Antenna of this shape? What is the benefit?

[qnach]

Is there a (dielectric) antenna of this shape

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i.e. a ladder? What is the good for such antennas?

 

[davenn]

View attachment 218273Is there a (dielectric) antenna of this shape
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i.e. a ladder? What is the good for such antennas?

have never seen an antenna like that...
where did you find this ?

 

[NascentOxygen]

View attachment 218273Is there a (dielectric) antenna of this shape

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i.e. a ladder? What is the good for such antennas?

You wrote "dielectric", but perhaps you meant "dipole"? The folded dipole might resemble what you have in mind, it is folded to reduce its span, and represents a compromise. It's one way to squeeze an antenna for longer wavelengths into a restricted space.

 

[berkeman]

View attachment 218273Is there a (dielectric) antenna of this shape

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i.e. a ladder? What is the good for such antennas?

Do you have a picture of such an antenna? If not, can you use Google Images to find one?

Does it look like the folded dipole suggested by @NascentOxygen ?

Or could it just be a Balanced Feedline to a dipole antenna?

http://4.bp.blogspot.com/-E7_DNGw_UgA/UFxWVfdGaRI/AAAAAAAAABw/Tq492Jf4S-o/s1600/Dipole-Ladder.gif

 

[qnach]

You wrote "dielectric", but perhaps you meant "dipole"? The folded dipole might resemble what you have in mind, it is folded to reduce its span, and represents a compromise. It's one way to squeeze an antenna for longer wavelengths into a restricted space.

Many thank for your reply.
No, I mean "dielectric". I know most antenna is made of conductor. But dielectric can also be used as antenna...it may have different design parameters...

I do not mean "folded dipole". I indeed mean those ladder shape. I have googled and found some ladder shaped antenna in those ham's website. But they do not explain what is the benefit for using a ladder shape.

 

[qnach]

Do you have a picture of such an antenna? If not, can you use Google Images to find one?

Does it look like the folded dipole suggested by @NascentOxygen ?

Or could it just be a Balanced Feedline to a dipole antenna?

http://4.bp.blogspot.com/-E7_DNGw_UgA/UFxWVfdGaRI/AAAAAAAAABw/Tq492Jf4S-o/s1600/Dipole-Ladder.gif
View attachment 218292

The picture you quoted is indeed nice. But I do not understand what is the feed-line for? Why do they need a feedline of that peculiar shape?

I got this idea because DNA is a ladder shape molecule. Some said it is a conductor, but I would say it is a dielectric. How well could it be, if functioned as an antenna? ...There will have a question where is the feedline?

 

[berkeman]

I got this idea because DNA is a ladder shape molecule. Some said it is a conductor, but I would say it is a dielectric. How well could it be, if functioned as an antenna? ...There will have a question where is the feedline?

AFAIK, the function of DNA and its replication has nothing to do with any conductivity, and almost certainly nothing like antenna Tx/Rx action. I can move your thread to the Biology forum instead, if that is mostly what you are asking...

 

[NascentOxygen]

I indeed mean those ladder shape. I have googled and found some ladder shaped antenna in those ham's website. But they do not explain what is the benefit for using a ladder shape.

Please provide a link to the illustration you are referring to.

 

[NascentOxygen]

The picture you quoted is indeed nice. But I do not understand what is the feed-line for? Why do they need a feedline of that peculiar shape?

The feedline needs to have an impedance that matches the characteristic impedance of the antenna (and also the output impedance of the transmitter), so energy is not reflected at the junction. The horizontal lines represent plastic to keep the conductors at a fixed spacing. Parallel conductors spaced apart is typical of 300Ω impedance, whereas coaxial cable is used for 50Ω or lower. If unequal impedances are used, a transformer is needed to transform the impedance so feeder and antenna appear matched.

 

[qnach]

The feedline needs to have an impedance that matches the characteristic impedance of the antenna (and also the output impedance of the transmitter), so energy is not reflected at the junction. The horizontal lines represent plastic to keep the conductors at a fixed spacing. Parallel conductors spaced apart is typical of 300Ω impedance, whereas coaxial cable is used for 50Ω or lower. If unequal impedances are used, a transformer is needed to transform the impedance so feeder and antenna appear matched.

1. The picture you shown is not only parallel lines. There are some spacers? Is that only spacer which has no function for the line?
2. My interest is in the antenna instead of the feedline. An antenna of the ladder shape. Will it has better performance? Has anyone studied such antenna?

 

[berkeman]

1. The picture you shown is not only parallel lines. There are some spacers? Is that only spacer which has no function for the line?
2. My interest is in the antenna instead of the feedline. An antenna of the ladder shape. Will it has better performance? Has anyone studied such antenna?

Please, I would prefer that you do a lot more work on your question, and ask us to explain the parts of technical links that you don't understand.

You posted that you think DNA communicates with antennas. That's not good.

You posted that you think antennas use dielectrics to work to conduct currents, instead of using wires to conduct RF currents to couple to radiated fields. Not good.

You refuse to post the source of your question. Not good.

Please impress us with your next post in this thread...

 

[berkeman]

I got this idea because DNA is a ladder shape molecule. Some said it is a conductor, but I would say it is a dielectric. How well could it be, if functioned as an antenna? ...There will have a question where is the feedline?

If your main misunderstanding is because of this, that is fine. DNA does not use antenna concepts to function.

 

[NascentOxygen]

1. The picture you shown is not only parallel lines. There are some spacers? Is that only spacer which has no function for the line?

The spacers are plastic, and are referred to as the dielectric. They give the transmission line important capacitive characteristics.

2. My interest is in the antenna instead of the feedline. An antenna of the ladder shape. Will it has better performance? Has anyone studied such antenna?

Almost anything can be used as a radiating surface. Two long thin conductors joined by many short thin conductors would be electrically the same as a single long conductor, at long wavelengths. At shorter wavelengths it almost certainly would have been experimented with, radio experimenters have been a very enterprising breed of hobbyist, but unless it were found to offer advantages that other simpler lighter shapes don't, then it would have been discarded. You say you have found a photo, but I'm still waiting for the link. In photos it is often difficult to distinguish conductor from insulator, e.g., aluminium tube from PVC pipe joined to the aluminium.

 

[Baluncore]

The Sterba and Bruce antennas look like ladders.
DNA cannot be an antenna because it is a twisted pair. The radiated fields will tend to cancel.

I seem to remember a similar question about making a dipole array to emulate chlorophyll. Chemistry is really an infrared technology with some coloured visible light effects where metals are involved. That cannot be analysed as waves and dipoles but must be analysed using quantised photons. The same goes for DNA.

 

[vk6kro]

The ladders in feed lines or antennas are almost always there to hold the wires at a fixed spacing.

They are made of some suitable insulating material like ceramic or low loss plastic.

The actual high frequency signal is an electrical AC voltage which has to travel in a metallic conductor until it is radiated.

A feed line with the conductors widely spaced enough to need spacers would be fairly high impedance.
It would not be needed in an antenna which has a low impedance feed point like the diagram in this question.Folded dipoles are the same length as normal dipoles, but they may be used because they are mechanically more rugged and because they can be grounded at their centre point.
They may have ladder type insulators, but this is only for mechanical stability. They play no part in radiating a signal.

 

[Baluncore]

The actual high frequency signal is an electrical AC voltage which has to travel in a metallic conductor until it is radiated.

Actually a voltage field is guided by the two conductors, while the magnetic fields due to the equal and opposite signal currents on the surface of the conductors, sums between the conductors. That makes a crossed EM field between the conductors. The cross product of the E and M is a Poynting vector between the conductors carrying energy from the generator to the load. So the energy does not travel in the conductors, energy travels between the conductors, along the ladder line, crossing the middle of every insulator between the wires. When that energy reaches the antenna it is spread out by the dipole and radiated.
https://en.wikipedia.org/wiki/Poynting_vector

 

[vk6kro]

Actually a voltage field is guided by the two conductors, while the magnetic fields due to the equal and opposite signal currents on the surface of the conductors, sums between the conductors. That makes a crossed EM field between the conductors. The cross product of the E and M is a Poynting vector between the conductors carrying energy from the generator to the load. So the energy does not travel in the conductors, energy travels between the conductors, along the ladder line, crossing the middle of every insulator between the wires. When that energy reaches the antenna it is spread out by the dipole and radiated.
https://en.wikipedia.org/wiki/Poynting_vector

The fields around a conductor carrying radio frequency energy are the result of the current and voltage in the conductor.

You can easily verify this. Just put a 1mm break in an antenna or a feed line and observe the effect on the antenna.

The current is totally disrupted and so is the transfer of power to the antenna.

Without the current and voltage in the conductor, there is no field.

 

[NascentOxygen]

Thanks to all contributors. I believe the poster has had his question answered.

Thread closed.