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Old 26th Nov 2017, 10:57 pm   #5
G0HZU_JMR
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Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 3,077
Default Re: Directional coupler DC - 300 Mhz

It looks like a classic Sontheimer coupler (patented in 1966?)

The coupling factor is 20*log(N) where N is the turns ratio. So if there are 6 turns on the secondary and the primary just passes through the twin hole bead once then the coupling will be about 15.5dB.

These things often work over a decade or two of bandwidth although you usually only get good directivity over a decade or so. But a lot depends on the ferrite material used. Does your ferrite have any colour markings? eg a hint of purple for example?
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Last edited by G0HZU_JMR; 26th Nov 2017 at 11:17 pm.
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