Cavity filter Experiments

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#228 In this video I continue looking at cavity filters by performing some experiments on a set of practical builds. I start with a single resonator single port cavity just to confirm the simulation results; but from there I move onto a set of practical filter, looking at the construction methods that I used, the tools used for dimensioning and finally a look at the filters response.
Filter series:
Ep1 - Intro : • Intro to Filters
Ep2 - Passive RC Filters: • Passive RC Filters
Ep3 - Active RC Filters: • Active RC-filter Basics
Ep4 - More Active RC Filters: • MORE Active RC Filters
Ep5 - Introduction to LC Filters: • Introduction to LC Fil...
Ep6 - LC filter limitations: • Limitations of LC Filters
Ep7 - Piezo-Electric Filters: • Piezo-Electric Filters
Ep8 - Crystal Filter Measurements and Design: • Crystal Filter Experim...
Ep9 - Cavity filter Basics: • Cavity Filter Basics
Ep10 - Cavity filter Experiments: • Cavity filter Experiments
Ep11 - Stub filters: • Coax Stub Filters
Tools and calculator links:
www.changpuak....
coil32.net/onl...
rfshop.co.uk/m...
Special Thanks to all my supporters on Patreon!
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If you want to support the creation of more and better videos please consider checking out: / feszelectronics

Опубликовано:

8 сен 2024

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Комментарии : 32

@AKkarol7 Месяц назад

I work in electronics for 15 years know. Your videos are a true gifts. Many thanks

@electronics.unmessed Месяц назад

Thank you very much for sharing and explaining your courageous RF experiments results. 👍👍👍

@donepearce Месяц назад

Nice work. They all need adjustment to the coupling to flatten the tops, but they work, and they work well.

@FesZElectronics Месяц назад

I found that 2 things are quite difficult to get right - the exact adjustments of each resonator - to get the desired response shape; and the other is the coupling - you can get a better or worse result (higher or lower pass band attenuation) by changing the exact amount of coupling into the first and last resonator. So with the devices I've built, the coupling is adjusted by changing the exact tap point.

@donepearce Месяц назад

@@FesZElectronics Exactly what I would do

@donepearce Месяц назад

@@FesZElectronics Tuning resonators accurately is best done in time domain. Set the analyser by CF and Span. CF goes to the centre frequency of the filter. The span should be about 3 X the filter bandwidth. Now look at S11 in time domain and you will see three dips, one for each resonator. Tune them by making them as deep as possible. The resonators are now perfectly in tune, and all that remains is the coupling.

@tomyorados974 Месяц назад

@donepearce "look at S11 in time domain": Do you mean a Fourier transform of S11?

@donepearce Месяц назад

@@tomyorados974 Time domain is a selectable option on this analyser.

@BalticLab Месяц назад

Great video, as always! 🙂

@FesZElectronics Месяц назад

Thank you! I'm happy you enjoyed it!

@joshmyer9 Месяц назад

Nice explanation, with very approachable builds, thanks! Now I'm going to have to play with these even though I don't have any real application at the moment. (When do we get a diplexer video? 😅)

@ahbushnell1 Месяц назад

Good work. It would be interesting if you tunned the cavity screw live and show the change or sensitivity.

@ghlscitel6714 Месяц назад

Again, it's a thought-provoking video. Respect! Do you know the dielectric losses of the material of the helical coil supports?

@FesZElectronics Месяц назад

I used generic PLA, nothing special; but I guess there are better materials, anyway, you should be able to reduce losses by having a very low infill ratio - use the bare minimum plastic to support the structure.

@enriqueolivares119 Месяц назад

Muy buen video. Gracias por la calidad del contenido. Saludos.

@godarklight Месяц назад

Very nice work, I'm sure my construction would look more like VK3YE's video on cavity filters, but using the blank PCB's seems like a good approach for this type of thing.

@rl69782 Месяц назад

I'v found that silver plating the copper helps reduce losses. Also in your helical filters, the dielectric losses in your coil forms could be significant.

@FesZElectronics Месяц назад

I did think of trying to silver-plate one of these devices, but looking into the chemicals needed, I decided it was cheaper and safer not to try... maybe if you know a small workshop or company that can do it for you (I guess a jeweler) it might be relatively affordable. Did you ever silver-plate any electronic device?

@trcwm Месяц назад

The best video on practical cavity filters on RU-vid. Excellent work! ❤

@bg7jaf Месяц назад

Nice video!👍

@gfr2023 Месяц назад

5:00 not only a cylinder will be better but also using a pipe will save you a lot of time in construction. Great Job anyways

@y_x2 Месяц назад

Use of copper sheets and scissor is much easier to build. Copper sheet is available in any hardware store.

@johnwest7993 Месяц назад

Thank you. I was wondering about the thermal expansion/contraction effect from home-brew PCB material filter cans. They wouldn't really follow the expansion/contraction coefficient for pure copper. I suppose I will need to do thermal frequency shift experiments with the materials of interest. But even used commercially made cans are so expensive it might well be worth it for projects less important than a ham club repeater up on a mountain. Did you print your coil forms with some sort of polystyrene to keep the dielectric losses down, or was that not a concern?

@FesZElectronics Месяц назад

It is quite common to make PCB based filters - most transmission line filters are built on a PCB substrate when going for high frequencies; here you can work with FR4 when losses are not important or at relatively low frequnecy, or with some more exotic materials - like Rogers PCB when losses need to be minimized. Regarding the coil forms, I just used PLA, I was not trying to take too much care with losses though...

@accountant1653 Месяц назад

👍👍

@rocketman221projects Месяц назад

How much dielectric loss does the 3D printed coil form add to an otherwise identical 2M helical filter?

@liviu201 Месяц назад

9:03 - ...and using... What? :)))

@adrian_sp6def Месяц назад

Your callsign please?

@treehouseskoolie2515 Месяц назад

Aren't these the principles Tesla was trying to use to transmit power wirelessly with the wardenclyff cavity resonator?

@neon_Nomad Месяц назад

Id rather have a gravity filter. My house is full of it, and nothing i've tried works.

@andrewmcfarland57 Месяц назад

My HAMster wheel brain is trying to make me figure out how this would scale at 160 meters. #10 can? Steel 5 gallon paint bucket? 40 lb. propane canister? Of course, then i would need a legal-limit amp... (The dogs says I'm crazy, and to go to bed.)🙂

@FesZElectronics Месяц назад

A quarter wavelength at 160m is 40m.. I think a tank container is appropriate. It would be completely impractical, but what a sight to see it would be though.