DIY High Voltage Variable Capacitor
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- čas přidán 1. 08. 2024
- Prompted by the need for a high voltage variable capacitor to tune an (magnetic loop) antenna, I go through the calculations on how to make one using single sided PCB blanks. We also take a look at calculating capacitance using air and mixed dielectric materials.
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@tcurrentsource
www.thecurrentsource.com - Věda a technologie
Great to have you back! That capacitor stack looks really cool. Always nice when the math works out.
Fascinating stuff. I very much like how you've thought about the aesthetics of the capacitor and how robust it looks. As stylish and manly as a DYI cap will ever be! It'd be interesting to hear how it all comes together.
This is fantastic. I have a friend in Russia who had one of these capacitors in a picture. I cannot contact him so I am glad you made this video. Thank you.
I've been wanting to make a magnetic loop antenna for a while now, and this is great! Thanks! - WU2F
Thank you so much. I will copy this in full. Could you please post a brief video of your completed and installed capacitor? I am sure many of us would like to see it in action and so learn even more.
I am planning to build a mag loop of my own for use on 20m. I have ordered a VVC from Max-Gain Systems. Yet I enjoy looking at problems and have been thinking about the tuning capacitor issue. Thank you for showing the math behind this. I hope you will produce more videos as you develop your mag loop.
Thanks for the explanation and lack of a shaky camera.
Wow! This was fascinating! My maths isn't the best but with your help I was able to follow. I was particularly interested because I have a stack of old CDs and was wondering if I could cover them with copper tape, cut them in half and make an air variable capacitor. After seeing this, I may experiment. Thanks for taking the time to make your videos, I for one, appreciate them.
I like it! You do good work. I was contemplating the idea of using PCB material for a longwave antenna capacitor because it was easy to solder to and much easier to cut to shape than aluminum. (Also, I had a good pile of surplus FR4 material available which is the most important part.) But a friend found a need for the material I had, and with the price of copper shooting up I gave him mine to make his project affordable. So it's back to aluminum for me. But thanks to your project I get to see exactly how PCB plate capacitors will work. You even did the math for me. Thank you.
BTW, the material on your workbench does indeed couple the 2 plates of the capacitor and increase the capacitance value. That's exactly how electronic stud finders work.
I’ve been meaning to make a large air cap for years and haven’t got to it. It would be for a DDRR antenna. My friend made one and uses a vacuum cap (that I can’t afford) and has amazing results with that little antenna. Glad your getting more into hamming around. Keep on tinkering!
TinkerGinger DDRR looks interesting. I’ve never seen that before. I made this cap as an alternative to vacuum variable, as they are expensive as you pointed out. I had the materials on hand, but I’ll bet if I add it up, it’d be cheaper to just buy a vac cap!
@@AmRadPodcast thanks
Nice to see you again.
Thanks! Somehow being stuck at home during C19 has left me with very little time to make videos!
@@AmRadPodcast I want to see more videos on your Elgar AC power source .why you not use and can't see this time on your bench .
Hello Derek, Thanks for the cool video. It's very interesting to see how the math matches the product. I like the way you explain it. Now i have confidence to make my own capacitor for my loop antenna. Greetings, 73's PD0ONE.
That's very fascinating! I never thought to use plated PCBs for capacitors before. Thank you for sharing!
73s AF5CG
Great to see another video from you! I'm in the middle of designing a magloop for my townhouse attic and was considering making a trombone capacitor but I love the idea of using PC boards instead, and you get higher capacitance to boot! Thanks for sharing!
Thanks! I was thinking about this sort of design today--for the same application!--googled to see if anyone did it, and came across your video.
Excellent video..
This is a pretty nice and effective way to make a variable cap. I am also facing the same issue as you are, I built a magloop for 20m a while back. It's capacitor was good for qrp txing but not for 25w+ tx. I was thinking of making a variable cap since they can be expensive and not have enough spacing to not arc at those power levels. Good stuff tho.
Thanks Angel. Definitely add up the cost of materials before committing to a design. I sketched up a butterfly version for water jet and it was expensive - comparable to a vac cap. This project is probably also the same cost as a vac if you consider the linear drive mech.
Top marks, thank you.
Absolutely BEAUTIFUL! Such a fantastic display of the marrige of math, geometry, pyshics and electronics. And it all begins to feel more intuitive. It brings my world of acoustic transmission to life.
Heck yea. I build homebrew mag loops as well
They are good fun!
Well done 👍👍👍
VERY GOOD VIDEO
Nice tutorial on how to make a high voltage capacitor using blank PCBs, something I've wanted to try for some time. I'm interested in a follow up video to see how well it worked in your loop. It's been said by others that PCB caps tend to drift with temperature so I am curious to see if that was true with yours as well.
Thank you.
Subbed to your channel for the LVDT episode. Yeah I don't know whats going on with your subs, I haven't seen any of these videos since then in my feed.
awesome!
Gosh enjoyed I enjoyed vid. I'm.more into crystal radio , low.voltage, but thought you had some good advice atenna
Howdy.
Freckin' awesome !!!
Regards.
This is just wonderful.Question for you Derek or anyone else here. Can something like this be used for old tube style radios? Indoor loop antenna does not really work that good so with variable capacitor what can be applied to me needs? Anyone please comment. Thanks guys, scotty
Great explanation thanks. Did you finish it?
ESD mat is a high resistance from one point to another. Also it should be connected to ground.
Nice capacitor. One could use an old pc cd/dvd rom tray with stepper circuit to move this unit as well.
This is a fantastic idea!
Thanks
Super
what about etching the outer edge away on each single sided board, effectively increasing the air gap without increasing the distance between plates?
Magic that works™
I like it
if i want to make a higher capacity capacitor, aka more pico farrads, whats the approach ? just add more plates and larger surface area ? very nice construction you have !! well done ! im experimenting with resonance ! and looking to atain a use'able variable capacitor with say 0-1000 pf or more. but i think 1000 pf is a good start.
Neat build! Makes me wonder about more compact version using mineral oil, like HV transformers do. It won't be such an eyecandy though if you enclose it in non-transparent way (:
I believe that you can double the voltage handling if doing so (or half distance between plates), but I’d imagine it would be sloppy with leaky shaft seals and such. Mineral oils, transformer oils I believe are flammable too.. I have thought of using EDM dielectric like EDM30, but it’s MESSY. These kinds of oils penetrate everything.
I was thinking of a way to make a vacuum variable somehow. And this is weird, I was just thinking of mineral oil. Just now. So would the oil be better than a vacuum? I would opt for the oil if you are using a stepper motor and contain the motor and plates together.
Copper corrosion when in contact with the air is a consideration. Just a thought what about double sided copper coated PCBs.?
How Can One Would Test Such A Capacitor? Vna? Single Multimeter?
Redo the measurements isolated from ground?
@The Current Source was your second linear actuator just a video slider?
They were both eBay scores from a semiconductor fab clean out. No idea what they were part of.
yeah but you also introduced inductors with the capacitor
parasitic inductance is not an issue at the frequency I'll be operating at
Hello AmRad, I was curious how things went with air variable capacitor for the MLA. I live in an HOA here in Minnesota. I decided to build one for the 11 meter band, although I am currently studying for my amateur radio license. Have you finished your MLA? Thanks for sharing.
It’s pretty much done. I’ll be making a short video on it soon. I’m still playing around with the auto-tuner electronics right now. Keep checking back!
Can you be more specific on the spacers you use? Is it aluminum tube stock? Did you cut these plates? Did you have issues with the shape of the plates when you tested? You got my wheels turning on using PCB board as long as it isn’t too thin of copper.
They’re 1/2” Al non-threaded spacers, had a bunch from another project. I took measurements so far, but haven’t tested full power on the loop yet. Will make a video when I get it all together and stepper control software worked out.
I see a telescope in the background! Do you have any plans to do more astronomy videos?
GreenCoat maybe in the future, but lately I’m thinking about turning it into a satellite tracker.
Did you ever get this hooked up with your magloop?
Still working on the controller, but coming soon
hows that mag loop coming?
Ah, well the loop is collecting dust while I finish a remote stepper controller. The remote driver is working, but the controller is still in the works. Maybe I'll do a video on it as an update. Thanks for the inquiry.
Series LC
If arcing is a problem, why not use a dielectric in between the plates. Polyethylene has a much higher dielectric strength than air, comes in convenient sheets a very low loss tangent and has a relative permittivity of about 2 - wins all the way around. Am I missing something?
Sure you could. You could use transformer oil, you could use sulfur hexaflouride, or a vacuum, or even some kinds of refrigerant. You didn’t miss anything. I had a stack of boards and standoffs, so that’s what I used.
I tried the same design last night, but the antenna doesn't resonate at all. I don't have full devices for analyzing so I need to drop this project
Hmm... I've been using mine for a couple of months now and it works great. How are you feeding it? I'm using a gamma match. If you email me through my website www.thecurrentsource.com, maybe I can assist.
@@AmRadPodcast well thanks, I may do it when I recover from the frustration
Hi Derek,
I saw a video about using aluminum heat sinks as a variable capacitor by meshing the fins. If you use heat sinks with wide spaced fins, could probably make it a HV variable capacitor. Here's a link to the video. czcams.com/video/SB3ewGXekxo/video.html 73 WJ3U
heat/rf =problem. dont touch it its gonna be real hot,
A billionth is 10^ -12
10⁻⁹ I would have thought
@@Ropetangler that is short scale
Very cool method and design 😉 KC3ONO
I think your theory that there are 2 capacitors in series is wrong. Adding a dielectric between air spaced capacitors will always result in a higher capacitance, not a lower one.
There are two dielectrics involved. Air and fiberglass. To calculate the overall dielectric, they must be considered individually and then combined.. as series capacitance. I think I pointed out that the capacitance is higher not lower with FR4. (It isn’t my theory)
@@AmRadPodcast But two capacitances in series are always less than the lower one. So, no.
@@tomtwist1081 That is correct. C1=160pF, C2= 8.54pF and the result is 8.11pF... which is less than the lower one.
@@AmRadPodcast But still the capacitance with a piece of fiberglass in between is higher than that of only air. So you need another formula.
so where is the real test with real electricity?
In the works. Stick around
For butterfly cap build a quick video czcams.com/video/HfTxflu49HY/video.html
Noob! I made a high voltage super capacitor using human beings... top that!
DUDE WHAT HAPPENED TO YOUR HAND DURING EQUATIONS TIME WTF?
Haven’t you seen The Empire Strikes Back?
@@AmRadPodcast , that's so sick.
Great presentation. Many thanks. De G3YPZ
For crap sake, you are inventing the wheel all over again, high voltage variable capacitors are on eBay some of them are vacuum capacitors for 20kV 25pF to 1500pF, what is wrong with you?
I'm not inventing anything. I'm using what I had on hand to make an alternative. You clearly didn't listen to what I had to say in the video. Pay attention. So glad I'm not making these videos anymore so I don't have to listen to armchair quarterbacks put their two cents in every day. Don't like what you see? Go watch someone else.