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Locked Homebrew Butterfly capacitor, 12,000 volts!
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n4zou
I just finished a project I have been working on the last few weeks.
A large Butterfly capacitor for my soon to be built 20 and 40 meter transmitting type Magloop. It is 10-pF minimum and 100 pF maximum with spacing for 12,000 volts. It is made from 15 gauge copper sheet metal, 1/4-20 all thread, 1/4-20 nuts, and Plexiglas. I used aviation snips to cut the copper, a drill press for the holes and a skill saw for the Plexiglas. Testing on another 20 and 40-meter loop requires 17-pF at 14.350 and 91-pF at 7.0 MHz. The loop will also work on 30 meters as well. I just uploaded photos of the capacitor in the photo section. Just click on the N4ZOU folder. The old test loop used RG-8 coax as the element and a split stator capacitor. You had to add a second capacitor to get it to work on 40 meters. This new setup will use 3/4 inch copper pipe for the element and will have continuous coverage between 14.350 and 7 MHz. |
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furman2020
Please post pictures and diagrams of your new loop
and butterfly cap. I am very interested in building the same thing, except mabe for 80 & 160. Also, please give us details on the performance of your new loop system, compared to dipole or vertical if possible. Thanks. Furman2020 K5QA --- In loopantennas@..., "n4zou" <n4zou@y...> wrote: weeks. A large Butterfly capacitor for my soon to be built 20 and 40meter transmitting type Magloop. It is 10-pF minimum and 100 pF maximumsheet metal, 1/4-20 all thread, 1/4-20 nuts, and Plexiglas. I usedaviation snips to cut the copper, a drill press for the holes and a skillsaw for the Plexiglas. Testing on another 20 and 40-meter looprequires 17-pF at 14.350 and 91-pF at 7.0 MHz. The loop will also work on30 meters as well. I just uploaded photos of the capacitor in thephoto section. Just click on the N4ZOU folder. The old test loop used RG-8 coax as the element and a split stator capacitor. You had to add awill use 3/4 inch copper pipe for the element and will have continuous |
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Scott Erwin
I already have a photo of the capacitor uploaded in
the photo section as stated in the original post. Here is a web page that details how to build your on capacitors. It takes some time for all the pictures to load. The drawings for the stator, rotor, and endplates are all in metric. I made my capacitor slightly larger to allow using 1/4-inch hardware. 6 mm is close but slightly smaller and the 1/4-20 nuts would have extended out past the stator vanes slightly and I did not want it looking like that. Here is a direct link to the photo of my homebrew capacitor; I hope it works anyway hi! My test loop was made from RG-8 coax used as the element and an old split stator capacitor. It was everything you did not want to do in building one! Small diameter and high loss in the element as it's not a solid conductor and the capacitor was not welded across the top of the rotor. I still made contacts on it! The new Magloop is going to be built without the built-in losses of the test or fold up portable loop but will still transport nicely in the pickup bed of my truck. --- furman2020 <k5qa@...> wrote:
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I just took a moment to look at your great work on this butterfly
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capacitor. I'm curious if you could give an estimate on what your materials cost were. I'm trying to determine if this is the route I should take - or if I should acquire one of MFJ's butterfly capacitors (just recently advertised in the latest MFJ catalog for ~ $70 along with their two new 'loop' tuners). - Daniel / AA0NI (normal disclaimer - no affiliation with MFJ - just happen to own one of their Antenna Analyzers) --- In loopantennas@..., "n4zou" <n4zou@y...> wrote:
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n4zou
I got the copper sheet metal at a local sheet metal shop. It was 4
3/4 inches wide by 8 feet long and I used 5 feet of it for my capacitor. I gave $6 for it. It was in a rack with other bits and peaces of sheet metal that was large enough not to put in the scrap copper drum to be sold as scrap. The owner likes to sell these bits and pieces to people (like me) that are not big enough to use for contracted jobs. Look in your telephone directory for sheet metal shops and ask if they have copper or aluminum scrap suitable for your use that they will sell to you. Basically; I had a scrounge fest in this sheet metal shop! I also bought some aluminum sheet and made an enclosure for the control box as well and he even cut and bent the aluminum sheet for me. The hardware used was a 3 foot long peace of steel 1/4-20 all thread rod for 99 cents and 100 1/4-20 nuts in a package for $3.89. The hardware store also had a small sheet of Plexiglas in there "left over bin" that was just large enough to make the end plates for 25 cents. Back a several months ago I did email MFJ if they would sell me just the capacitor used for there Magloop antennas and got an answer back that they were not set up to do that but told me it was a good idea as they could not ship a large Magloop that would work below 30 meters. I guess some other people asked the same question and now they're doing it! $70 bucks for a MFJ capacitor made for a Magloop is not a bad price at all! I had plenty of time to hand craft my capacitor and having had major brain surgery a few months ago I am now in home therapy to try and recover from some of the disabilities I have now. The therapy people wanted me to do some dumb craft items so I had my Wife drive me around to get the stuff for my capacitor craft item. They looked at me strange when I showed them my capacitor instead of a decorated paper holder. ;<) If I was still working a job I would have just bought the MFJ capacitor if it had been available at the time. --- In loopantennas@..., aa0ni@y... wrote: cost were. I'm trying to determine if this is the route I should take -or if I should acquire one of MFJ's butterfly capacitors (just recentlyone of their Antenna Analyzers)weeks. meterA large Butterfly capacitor for my soon to be built 20 and 40 sheettransmitting type Magloop. It is 10-pF minimum and 100 pF maximum aviationmetal, 1/4-20 all thread, 1/4-20 nuts, and Plexiglas. I used sawsnips to cut the copper, a drill press for the holes and a skill requiresfor the Plexiglas. Testing on another 20 and 40-meter loop 3017-pF at 14.350 and 91-pF at 7.0 MHz. The loop will also work on photometers as well. I just uploaded photos of the capacitor in the RG-8section. Just click on the N4ZOU folder. The old test loop used acoax as the element and a split stator capacitor. You had to add willsecond capacitor to get it to work on 40 meters. This new setup use 3/4 inch copper pipe for the element and will have continuous |
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I can build for u any air variable capacitors |
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Craig F. Simmons
What is the lowest capacitance on one of your kits, along with the max. I keep seeing the highest being listed but nothing about the low end. This is important to me because I have one loop that works great on 30 meters and 40 meters but just lacks a going low enough to cover it. Both valuse would be great to know if possible. And yes I know if I make the loop length shorter that will change what is needed.? This will make it easy for me to order a few kits. thank you Date: Thu, Jan 30, 2014 at 7:49 AM Subject: Re: [loopantennas] Re: Homebrew Butterfly capacitor, 12,000 volts! To: loopantennas@...
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I can build for u any air variable capacitors |
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Craig F. Simmons
Date: Thu, Jan 30, 2014 at 10:33 AM Subject: Fwd: [loopantennas] Re: Homebrew Butterfly capacitor, 12,000 volts! To: loopantennas@... What is the lowest capacitance on one of your kits, along with the max. I keep seeing the highest being listed but nothing about the low end. This is important to me because I have one loop that works great on 30 meters and 40 meters but just lacks a going low enough to cover 20 meters. Have minimum and maximum would help to calculate what length and size material will work. Both values would be great to know if possible. And yes I know if I make the loop length shorter that will change what is needed.? This will make it easy for me to order a few kits. thank you Date: Thu, Jan 30, 2014 at 7:49 AM
Subject: Re: [loopantennas] Re: Homebrew Butterfly capacitor, 12,000 volts! To: loopantennas@...
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I can build for u any air variable capacitors |
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You might want to email him directly.
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That is a very good question, BTW. Steve Greenfield AE7HD --- In loopantennas@..., "Craig F. Simmons" <k910dog@...> wrote:
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Steven Greenfield AE7HD
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