Cavity Filter Basics

[@w04h]

The dark magic of electronics

[@icebluscorpion]

Rather the CURSED! area of the Dark Magic Electronics XD

[@thePavuk]

University Inquisition was alread noticed.

[@JeffGeerling]

And the area where you find surprising results every time you try replicating the exact same physical experiment!

[@jonathanlister5644]

Excellent and elegant as always. This exemplifies the artiness of electronics!

[@trcwm]

Can’t wait for the practical measurements! 👍

[@inrit]

I have been waiting for a clear and concise video on cavity filters forever! Thank you so much!!!

[@TheDiveO]

having seen this some time ago in one or some of Curious Marc's vids, this is finally building the missing link to this dark art of trolling the rest of electronics!

[@deang5622]

"I signed up to a degree in electronic engineering, NOT plumbing!"

[@electronics.unmessed]

Good explanation! Thanks for sharing! 👍

[@fotografm]

Excellent video ! I appreciate your clear and thorough approach. This technology cannot be replaced by SDR when power is involved eg. in a transmitter. Keep up the good work !

[@ThermalWorld_]

Thanks for explaining Cavity filters.. Very black magic 😛

[@StreakyP]

great video many thanks... talking about amateur radio "abuse" of these things I have heard of aluminium beer kegs successfully being used as the conductive "cavity" for a VHF filter but the best one was a April fools joke about a 30' shipping container for a 7MHz (40 metre) cavity filter.

[@Dazzwidd]

I bet a shipping container wouldn't be big enough for 7mhz. 14mhz though 🤔

[@StreakyP]

@@Dazzwidd standard length 40 & 45 foot shipping containers should easily contain a 33 foot 7MHz quarter wave resonator.. but I do agree that finding a "dunk tank" big enough to silver plate it might prove a little difficult 🤪.... I just don't know how I'm going to find a suitable filter for my stacked & bayed rotatable rhombic antenna farm.

[@andrewmcfarland57]

Analog is king. 🙂

[@estebhano]

How is it response against temperature? In case the filter is in a cabinet expose to direct sun, external temperature could range 20° differential in a night-day cicle. Is the resonant frequency affected and how much? Thanks.

[@R2AUK]

Great topic 👍

[@tomgburklin1112]

thank you, beyond my brain to absorb all of it ... right now. but gets me thinking. -

[@tr_2sc1970]

I am a hobbyist and I experiment with RF, my mathematical knowledge is poor. I have a quartz oscillator ICD6233 programmed for 100MHz, but there are multiple harmonics and I need to boost the 400MHz while filtering out the rest. I need to also narrow the slopes of the frequency (in hobbyist terms) I need to suppress -filter out (attenuate) the grass (notch) before 400MHz and after it. Is it possible by using a cavity filter? I did experiment with LC Band pass filters shunt and series but I couldn't get the results I wanted. Can you suggest a solution? Thanks a lot.

[@byronwatkins2565]

The electric field is perpendicular to equipotentials (i.e. conductors). At 3:00, the electric field is radial rather than longitudinal.

[@FesZElectronics]

In the case of the resonator, the structure (at resonance) has opposing charges at the ends - when the top is positively charged, the bottom is negative; that is why the lines seem to go perpendicular. Even though its one piece of conductor, at high frequency it is not a equipotential - local bits are at different values.

[@andrewmcfarland57]

Can we see one of those nifty copper boxes on a VNA? 🙂

[@FesZElectronics]

Of course! I test all the filters I've built in the next episode.

[@BartKus]

Any chance for FEM of these filters? Like, what's an optimal coupling loop shape / position? Some coupling loops use flat wire instead of round. Why?

[@-Tris-]

And I still don't understand what's going on with the last filter I build. It was meant to be for 149 MHz but has a second dip at 137 MHz. Nice 2 meter bandpass, but that's not what I wanted.😅

[@johnpooley3]

Amazing, thank you

[@guytech7310]

I would have liked to see the design of those two sample filters you created. Design, construction, and testing. That would make a interesting video. For instance how did you spec out the size, positioning of the internal components & how to make any adjustments (presuming its possible with the construction method used.

[@joansola02]

Super interesting as always. Question: the 50 ohm source impedance in the models should be in series no? Or what is the effect of having this resistor in parallel with the voltage source?

[@FesZElectronics]

When modeling a voltage source, this is comprised of an ideal voltage source with a series resistor; when modeling a current source, its comprised of a ideal current source with a parallel resistor. If you add the resistor in parallel with an ideal voltage source it will have no effect (same for a resistor in series with the current source); from the "outside", an ideal voltage source, or an ideal voltage source with a parallel resistor behave in exactly the same way.

[@joansola02]

@@FesZElectronics Yes, yes! But at 5:30 you are using voltage sources. Therefore my comment . Thanks for this quick answer, and for your excellent videos!

[@FesZElectronics]

With voltage sources, if you right click on them directly, or going to "advanced", you have the option of defining the parasitics - series resistance and parallel capacitance; in the simulation, you can see under the "AC 1" parameter definition, the text "Rser=50" which is part of the voltage source definition -so the 50ohm series resistance is included into the voltage source, it does not have to be a dedicated external resistance.

[@joansola02]

@@FesZElectronics Oh I see. So the external resistor is just an adapted load resistor? this makes sense.

[@Jaunis100]

It iš source output resistane from signal , other----output- loud resistane.You must conect 50 om resistor ir you measure with big resistance voltmetr( and not conected any loud with 50 om input )

[@glenmartin2437]

Thanks.

[@treehouseskoolie2515]

Isn't this what Tesla was doing with wireless power and Wardenclyff?

[@thePavuk]

"The way how Machine God speaks with you depends on size of scented candles and distance between them during the ritual." - Tech-priest of Adeptus Mechanicus

[@GWorxOz]

gibberish. Sounds like a chipmonk

[@cold3lectric]

nah chipmunks have voices sped up and are very high pitched. "Aaaaaalvinnnnnn!"

[@mariuszwozniak6918]

Shut up angloid moron