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 Shorting wafer switch 
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Post Shorting wafer switch
I am building a version of the Annecke link coupled balanced ATU. I've got most of the parts now but am stuck with the bandswitch. This switch is a wafer switch which shorts out the unused turns on the ends of the main coil. Some many years ago I remember reading an article (probably in QST) on how to wire up two wafers to act as a shorting switch. Alternatively, does anyone know where I might obtain 2 shorting ceramic wafers? Any help or suggestions welcomed. Many thanks.
73 de Ken G3RFH


Thu Nov 29, 2018 10:08 am
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 Shorting wafer switch 
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Post Re: Shorting wafer switch
Ken, I know exactly what you mean, but I think you might be hard pushed to find such an animal. I have always used a normal 10 way single pole switch and shorted the unused turns out like that, never had a problem.

These days I've moved away from trying to get ceramic switches in favour of 4mm plugs and sockets, they are cheap and in plentiful supply.

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Thu Nov 29, 2018 10:28 am
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 Shorting wafer switch 
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Thanks Paul, but I think I've got it now.
Get 2 wafers, wafer 1 has all its contacts (except the pole) wired together. The pole is connected to the pole of wafer 2 and the contacts of wafer 2 go to the taps on the coil. The end of the coil is connected to wafer 1 joined up contacts. Repeat for the other end of the coil. I won't know if it will work till I've built the atu but in my head it works!!
Surplus Sales of Nebraska have ceramic wafers starting at 45 US dollars!!
So into the junk box. I've got several ceramic wafers so no problem.
73 de Ken G3RFH


Fri Nov 30, 2018 10:08 am
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 Shorting wafer switch 
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$45 plus the handling charge and VAT they are expensive.

It sounds like youv'e got it sussed, OK if you are flush with wafers.

It sounds like and interesting project, good luck with it.

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Fri Nov 30, 2018 10:37 am
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 Shorting wafer switch 
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Post Re: Shorting wafer switch
I bought some very nice ceramic wafer switches from Russia a few years back, not expensive and beautiful quality.
Have to look on ebay.com not ebay uk if they are still available.

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Fri Nov 30, 2018 10:53 am
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 Shorting wafer switch 
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Post Re: Shorting wafer switch
I have enough wafers for this project but I'll have a look for those Russian ones.
On the subject of rare parts, I've often wondered why nobody in China or Russia makes roller coaster coils at a reasonable price. The only ones I have found are made by MFJ but the freight charges from US make them very expensive.
Thanks for your comments.
73 de Ken G3RFH


Sat Dec 01, 2018 10:15 am
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 Shorting wafer switch 
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You have to be careful of buying "ceramic" switches from China because I bought some and they look ceramic, but they are not, they are some type of plastic, they are OK for low voltage RF but I wouldn't like to use them on the high voltage part of an ATU.

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Sat Dec 01, 2018 12:36 pm
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 Shorting wafer switch 
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Post Re: Shorting wafer switch
Probably similiar to some I've seen in America made of 'steatite' whatever that is.
Ken G3RFH


Sat Dec 01, 2018 1:53 pm
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 Shorting wafer switch 
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I must admit I had never heard of "steatite", so I looked up the definition.
Two sprang up, one for the actual substance, the other for a modern day common use of it:
Quote:
Steatite:
1: The mineral talc occurring in consolidated form, especially as soapstone.
2: An electrically insulating porcelain composed largely of steatite.

Well there you go, something else I have learned! :)

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Sun Dec 02, 2018 12:37 am
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 Shorting wafer switch 
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Post Re: Shorting wafer switch
Education is a wonderful thing.
So its as good as ceramic then, I'll remember that.
73 de Ken G3RFH


Sun Dec 02, 2018 10:25 am
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 Shorting wafer switch 
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Post Re: Shorting wafer switch
It's certainly not a plastic, like you get in some of the cheap Chinese stuff.
I have one of those offerings here, the insulating wafers holding "disc" is a "soapy" feeling relatively soft plastic, either nylon, or PTF based, or a combination of both?
That Steatite stuff, is apparently a hard fired type of ceramic.

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Dave G0BHD.


Sun Dec 02, 2018 10:30 am
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