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https://electronics.stackexchange.com/questions/3881/what-is-a-50-ohm-antenna-how-would-you-make-one

A "50 ohms antenna" is just an antenna that has a resistive impedance of 50 Ω, but any antenna can be a 50 Ω antenna by adjusting the length of the elements and/or their internal capacitive and inductive couplings and/or by adding inductive or capacitive components.

The antenna impedance is not related to physical constraints regarding its ability to radiate. The only physical impedance independent of the antenna is the free space impedance (376 Ω) but the antennas don't need this impedance. To be effective, they only need to reduce conductor resistance and eliminate capacitive and inductive impedance, so that it is mainly the radiation resistance that the transmitter sees. The radiation resistance is the equivalent load resistance fed by the transmitter, but whose energy is radiated and not transformed into heat as in an ordinary resistance. The art of making an antenna is therefore to ensure that the total resistance of the antenna is as close as possible to the radiation resistance and its impedance is purely resistive.

One of the simplest effective antennas (but not very directional) is the dipole antenna. As its impedance is 73 Ω, it adapts directly to the impedance of 75 Ω of common coaxial cables, and can be connected to a transmitter/receiver of 50 Ω even without an impedance transformer, with very satisfactory results. It is the best choice for beginners who want to build an antenna.
With two common telescopic antennas, you can easily make an adjustable dipole from 80 MHz to 600 MHz. I built two of these for all my tests.



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adjusting the length of the elements and/or their internal capacitive and inductive couplings and/or by adding inductive or capacitive components.
To increase the length of the antenna I add a length of wire loosely curled(to save space). The diameter is greater than the field of this added coil so the inductance is kept small? Tighter coil and smaller wire increases inductance.


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To increase the length of the antenna I add a length of wire loosely curled(to save space). The diameter is greater than the field of this added coil so the inductance is kept small? Tighter coil and smaller wire increases inductance.

Hi giantkiller

The gain of using a thick wire rather than a thin one, has the main advantage of increasing its surface area, thus reducing the disadvantage of the skin effect. The interest is not necessarily obvious near the end of an antenna element because we have there the least current. At the end the current is zero and the voltage is maximum.

It should be noted that this addition also has a capacitive effect that will go in the same direction as the effect of the coil inductance: lower the tuning frequency. For example, terminal conductors are often placed at the end of a vertical quarter-wave antenna, but perpendicularly. They allow to shorten the length thus the height to less than 1/4 wavelength. This is interesting for AM broadcasting on the lower frequencies of the bands. A large terminal coil can have a similar capacitive effect.



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Thanks for this.The basis for this question is pertaining to the schematic attached.
My quandary has always been (because of an attitude of perfection) antennas are made specific to resonate at a certain single or range of frequencies. But then components are added to shift that range. So my curiosity asks why would one make a specific antenna and then have to adjust the resonance point away from the natural resonant frequency? If one were working at the certain frequency wouldn't it be best to make the antenna fit that then add components to enhance the antenna at the natural frequency? And I also have computed the harmonics of the natural frequency into an oscillator in the TTL range of operation. But does that diminish to operative characteristics? My next computation would then find the harmonic that is closest to a 3rd, 5th, 6th, 7th or 9th harmonic.


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So my curiosity asks why would one make a specific antenna and then have to adjust the resonance point away from the natural resonant frequency? If one were working at the certain frequency wouldn't it be best to make the antenna fit that then add components to enhance the antenna at the natural frequency?

Think of Tesla's mechanical oscillator that he almost brought buildings down with. Many times you don't want the exact resonant frequency because the device would then self destruct and possibly take other valuable materials/devices with it.
   

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Think of Tesla's mechanical oscillator that he almost brought buildings down with. Many times you don't want the exact resonant frequency because the device would then self destruct and possibly take other valuable materials/devices with it.
The force is strong with this one.


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Thanks for this.The basis for this question is pertaining to the schematic attached.
My quandary has always been (because of an attitude of perfection) antennas are made specific to resonate at a certain single or range of frequencies. But then components are added to shift that range. So my curiosity asks why would one make a specific antenna and then have to adjust the resonance point away from the natural resonant frequency? If one were working at the certain frequency wouldn't it be best to make the antenna fit that then add components to enhance the antenna at the natural frequency? And I also have computed the harmonics of the natural frequency into an oscillator in the TTL range of operation. But does that diminish to operative characteristics? My next computation would then find the harmonic that is closest to a 3rd, 5th, 6th, 7th or 9th harmonic.

The idea that there would be a "natural frequency" is based on nothing more than impedance matching. It is arbitrary. For example, a "half-wave" dipole would have a very poor efficiency if used with an impedance transmitter of 300 ohms instead of 50 or 75 ohm, even for a frequency with a wavelength equal to twice its length.

The "natural frequency" is only the ability of the combination [antenna + transmitter output circuit (or receiver input) + transmission line] to favour current in the radiation resistance.

There is no theoretical need to have antennas related to wavelength, they are only engineering needs to optimize currents and fields. Any variable current flowing in a conductor radiates, it depends only on the intensity of the current and the radiation resistance. 
But antenna construction with elements multiples of the quarter-wave or half-wave, generally facilitates adaptation to the common impedance of transmitters, reduces the inductive or capacitive components of the impedance, and optimizes the radiation resistance in comparison to the conductor resistance, often with a simple mechanical design. So we use them instead of just any piece of wire with an added tuning circuit.

In the case of an antenna shortened by the addition of coils or terminal capacities, coils and capacities do not contribute to radiation or very little, but contribute to losses and degrade the ratio between radiation resistance and conductor resistance. It is therefore in our interest to avoid them. If you want a possible adjustment, you can always make the elements a little longer than necessary and then cut them gradually to reach the optimum.
« Last Edit: 2019-02-25, 10:37:32 by F6FLT »


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The big idea of the antenna, and it took me a while to understand the consequences, is as follows. It is better understood in the case of the reception I will take, but the effect is always reciprocal.

The local ambient electromagnetic field from a remote transmitter creates an induced current in the antenna. Lenz's law causes this induced current to create an electromagnetic field that opposes the ambient field.
However, in a field, we have energy: the energy density is 1/2(Ɛ.E²+B²/µ), and the energy is conserved. So where does the energy from the ambient field go when the current in the antenna creates a field that opposes it?
Well, in the antenna current! So, thanks to the current induced by the external field, the more the antenna produces a field that opposes the ambient field in the largest possible volume, and the more energy is collected from this field. This needs the adaptation of the impedances of all the components constituting the circuit as a whole: receiver input+line+antenna.

This also introduces the idea of the electrical antenna volume, which is to be increased. With good design it can go far beyond the physical volume occupied by the antenna (this also explains, but only in reception, the considerable gain that can be expected from negative impedances, which by reinjecting energy opposite the ambient field, allow more energy to be recovered in the current. But that's another story...)
Of course if we want only a confined local field, for exemple for NMR applications, we don't need these considerations. It's another problem, especially because of standing waves.



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The big idea of the antenna, and it took me a while to understand the consequences, is as follows. It is better understood in the case of the reception I will take, but the effect is always reciprocal.

The local ambient electromagnetic field from a remote transmitter creates an induced current in the antenna. Lenz's law causes this induced current to create an electromagnetic field that opposes the ambient field.

One exception that we've seen on the bench is with iron/nickel wire. >:-)
Ferromagnetic wire can be induced at any angle while inside a changing magnetic field.  Instead of a reciprocal reaction, induction appears to occur through alternate saturation+desaturation of the wire itself (parametric variation of inductance).


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I think this is an excellent video for those reading here, this is similar to the inside of my STEAP TPU

https://www.youtube.com/watch?v=adJp1zO9qfo

Enjoy

Regards

Mike 8)


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Now if I replace the antenna with a coil the same question exists but with a different perspective:
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My quandary has always been (because of an attitude of perfection) coils are made resonate at a certain single natural frequency. The component has inherent inductance too. But then components are added to shift that range. So my curiosity asks what do we gain by making a specific coil and then have to adjust the resonance point away from the natural resonant frequency? If one were working at the certain frequency wouldn't it be best to make the coil fit that then add components to enhance the coil/circuit at the natural frequency? And I also have computed the harmonics of the natural frequency into an oscillator in the TTL range of operation. But does that diminish to operative characteristics? My next computation would then find the harmonic that is closest to a 3rd, 5th, 6th, 7th or 9th harmonic.
Because in using the windings to produce a magnetic field we want to use the external field in a near field expression. And at resonance we get strong field that costs less energy using the swingset analogy than off resonance.
My basic tenant is to add a capacitor to the coil to promote the natural resonance other than pick another resonant point.
« Last Edit: 2019-02-26, 00:04:14 by giantkiller »


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Well, well, well:https://futurism.com/room-temperature-superconductor-patent?utm_source=Digest&utm_campaign=d4e51cca9b-EMAIL_CAMPAIGN_2019_02_25_06_02&utm_medium=email&utm_term=0_03cd0a26cd-d4e51cca9b-246559249&mc_cid=d4e51cca9b&mc_eid=a666f8a7ec
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Pais’ application describes a wire consisting of a metal coating over an insulator core. An electromagnetic coil surrounds the wire, and when activated by a pulsed current, this coil causes a vibration that allows the wire to act as a superconductor at room temperature, according to the application.


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One exception that we've seen on the bench is with iron/nickel wire. >:-)
Ferromagnetic wire can be induced at any angle while inside a changing magnetic field.  Instead of a reciprocal reaction, induction appears to occur through alternate saturation+desaturation of the wire itself (parametric variation of inductance).

There is no exception. It is question of electromagnetic waves, i.e. radiation, not of ordinary induction in the near field.
A field, even a variable field, is not a wave. The wave is formed at about a wavelength of the radiating element, this is called the far field. See here the difference between near field and far field. A wave is a combined autonomous E and B field that propagates at a speed c=1/√(Ɛ.µ).

If your working frequency is 1 Mhz, you must be 300 m away to talk about electromagnetic waves. At 100 KHz, you must be 3 Km away. At 10 KHz, you must be 30 Km away....
If you are at less than a half-wavelength, what you see is only the near field, which is captive, not a wave, completely linked to the current generating it, the energy being constantly exchanged between the field and the current. It is remaining in the system, it is not radiated. E and B are not perpendicular and can be everything, not related to the Poynting vector. For such a near field, you do not need an "antenna", an inductive coupling from a coil is sufficient. An antenna is only made to promote the formation of the far field, i. e. the radiation.

Anything like a ferromagnetic wire or any wire can be induced at any angle by a near field, the only requirement is that field lines cross the circuit surface somewhere, if we are speaking about induced current (if it's induced magnetization, it's obvious).





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If you are at less than a half-wavelength, what you see is only the near field, which is captive, not a wave, completely linked to the current generating it, the energy being constantly exchanged between the field and the current. It is remaining in the system, it is not radiated. E and B are not perpendicular and can be everything, not related to the Poynting vector. For such a near field, you do not need an "antenna", an inductive coupling from a coil is sufficient. An antenna is only made to promote the formation of the far field, i. e. the radiation.
Having spent many years in industry dealing with near-field radar (mine detectors, metal detectors, missile and torpedo target proximity detectors) using both electric and magnetic fields I can tell you that the fields definitely propagate at light speed, they do not appear instantaneously.  While agreeing that energy appears to be constantly exchanged between the field and the source this tells me that there is propagation both ways.  Something propagates from the moving charges and something returns back.  It is difficult to visualize what those somethings are, call them what you like sub-photons, virtual photons whatever, but one thing I am sure of.  Space if full of these virtual particles and the source doesn't shoot them out willy-nilly, the propagation is linked to those received from space.   Thus our concept of a near-field energy is really just a change in the pattern of the virtual particles surrounding the source, a change from so called "flat space" where the pattern of all the virtual particles passing through is the same everywhere.
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Gk   nice find!
Regarding the RTSC patent application, note that abrupt mechanical vibration is a key factor. Phase transition at the insulator/conductor boundary is also claimed to play a role. Ordinary aluminum can be the thin film material.

I'll read it further to see if this lies within the realm of home experimentation.

Smudge: I get it regarding your last post here.


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Having spent many years in industry dealing with near-field radar (mine detectors, metal detectors, missile and torpedo target proximity detectors) using both electric and magnetic fields I can tell you that the fields definitely propagate at light speed, they do not appear instantaneously.  While agreeing that energy appears to be constantly exchanged between the field and the source this tells me that there is propagation both ways.  Something propagates from the moving charges and something returns back.
...

Nothing goes faster than the speed of light. So is the near field. It expands/contracts around conductors carrying a varying current. It does so at the speed of light, which means that a point at a distance d from the conductor will not feel a change in field strength until a time t=d/c after the current change. Nevertheless, this field does not propagate as a wave because it is not autonomous.

It is only when the round trip is too far from the current source that the field beyond separates, can no longer return to the current source, becomes autonomous and propagates as an EM plane wave as shown on the image taken from Wikipedia and that I completed.

Below this distance of the wavelength order, E and B do not form a plane wave and are not perpendicular, it is not an electromagnetic wave but a "quasi-static" field, such as a standing wave, despite its influence going back and forth at the speed of light. That's why it is noted "reactive" and "non radiative".




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Gk   nice find!
Regarding the RTSC patent application, note that abrupt mechanical vibration is a key factor. Phase transition at the insulator/conductor boundary is also claimed to play a role. Ordinary aluminum can be the thin film material.

I'll read it further to see if this lies within the realm of home experimentation.
...

Hi Ion,

It sems it could be within the realm of home experimentation, we have to learn how to make the coating, but we have also to know the powers needed for the pulses and vibrations. I see no mention about that.

The patent has a reference to another interesting paper of the inventor Salvatore Cezar Pais (US Department of Defense/Navy) The high energy electromagnetic field generator. You can download it from sci hub, using the DOI.

As for the superconductor, his method is to shake matter by various means (rotations, non-linear vibrations) but at disproportionate levels: frequencies in the range of 109 to 1018 Hertz, field intensity values in the range1024 to 1028 Watts/m2, all using a 2 m diameter disc rotating at 30000 RPM and loaded at 50000 Coulombs!... for the propulsion of a spacecraft by interacting with the quantum vacuum which becomes polarized and exerts a negative pressure.

He refers to Puthoff and Haish who are not unknown to me more for their innovative ideas that can make us dream, than for the technology that their ideas could have generated and of which I see no trace anywhere.
But if the patent really works, it would restore credibility also to this whole field of propulsion and inertia manipulation.



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Nothing goes faster than the speed of light. So is the near field. It expands/contracts around conductors carrying a varying current. It does so at the speed of light, which means that a point at a distance d from the conductor will not feel a change in field strength until a time t=d/c after the current change. Nevertheless, this field does not propagate as a wave because it is not autonomous.

It is only when the round trip is too far from the current source that the field beyond separates, can no longer return to the current source, becomes autonomous and propagates as an EM plane wave as shown on the image taken from Wikipedia and that I completed.

Below this distance of the wavelength order, E and B do not form a plane wave and are not perpendicular, it is not an electromagnetic wave but a "quasi-static" field, such as a standing wave, despite its influence going back and forth at the speed of light. That's why it is noted "reactive" and "non radiative".
I understand all that, it's text book stuff, I was brought up on it.  But a field is something we measure, and if we measure over ever smaller time increments we find that the field effect becomes quantized, the field effect is made up of individual quanta arriving at the measurement point.  Then it makes no sense to describe a photon as a wave packet, it is more like a packet of quanta arriving with their spacing associated with a wavelength.  For a photon to be associated with a frequency there must be a minimum number of quanta appropriately spaced.  Also words like "fields expanding/contracting" or "fields separating" have little meaning with regard to what is really happening with those quanta, those virtual particles arriving at our measurement point.

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Nothing goes faster than the speed of light.
Quantum mechanics proves differently. Action at a distance. But the distance doesn't matter...
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I'll read it further to see if this lies within the realm of home experimentation.
Doesn't anybody see the TPU in there? We are already doing it...
A helical antenna wrapped around a charged conductor. Look at Wattsup's experiments.
Or is somebody waiting to publish a white paper when its safe to claim the glory?


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It's interesting that the USPO seems to accept applications for ideas that seem to be untested. The RTSC patent app seems to say "if it could work, it might work like this"

I have downloaded but not yet reviewed his other two entries, one of which was granted, the other is an app waiting for approval


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I understand all that, it's text book stuff, I was brought up on it.

It explains why your objection of the speed c of the near field doesn't invalidate the fact that it doesn't propagate.
A propagation is a radiation when it's question of wave. A "radiation is the emission or transmission of energy in the form of waves (or particle)". The near field doesn't propagates, there is not even a single wavelength in the volume where it's created, it's not a wave but a varying field.

Quote
But a field is something we measure, and if we measure over ever smaller time increments we find that the field effect becomes quantized, the field effect is made up of individual quanta arriving at the measurement point.  Then it makes no sense to describe a photon as a wave packet, it is more like a packet of quanta arriving with their spacing associated with a wavelength.  For a photon to be associated with a frequency there must be a minimum number of quanta appropriately spaced.  Also words like "fields expanding/contracting" or "fields separating" have little meaning with regard to what is really happening with those quanta, those virtual particles arriving at our measurement point.

Smudge

"fields expanding/contracting" has been used in the context of classical physics, not QM. "Field lines expanding/contracting" would have been better than "field", but it's just an image. We all know what a magnetic field is in classical physics, assignments of vectors to points in space.

In any case, a propagating photon is really a wave packet. See https://physics.aps.org/articles/v5/86 .
"A pulse of light can have almost any shape in space and in time, determined by the amplitudes and phases of its frequency components.
Surprisingly, single photons can also be generated in a variety of complex shapes. "



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It's interesting that the USPO seems to accept applications for ideas that seem to be untested. The RTSC patent app seems to say "if it could work, it might work like this"

I have downloaded but not yet reviewed his other two entries, one of which was granted, the other is an app waiting for approval

The "inventor" has two other even more exotic patents:
A "High Frequency Gravitational Wave Generator" and a "Craft using an inertial mass reduction device"!

His references to Harold Puthoff in support of some of these patents are worrying. Harold Puthoff is indeed one of the scientists in charge of the 1970s experiments on Uri Geller at the Stanford Research Institute. He concluded in the final report that Uri Geller had psychic powers, which I already mentioned here. These experiments were then revealed to have flaws everywhere (Puthoff is an "engineer and parapsychologist", not a physicist).

Also the principle of HFGW was invalidated, the possible signal it would generate being demonstrated at a level many orders of magnitude lower than this exotic theory predicted.

The author of this patent therefore seems to me to belong more and more to this lineage of Puthoff et al., from which nothing has ever come out of their ludicrous ideas.
I regret that I became enthusiastic about this announcement. What is amazing is that the US government endorses this kind of patent, and pays for it.


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The "inventor" has two other even more exotic patents:
A "High Frequency Gravitational Wave Generator" and a "Craft using an inertial mass reduction device"!

His references to Harold Puthoff in support of some of these patents are worrying. Harold Puthoff is indeed one of the scientists in charge of the 1970s experiments on Uri Geller at the Stanford Research Institute. He concluded in the final report that Uri Geller had psychic powers, which I already mentioned here. These experiments were then revealed to have flaws everywhere (Puthoff is an "engineer and parapsychologist", not a physicist).

Also the principle of HFGW was invalidated, the possible signal it would generate being demonstrated at a level many orders of magnitude lower than this exotic theory predicted.

The author of this patent therefore seems to me to belong more and more to this lineage of Puthoff et al., from which nothing has ever come out of their ludicrous ideas.
I regret that I became enthusiastic about this announcement. What is amazing is that the US government endorses this kind of patent, and pays for it.

Agreed on all points especially the last where taxpayers actually fund this.


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