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LF: Re: Capacitance switch box design - what is the simplest?

To: <[email protected]>
Subject: LF: Re: Capacitance switch box design - what is the simplest?
From: "Martin Evans" <[email protected]>
Date: Sun, 16 Jan 2011 15:32:50 -0000
References: <[email protected]>
Reply-to: [email protected]
Sender: [email protected]

across the capacitance can be very many times larger than that at 50 ohms.

So, I need *to build a capacitance selection box with values from around
0-30nF with sufficient resolution to fine tune a hi-Q loop*. I will need the
capacitors to be rated sufficiently high voltage to cope with any power
level I am likely to put into the loop antenna (almost certainly never more
than 20-30W though).

My questions are these:

(a) what is the best *choice of capacitors* - type, voltage working, pulse
behaviour, accuracy, price?
(b) what is the *simplest arrangement* to give me the adjustment accuracy
and range I need with the fewest parts and fewest switches?

Any advice would be appreciated.

73s
Roger G3XBM


Well, to do 1nF to 30nF in 1nF steps, you need six caps and six switches -

1, 2, 2, 5, 10, 10nf caps

all in parallel,  with a (toggle?) switch in series with each capacitor.

Martin GW3UCJ.




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