Love the idea and great execution too Mike. You could design the plates on a PCB system and get them made through the like of PCBWay, 10m boards for a few pound, then use std brass washers to space them. With double sided PCBs and plated holes it could be very interesting.
hopefully i an keep this story short. way back in the day, my Dad called a repair man to look at his TV and radio. The repair man first looked at the radio. I as a baby boy thought wow! there's a city in there! The gang capacitor was like a gothic cathedral. Then the repair man giggled and say to my Dad, here's the problem, and proceeded to pull a tiny deceased mouse that had nibbled it's way into the radio for its new home. And of course shorted out the tube while scurrying around in there. Thanks, your presentation evoked a lot of great memories. Wish you the very best, you and your family. This generation will never realize how wonderfully great those days were before everything changed.
It is important to deburr the edges to reduce arcover. I used to make similar parts on a CNC Punch machine. I would check with local sheet metal shops for a bid. They can make complete parts that are drilled and deburred very quickly.
Ahh, I see you beat me to sharp edges bit already, sorry to have made the point again. Something to be said for reading comments first before shooting my mouth off.
Impressive dedication! I bought an old radio to get the tuning capacitor and germanium diodes and after destroying some of the polystyrene capacitors realised it did not have germanium diodes and was using tube diodes as detectors..............so months later I am slowly getting the radio to work as a restoration project
Nicely done! There's a design I have in mind that's much easier to make. I'll just cut out squares. Drill a hole in one corner for shafts so the square is used as a diamond shape, and nip off the opposite corner to clear the next shaft. I know it's a little unconventional and won't look as cool as semi circles but I'll save a lot of time. Accumulating hardware as I go along.
Nice job for freehand. I spent a lifetime in Aerospace tooling though I am retired now. When you have a lot of identical parts to make, if you can join the individual parts into a larger block you accuracy and speed go way up. If you want to make another tuning condenser after you cut your plates but before trimming to final shape or drilling any holes, you can use double sided tape (very thin) to join all your parts into a block. Now final sanding to shape will go much quicker and the parts will be all the same. When drilling your holes, all the holes will also be the same. If you have even a small hand drill press, that will keep your drill square to your work and a belt sander or disc sander will make final shaping a snap. With better accuracy you can then reduce the gap between the stator and rotor too. Again, very nice job for free hand work!
I think the word you Brits use to describe something fantastic is BRILLANT, so we can go with that. Years ago Crushcraft sold a vertical called an R3 it had some traps for 10,15,20 but also used a capacitor like you just built with a motor and outside box plus it had a control box for inside. I acquired the control box, have a 24-28 volt motor and should have other parts to try to make something work. I also have the driven element from an av4 beam that is about the same as the r3. You make everything seem so easy, but every time I try a project, some hard to find or use tool gets in the way. Trying to build some spreaders for a version of DX Commander the key whole size was not available. You really have a lot of talents !! If you get bored or would like a challenge, I would send you the control box and other parts if you would like to tackle building the outside box, etc to remote tune the antenna. The control box has the voltages etc? Also, the same inside control might be stable with other capacitor tuned antenna like those loops you have built recently?
I seem to remember kits being available to construct variable caps. Hamfest flea markets another good source. Surplus military gear (old stuff) another source for us scroungers.
An interesting project, well done, I may make similar but using double sided PCB for the plates with brass hardware. Watching the test I got the impression your minimum capacitance would be lower if the lower pates were a simple rectangle below the spindle. Not being critical but would make construction a little easier. I do see some companies offer water jet cutting..... might be worth looking into?
Real nice job on the cap. A few years before I bought a commercially made antenna tuner I red necked a tuner together from junk box parts. My coil was the spring which was still in a 5 subject school notebook and the variable cap was from a defunct 9 volt transistor radio. I switched the number of turns on the coil using Rat Shack test jumper wires. You remember those. They had spring loaded alligator clips on each end. Oh, and the 5 subject notebook served as my log book. lol I used it with a 200 watt Swan 400 tube rig and it never arced. My key was a Rat Sheck roller switch - hand held. ((-: Long live CW.
You could have stacked the plates together and secured them in a vice, with some support blocks judiciously placed, before filing them. That way you could get uniformity. Achieving uniformity with the spacers is more critical to making a precision part and also harder to achieve but still doable. It would be best to cut them using an alignment jig though in order to minimize the filing work needed afterwards in order to get them all to be square cut and of the same length.
Very cool. I assumed special materials and exact spacing would be required. I may actually give this a go. I have a very nice variable capacitor that came out of an old ham radio but it's lost in my "collection."
73 Mike, great achievement, but you have to be patient. I was just talking about it this morning with my friend but it will be a 500pf. ps: do not forget to remove the blue plastic which protects the aluminum.
FB OM! I built one this week too, but I used PCB's and switches. It actually went to about 400pf, but I don't think it would handle the higher voltages that yours would. My channel has it if anybody wants to see. But I like yours a lot- very properly built and as good as any much more expensive one, if not better :)
To people looking for a way to make it, and does not have access to all tools, that could be made using raw printed circuit board and a rotatory (?) sand papper. Prefer fenolite (?) pcb over fiber glass. Great job.
All I can think of here is that if I tried half of the stuff you do, they'd call me "Lefty" (with the local hospital getting plenty of my gear money). Fun to watch your craft, Mike...good stuff. 73! de WX0V
That is inspiring! I too have always wished to get a big air gap capacitor. That is a nice simple design. I wonder how large of range one can possibly get with this concept, going big?
Hi Warren, A friend of mine that has a cnc water jet cut all my parts for a very very very big air variable cap lol 900 pf minimum to 1.8 uf max that i put inside a plastic sealed clear box. I use it to tune and find the peak's when i tune the coils of ( Not A BiTT or A BiTT ) The variable 1.5 uf cap is used with other ac caps to get in range and find the peak output of the BiTT or Not A BiTT.. Cheers!!!
Good job because they get an arm and a leg for them these days if you can find them. Although some can be had at a decent price if you look hard enough. 😎👍
Nice job. A belt sander and a drill press might make that a lot easier. Why did you leave the plastic film on the plates? Wondering if it changes the capacitance. I would think it does.
I was wondering that, too. There's no good reason to leave that film on there. It shouldn't change the capacitance too much but it might increase the dieletric losses.
Yes, all you need is a 300 dollar table jigsaw, some high-dollar aluminum plate material, etc., etc., to make your very own variable capacitor!!! Great!
One trick to drill holes from even distance is to drill a clamped stack of roughly cut sheet metal peaces all at once. The final shaping could be done after the drilling then.
It’s a talented piece of work, and VCs are expensive. But, and it’s a big but, looking at the tools you have to own, and the time it takes, not to mention the skill, obviously the skill, I was rather thinking there’s a reason they’re dear.
The protective covering on the "al-you-min-ee-um" as you say, is going to give you a little capacitive bump due to the dielectric effects. Don't know how much (or if it will even be noticeable). I would say that you did an excellent job of achieving your goal for a very high Q cap at a very low cost. What cap value were you shooting for?
Good call. Ebay prices on these things are astronomical. I guess most of those items have long been scrapped or are simply rotting away in sheds or labs.
Looks good! I wonder, with all the work and expense, if it would not have been more effective to have them cut (water jet or laser) professionally - you obviously have the means to draw the CAD files required. That would also benefit from tighter specifications, allowing for smaller plate gap and smaller size for the same range of capacity (unless you are going for an high voltage application).
Hi! Wonderful job you've done! A quick question thought... Isn't going to too lossy for a magnetic loop antenna? It wouldn't be a good idea to weld the plates together to form a one block? The same for the rotor and stator.
There are a number of things that could be done to improve the Q of the capacitor here, but a lower Q might actually be somewhat beneficial in that it would make the normally-stupidly-sharp tuning of a magnetic loop antenna less sharp. It all depends on exactly how poor the Q is, really.
I would like a go at doing this one day but is there any special calculations that need to be done to determing the spacing of each plate for the power used on the radio? I do know that the larger the gap the lower the capacitance will be.
Would Tin Foil from kitchen not work .. Can you please explain why you choose Aluminum ? I understand you may have current requirements , but for a ham radio it should not need that much current.
Foil will burn or pit but it can be used with low power, I used Aluminium because it is malmble and less expensive than Cooper and can withstand high voltages, and when using power of over 50Watts many kV are present.
@@ADVRydrBloke I would start with PLA, it is a lot better to use than PETG, I am finding that the PETG is stringing and needs a lot more work than PLA.... just thought I would let you know
@@mike-M0MSN haha bad as me I had yaesu 767 Gtl DX on the kitchen table apart for over 1 week yer it took me to fix it my wife was very supportive at least she knows where I am lol
Aluminium is know for not making very good conductive connections. Even to let the protective foil on it won't help with this problem. On the other hand - most of this variable capacitors are made from aluminium sheet metal. But with somehow riveted brass spacers, I guess.
You won’t know it’s working if the device receives interference due to the simple face it’s connected to carves aluminum plates. How does the mechanics behind that device have the capability of receiving a radio signal where is the i formation located where I can search and learn about everything pertaining to the research
Open question/observation to anybody reading this. Is the thickness of the aluminum critical? The stock Mike is cutting is obviously too thick to cut with aviation snips but if the aluminum could be thinner, perhaps the parts could be cut from aluminum sheets such as the Alcoa Trim Stock which I think has a nominal thickness of .019" (24 to 25 gauge). The aluminum used in gutters is even thicker. Both of those thicknesses can be easily cut with aviation snips.
congratulations for the channel excellent constructions and above all well done videos ... greetings from Italy IZ8NON Angelo ... I follow you keep it up
@@mike-M0MSN unlikely that you can reach 5kv without carefully treating the edges and 'corners' of the plates. If you look carefully at variables built for transmitting all the edges and corners are rounded. I think you did a FANTASTIC JOB for hand tools and back door step construction.
curious as to why you went with the 2 element style (which requires attaching a wire to a rotating element) instead of the butterfly style where you attach wires to the fixed elements only. Yes the butterfly style has 50% more parts and gives you half the capacitance but it's easy to add more capacitance by making it longer
> "the butterfly style has 50% more parts and gives you half the capacitance " There you go, it's just not worth it because its very easy to get an electrical connection to the rotating part with any flexible wire.
@@nevellgreenough404 Thank you. I found another youtube video that covered the formulas as well (after I posted this question) I also checked my ARRL Handbook 2013, and it was covered in 2.7.2.
