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have never seen an antenna like that...qnach said: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.qnach said: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?qnach said: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?
NascentOxygen said: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 said: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
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...qnach said: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?
Please provide a link to the illustration you are referring to.qnach said: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.
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 said: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?
NascentOxygen said: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.
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.qnach said: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?
If your main misunderstanding is because of this, that is fine. DNA does not use antenna concepts to function.qnach said: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?
The spacers are plastic, and are referred to as the dielectric. They give the transmission line important capacitive characteristics.qnach said: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?
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.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?
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.vk6kro said:The actual high frequency signal is an electrical AC voltage which has to travel in a metallic conductor until it is radiated.
The fields around a conductor carrying radio frequency energy are the result of the current and voltage in the conductor.Baluncore said: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 purpose of an antenna with this shape is to improve the reception and transmission of electromagnetic waves. The shape of the antenna is specifically designed to capture and emit signals at a certain frequency, allowing for more efficient communication.
The shape of an antenna plays a crucial role in its performance. Different shapes are designed to operate at specific frequencies and have different radiation patterns. The shape also determines the impedance, gain, and directionality of the antenna.
Using an antenna with this specific shape can provide several benefits, such as improved signal strength, increased range, and better directionality. It can also reduce interference from other nearby signals, resulting in clearer and more reliable communication.
The size and weight of an antenna are directly influenced by its shape. Some shapes may require larger dimensions to operate effectively at a specific frequency, while others may be more compact and lightweight. The shape also affects the structural integrity of the antenna, which can impact its durability and weight.
While there are many benefits to using an antenna with this shape, there may also be some disadvantages. For example, some shapes may be more directional, making it challenging to receive signals from multiple directions. Additionally, the intricate design of some shapes may make them more expensive to manufacture.