matching transformer from the wires of,5mm of FTP/UTP cables, connected to each other and soldered together, they did not cause a significant problem.
They formed a winding of 128 turns.
They formed the primary winding of the transformer 3 zavity With 2.5mm wire
The setting consisted in finding the optimal number of turns on the secondary side of the transformer.
The range of operation was very narrow, approx. 20kHz.
Then it was necessary to change the branch.
Efficiency quite sufficient, even though I think, that probably a large part of the energy emitted from ant. sa absorbovala v blizkom okoli anteny.
In the open space, it appeared roughly as an equivalent invert in a 2x 18.8m dipole suspended on a 6m pole (NVIS ant.).
The characteristics of the EH antenna are similar to magnetic slot antennas.
First, a narrow operating frequency, but especially with an extremely high electromagnetic field in the vicinity of the antenna.
The most critical point is the center of the EH antenna dipole, where an extremely high VF voltage appears.
In this place, if the insufficiently dimensioned plastic is used, a HV breakdown will occur, or matrial charring.
The dilation should be between the spokes around 1-1,5 diameter of the circumference of the support pipe.
As the distance increases, the decreasing capacity begins to have a negative effect “dipole” at a smaller distance there is a risk of a breakdown.
A basic condition for a functional EH antenna, the transformation and optimal transformer pull-up by the dipole capacity of the EH antenna is suitably designed.
Moisture and a change in the environment around the antenna are also problematic.
If I find, I will send a photo.
The antenna is interesting for mobile operation, when it is not possible to build a different sized antenna.
It is more effective than an extremely shortened mobile antenna.
For multiple bands, you need to have a different antenna for each band, or solve exchangeable transformers.
If there is interest, I will also send pictures