The first radar I worked on used a dummy load like the termination in your directional coupler and it contained a ferrite element. A bit larger as it was a L band radar around 1.2 GHz. The dummy load was air cooled and you could shoot 20 MW pulses into it. This radar system normally ran around 2.5 MW, had two complete transmit/receive channels. It had a 4 port motorized waveguide switch that connected one channel to the antenna and the other channel to the load. Regards, David
Definitely wizardry in its blackest form. Galileo and his telescope, van Leeuwenhoek and his microscope, Newton and his prism, Hertz and his antenna, Max Planck and his black body radiator, Feynman and his diagrams, and so many others, so that we can sit there with our eyes glued to our screens watching videos :-)
What an ingenious design! Thanks for your explanation and presentation 👍 And as you suspected, it must have been made of graphite that would absorb residual RF (or light) and at the same time provide a very shiny reflecting surface. You can confirm that it is not ferrite by bringing a permanent magnet near to it. Ferrites would be attracted by magnets. De VU2RZA
Might also be worthwhile to mention the ~impedance of rectangular waveguide which isn't close to 50 ohms. I would guess the termination is composed of ferrite unless it's very lightweight------>then maybe a carbon composite.
I wonder if a light trap can be used for measuring the power of a laser beam. Measure the temperature over time, knowing the mass, specific heat, dissipation etc. Nice waveguide coupler, looks extremely well made. Very interesting resistor!
Sounds real good. We can use the resistivity measurement ( which is a function of temperature) to infer temperature. But still will be too slow. Instead, we can use a beam splitter or something like directional coupler and send the output to photodetector, this probably is faster and you can detect the modulation of the leaser beam. Even for high power leasers we can use diffraction by air molecules and use photodetector perpendicular to the beam a given distance from center of the beam to detect the power of the beam faster.
Negative. It has a totally different mechanism; yes, it is gravity that is at work. Gravity is the weakest of the four known fundamental forces with a magnitude of around 1/40th of the strong force. But in a black hole beyond the event horizon it engulfs everything that falls in and the escape velocity is infinite. Light itself is not able to escape. Free space impedance doesn't play any role here. De VU2RZA
@@IMSAIGuy 0 ohm should be fully reflective like metals or super conductors. Here is the limit of classical EM theory and we should consider Quantum nature of light. Any ways light in metals takes the form of evanescent wave in which jw turns into w.
@@subramanianr7206 As you know speed of light inside metal (wave velocity) is higher than speed of light in free space. We really do not know whats going on inside a black hole. We just guess by extrapolating with the models that we tested outside black hole.
@aduedc black hole, its escape velocity, and so on are not wild guesses, as you may want to assume. And light inside metals has velocity more than that in free space..? Great discovery indeed... De VU2RZA
Very nice. I haven't thought about razor blade traps in better than 30 years. I learned the concept from my them lab PI. A similar trap model is used for heat shielding (IR) on the Webb telescope. IIRC, smarterveryday dug into that application a few years ago.
It remind me on a LNC from a Satellite Antenna. Inside you finde to similar looking parts, for my thinking, on terminats the horizontal Signal and the other terminats the vertical Signal.
That principal seems to be the same used in the wall-mounted baffles in an anechoic chamber, right? As a photographer as well I am always fascinated by the optical and microwave analogs of our low-frequency gear. Attending my fist Microwave Update give me my fist look at all that 'plumbing. UHF/SHF should be more approachable with the new Icom 905 system. But not cheap. Most of my recent photography has been digital Infrared, using hacked Sony 'nightshot' cameras, Do you know about that? You can see explanations and examples on YT. 'Xray vision!
Thanks. Ever since I got a TinySA Ultra and a NanoVNA so I could work up into microwave regions I have been curious about the implementation of the hardware.
Rectangular waveguide is the most common because it supports both Transverse Electrical (TE) and Traverse Magnetic (TM) modes of RF transmission with TE10 having the least attenuation. There are round "waveguides" also known as coaxial cables that are used in microwave systems that use Transverse ElectoMagnetic (TEM) mode and requires two conductors (waveguide is a single conductor!) Radar systems use both TE mode in waveguide and TEM in the rotary joint.
Just to check my understanding, there will be no reflection, so it will look exactly like a 50 ohm termination. If you hooked your VNA to it you would see a purely resistive 50ohms at the wavelength of thr guide?
@@IMSAIGuy The impedance of free space is 377 Ohms. It is sqrt(u0/e0). Permeability of free space is u0, permittivity of free space is e0. I did study that back in physics E&M class way back in the day.
I know little about RF. Would it be more accurate to say the RF trap attenuates the signal by the equivelant of 50 ohms in decibles? Just curious. Thans ISMAI Guy I learned a lot as usual, the light trap using razor blades was very cool. Take care.
50 ohms really doesn't enter into this. Impedance of the wave guide can be anything and the RF trap will still work. There is nothing magical about 50 ohms.
The first radar I worked on used a dummy load like the termination in your directional coupler and it contained a ferrite element. A bit larger as it was a L band radar around 1.2 GHz. The dummy load was air cooled and you could shoot 20 MW pulses into it. This radar system normally ran around 2.5 MW, had two complete transmit/receive channels. It had a 4 port motorized waveguide switch that connected one channel to the antenna and the other channel to the load. Regards, David
everybody loves the RF instruction,... thank you!
very interesting mechanics. pretty much equivalent to sound traps known as an-echoic chambers.
BEST video I've seen on this channel so far. EXCELLENT!!!
Definitely wizardry in its blackest form. Galileo and his telescope, van Leeuwenhoek and his microscope, Newton and his prism, Hertz and his antenna, Max Planck and his black body radiator, Feynman and his diagrams, and so many others, so that we can sit there with our eyes glued to our screens watching videos :-)
RF Is the "blackest" of black art to me.
Awesome video. Thank you!
What an ingenious design! Thanks for your explanation and presentation 👍 And as you suspected, it must have been made of graphite that would absorb residual RF (or light) and at the same time provide a very shiny reflecting surface.
You can confirm that it is not ferrite by bringing a permanent magnet near to it. Ferrites would be attracted by magnets.
De VU2RZA
slightly magnetic
@@IMSAIGuy ok, then it cannot be pure graphite alone. Thank you.
De VU2RZA
Might also be worthwhile to mention the ~impedance of rectangular waveguide which isn't close to 50 ohms. I would guess the termination is composed of ferrite unless it's very lightweight------>then maybe a carbon composite.
I wonder if a light trap can be used for measuring the power of a laser beam. Measure the temperature over time, knowing the mass, specific heat, dissipation etc.
Nice waveguide coupler, looks extremely well made. Very interesting resistor!
Bolometer
Sounds real good. We can use the resistivity measurement ( which is a function of temperature) to infer temperature. But still will be too slow.
Instead, we can use a beam splitter or something like directional coupler and send the output to photodetector, this probably is faster and you can detect the modulation of the leaser beam.
Even for high power leasers we can use diffraction by air molecules and use photodetector perpendicular to the beam a given distance from center of the beam to detect the power of the beam faster.
That’s freakin awesome!!
Thanks, I learned something new.
I always pondered that black holes should be a perfect 377 Ohm load. ( i.e. the impedance of free space)
my guess would be zero ohms
Negative. It has a totally different mechanism; yes, it is gravity that is at work. Gravity is the weakest of the four known fundamental forces with a magnitude of around 1/40th of the strong force. But in a black hole beyond the event horizon it engulfs everything that falls in and the escape velocity is infinite. Light itself is not able to escape.
Free space impedance doesn't play any role here.
De VU2RZA
@@IMSAIGuy 0 ohm should be fully reflective like metals or super conductors. Here is the limit of classical EM theory and we should consider Quantum nature of light.
Any ways light in metals takes the form of evanescent wave in which jw turns into w.
@@subramanianr7206 As you know speed of light inside metal (wave velocity) is higher than speed of light in free space.
We really do not know whats going on inside a black hole. We just guess by extrapolating with the models that we tested outside black hole.
@aduedc black hole, its escape velocity, and so on are not wild guesses, as you may want to assume. And light inside metals has velocity more than that in free space..? Great discovery indeed...
De VU2RZA
Very nice. I haven't thought about razor blade traps in better than 30 years. I learned the concept from my them lab PI. A similar trap model is used for heat shielding (IR) on the Webb telescope. IIRC, smarterveryday dug into that application a few years ago.
Very interesting! I never did any work with wave guides in my electronics career so this is all new to me!
This is excellent. Any chance you'd cover circulators?
yes several, search my channel for circulator
In anechoic chambers, the same principle is used
It remind me on a LNC from a Satellite Antenna.
Inside you finde to similar looking parts, for my thinking, on terminats the horizontal Signal and the other terminats the vertical Signal.
Great video! Maybe discuss waveguide gasket flanges sometime? Thanks!
just to seal in the dry air or nitrogen
That principal seems to be the same used in the wall-mounted baffles in an anechoic chamber, right?
As a photographer as well I am always fascinated by the optical and microwave analogs of our low-frequency gear. Attending my fist Microwave Update give me my fist look at all that 'plumbing. UHF/SHF should be more approachable with the new Icom 905 system. But not cheap.
Most of my recent photography has been digital Infrared, using hacked Sony 'nightshot' cameras, Do you know about that? You can see explanations and examples on YT. 'Xray vision!
Thanks. Ever since I got a TinySA Ultra and a NanoVNA so I could work up into microwave regions I have been curious about the implementation of the hardware.
I’m interested to know why wave guides are always rectangular cross section and not square, or round ??
Rectangular waveguide is the most common because it supports both Transverse Electrical (TE) and Traverse Magnetic (TM) modes of RF transmission with TE10 having the least attenuation. There are round "waveguides" also known as coaxial cables that are used in microwave systems that use Transverse ElectoMagnetic (TEM) mode and requires two conductors (waveguide is a single conductor!) Radar systems use both TE mode in waveguide and TEM in the rotary joint.
Just to check my understanding, there will be no reflection, so it will look exactly like a 50 ohm termination. If you hooked your VNA to it you would see a purely resistive 50ohms at the wavelength of thr guide?
yup
If your system is any other impedance then the absorber will look like that impedance.
@@herbertsusmann986 that's right, the waveguides are about 400 ohms,
@@IMSAIGuy The impedance of free space is 377 Ohms. It is sqrt(u0/e0). Permeability of free space is u0, permittivity of free space is e0. I did study that back in physics E&M class way back in the day.
I guess Silicon carbide
What if the laser light hits the apex of the pointy thing?
Is there a way to calculate the pointy resistor to absorb and then bounce back a harmonic to be able to get rid of it?
I don't understand your question, but I'm sure the answer is no
I know little about RF. Would it be more accurate to say the RF trap attenuates the signal by the equivelant of 50 ohms in decibles? Just curious. Thans ISMAI Guy I learned a lot as usual, the light trap using razor blades was very cool. Take care.
no that would not be more accurate
Thanks@@IMSAIGuy
50 ohms really doesn't enter into this. Impedance of the wave guide can be anything and the RF trap will still work. There is nothing magical about 50 ohms.