HAM RADIO: Building a Variable Capacitor, Butterfly and Two Plate DIY Capacitor, Magnetic Loop

[@Kangsteri]

Good work. You get less interruption on the signal if you use the moving side for ground. Also a long stick or some lanyard system further away from the cap makes it easier to adjust, without hands creating more capacity near it.

[@apburner]

You have made effectively what is called a Belleville washer. Brilliant idea.

[@mike-M0MSN]

Thank you!

[@noneyabusiness969]

Here's a suggestion, Try adding a little bit of nolox in between the "spring" washers, the eye terminal, and shaft so it will be corrosion-resistant and maintain better conductivity over the life of ghe cap... great build info!

[@mike-M0MSN]

Great tip!

[@M0RMY]

Mike - those are absolutely brilliant. I really like the kitchen/engineering fusion and great video edits. Now we need to see them in action!!

[@mike-M0MSN]

Hi Tom, what build as well as use them, cake and eat it. No no no.. well maybe 🤔👍🤪

[@macgyver5108]

Two ideas instead of using the slip ring: Measure the diameter of the shaft and find a stainless steel RC car type bearing or perhaps a skateboard bearing (Amazon or a hobby shop) with the correct inner diameter. Then make two more narrow spacers out of tubing like you did for between the cap plates and sandwich the bearing between those so they tighten down on only the middle bearing shaft. Then look up how to solder onto stainless steel and solder your electrical connection wire to the outer ring of the bearing, there's a specific type of flux needed too but I don't recall at the moment... THAT, or even simpler: use a long and flat strip of brass sort of like a "leaf spring" so that it rides on one of the shaft spacers with a bit of tension. Drill a hole or two on one end of the brass strip, make sure it has the right amount of bend in it for tension, screw it down and solder a lead onto it.

[@lectrikdog]

bent washers are made with spring steel, they'll work better than bending a regular one.

[@JoseSilveira-newhandleforYT]

As I remember from my RF adventures in my teens, the outer body of the capacitor is metal and in contact with the moving plates (usually would stay at chassis ground), and the static bank(s) of plates are isolated from the body, with solder pegs attached. This overcomes the need for slip rings or similar wear prone parts. Of course, it's harder to make the body of the capacitor in metal, than just 3D print it :-)

[@philtuckerm0dpk212]

Great work. So interesting.

[@mike-M0MSN]

Many thanks!

[@n4zou]

I've built capacitors like that except I used thin copper sheet metal and copper tubing plumbing pipe for spacers. The end peaces and base were cut from lexan sheet plastic and bent with heat. I used all thread for that fit inside the copper tubing. I used aircraft tin snips to cut the copper sheet I used. The copper part's end up deformed slightly but can be made flat by pressing between thick wood boards and C-clamps to exert pressure on the parts. To greatly improve the capacitor the copper part's can be silver plated, which you can do yourself. There are lots of youtube videos of that.

[@mike-M0MSN]

Sounds great, I will have to give that a go.. :)

[@scharkalvin]

Thread a nut on BEFORE you cut the rod, and then unscrew the nut which will act as a die and 'fix' any broken threads. Instead of a sliding contact, attach a short bit of coax braid to the capacitor shaft and screw the free end of the braid to a post on the rear of the capacitor for connection to the circuit. The braid should be just long enough to allow the capacitor to rotate 180 degrees. You could have 3D printed that knob with a hex hole in the middle for the nut. That drill makes conical holes (thicker on one side than the other)! Not only is the butterfly cap easier to build, but it will work better on a magnetic loop antenna as it is balanced. But you will need 4 times as many plates since it is now two capacitors in series, and the plates are half the size of the conventional capacitor.

[@mike-M0MSN]

Yep, that why I made the trombone Caps...

[@Joe-KN4IFI]

Looking good Mike. 73 Joe

[@mike-M0MSN]

Thanks

[@ianxfs]

Or toast rack? 🍞👀 Nice job Mike 👍🏻 I put nuts on before cutting bolts/bar, as undoing the nut makes good any bent thread. Two locked nuts also give you a flat edge to cut across if using junior hack saw 😀

[@mike-M0MSN]

Brilliant Ian, great idea.👍😀

[@James_Bowie]

Yep, old trick that one.

[@glenmartin2437]

Thank you.

[@mike-M0MSN]

You're welcome!

[@ukm6yik69]

Splendid job Mike. Can't wait till my builds are as good as yours. Great work as always :)

[@mike-M0MSN]

Thanks again!

[@EMNM22]

Just use a spring and washers. The spring gives the washers enough constant pressure to make contact.

[@ZL1BQDRoly]

Remind me to send you some photos of how the commercial guys connect the rotary vanes for the BIG variable caps we use..... cheers

[@BoB4jjjjs]

Make a video of it.

[@mike-M0MSN]

Hey Roly, must catch up sometime.. cheers

[@brendanhynes473]

many thanks for the video Mike very informative an useful de GM0CQV

[@mike-M0MSN]

Very welcome

[@DonDegidio]

Hi Mike, Don't know how well stocked the hardware stores are over there, but if you can locate a large diameter brass washer capture it between two nuts and make a wiper for it. I think it will work better than the bent flat washers and ring terminal. Sta safe. 73 WJ3U

[@mike-M0MSN]

Great Idea Don, I will see what I can find.👍

[@Christophers-Assorted-Stuff]

I only just found this video after looking for variable caps on ebay. I don't understand why you made the spindle connection in that way. My method would be to use a springy brass strip fixed to the end plate with a couple of small screws and nuts. The strip would be bent to contact the end of the spindle and the other end would be bent out like a solder tag. That allows for a good fixing of the spindle without the possibility of the wire connection ever moving.

[@mike-M0MSN]

good idea.

[@2EOGIY]

There is no need for a slip ring if you divide static plates into two parts with an insulator (i.e. half of plates have nylon washers on the left one threaded rod and the other half on the right one. You might want to fill the gap between plates and rods with some small gaskets).

[@iestynwyn4311]

brilliant mike aka face....

[@mike-M0MSN]

Face.... lol

[@petereverett1455]

You might be onto something with the banana slicer. If I ever need to insert a nut into a 3D printed part, I heat it on the top of the soldering and use the iron to push it in. I found it a bit easier (but slower) than the blowtorch/gas hob method.

[@mike-M0MSN]

Cool idea

[@VASGENR6DJF]

good/ like

[@markg6jvy135]

👍👏👏

[@gpcitnc]

A thought the slip ring, what is the maximum rotations of the capacitor? I would expect less than one. If this is the case, simply put the electrical connector between two nuts and sock them down, if need be, add another nut to better lock it.

[@transmittinguntilrobotsrep1045]

Excellent video, thank you for putting these out for the community! de AC3DS

[@mike-M0MSN]

You are welcome.

[@LanceVK6LK_AussieHam]

Rather than a slip ring, why not use earth braid. It can flex/move and not be damaged therefore you can tightly fix it to the centre with two nuts.

[@joecraft4409]

You could have used a short spring to use to keep pressure on the ring terminal to the allthread shaft. Or a curved washer ! 😂

[@tommylee7218]

Pro trick: you can watch series at Flixzone. I've been using it for watching a lot of movies during the lockdown.

[@orionjaziel7342]

@Tommy Lee yea, been watching on Flixzone} for years myself :D

[@mikegLXIVMM]

Looks great! What kind of circuit will it be used in?

[@mike-M0MSN]

going to use it on a mag loop

[@ivand8393]

I like you assessment "relatively well" and "middle-ish" :-) Are you going to share some measurements C = F(angle) especially for the butterfly ? And probably the contact resistance of the slipping wiper end during few rotations ?

[@mike-M0MSN]

Stop the Video at the drawing of the capacitor and copy info from that. :)

[@ivand8393]

@@mike-M0MSN thanks for the suggestion, but actually I mean how good is the electrical contact during the rotation of the thread ? And I am wondering what is change of the capacitance per one (or couple) degree of rotation ? Is it "relatively" constant (in other words with this shape of the pates, is the relation "capacitance/angle of turning the knob" linear ?

[@martinhoward9812]

Great video Mike, why don't you use a spring from an old cloths peg as a spring for the pressure plate.

[@mike-M0MSN]

Idea :)

[@GateKommand]

Good build mate, will you be knocking up a thermionic valve next :)

[@mike-M0MSN]

lol

[@MW6PNW]

Great job Mike. Is there a requirement In mm for the plates to pass or is it just make sure they clear each other?

[@mike-M0MSN]

The more MM apart the high voltage the cap can handle but the lower the capacity, so it’s a balancing act.

[@KenPowellG0PPM]

split stator variable capacitor

[@pulponair]

Hey Mike - great video as alwasy. Could you please measure initial capacity on PLA vs PETG? (Maybe even ABS or ASA if you can).

[@mike-M0MSN]

maybe when I make a new one with the PLA

[@problemwithauthority]

Hi Mike. Nice work. What type of mag loop are you planning?

[@mike-M0MSN]

I have made them to go on the twin copper loop to see if I can run twin Capacitors. 🤪

[@problemwithauthority]

@@mike-M0MSN I tried a mag loop once and found that I needed to be a few feet away because I was part of the capacitor. I added a plastic pipe to the capacitor shaft to keep me out of the way. Also found out the antenna didn't work well inside the house with aluminum siding.

[@SuburbanDXing]

Mike, another interesting build and I enjoyed it, however, I had 4 ad interruptions in a video that ran less than 12 minutes. I'm not against monetization, but the ads hurt my enjoyment of what was otherwise, another solid M0MSN video. One or two ad interruptions are fine, but 4 was too many. Just being honest here. Thank you for posting and keep up the very interesting work. 73! de WX0V

[@mike-M0MSN]

I wish I had control over this, it is my understanding that YT now push ad’s over just about every upload, however I will put my hands up and admit not checking the mid roll button on this upload, which is something I would have normally done, so maybe that’s why apologies.

[@SuburbanDXing]

@@mike-M0MSN Well, ads or not, I still love your material (one of my favorite You Tube channels). If I didn't, I would have not said anything. Thanks for your efforts here...73! de WX0V

[@mike-M0MSN]

@@SuburbanDXing thanks 🤩

[@anonymousguy144]

Do you know where i can get the aluminium plate

[@jeremycole3008]

you have come this far, why not build the general-radio-company's butterfly resonator that they used in their oscillators from the 1950s ?

[@Justin-bd2dg]

Screw those disks, they are dangerous! Only use the fiber reinforced!

[@inoxat49]

Mike. Hope you don't mind me asking how long does it take your 3D printer to print those Variable Capacitor end plates. They look good.

[@mike-M0MSN]

A bloody long time... LOL

[@EngineeringVignettes]

What capacitance range are you trying to target, or another way of asking, what frequency range (or band) are you targeting ? It seems like the current prototypes would only be effective in the 10m band area? Cheers,

[@mike-M0MSN]

Not so, you only need a small capacitor if you intend to use it on a loop, that's sitting on the band you want or you couple it with a fix cap... its all fun.. :)

[@EngineeringVignettes]

@@mike-M0MSN Thanks,yes the use of fixed caps can help.. depends on the freq range coverage... It make make a good band spreader as well. Cheers,

[@tomcren59]

A Belleville washer is a conical spring washer. It is designed to be a spring and will not fatigue over time like a simple washer bent. en.wikipedia.org/wiki/Belleville_washer

[@mike-M0MSN]

Yep, but I would have to purchase them.. :)

[@藤井司-o9t]

Can you please announce the thickness of the aluminum plate used for this variable capacitor and the cut size?

[@mike-M0MSN]

1.2mm 80mmx40mm

[@stanholmes4293]

Hi Mike Can you provide additional information on the dimensions. The stator plates are moved out by to what radius? What is the spacing between plates? What is the Min and Max pF and number of plates used? Regards Stan

[@mike-M0MSN]

sorry Stan, It's about trying for yourself, what I make may not work for you.

[@BoB4jjjjs]

That yellow one looks a ream mean machine, but its a capacitor! Looks like some sort of torture equipment!!! EDIT: What is wrong with this keyboard, I press Caps and it does not do it. Much worse, it can't spell lol.

[@mike-M0MSN]

hHEE. Same Problem lol

[@kevinkc3onohelijeepworld953]

Nice what cap range do each design give ? Thank you KC3ONO

[@mike-M0MSN]

Well that’s the beauty of building your own you can add plates until your get what you need, these are 300pF (butterfly) and 150pF toast rack

[@kevinkc3onohelijeepworld953]

@@mike-M0MSN so true thank you for the specs 😉☺️KC3ONO

[@glynhicks4762]

Hi have you got the STL files for the end pieces please

[@mike-M0MSN]

Hi Glyn, sorry where's the fun in that, besides you need to make them to fit the capacitor plates.

[@patprop74]

What's the picofarad range?

[@mike-M0MSN]

15 to 120pF