I carried out a series of tests on Rayners formula for inductors a few years
ago, making up single layer coils between 20nH to 1mH and measuring them. All
were within 20% of design, and most of the values above 200nH accurate to
within to 10%.
Both my 73 and 137kHz loading coils were within 5% of design value (that is
actual real inductance, not the effective value after taking distributed
capacitance into account)
Initial design of multi layer coils is not too far out with this formula
either.
L (uH) = (N.D)^2 / (0.46 D + 1.02 G)
All dimensions in mm, D is coil diameter, G is length, N number of turns.
Andy G4JNT
-----Original Message-----
From: Hugh M0WYE [SMTP:[email protected]]
Sent: 2003/02/06 16:13
To: [email protected]
Subject: LF: Re: "Decca-type" coils
Hi Peter
Hello lf-group,
is there any formula to calculate a loading-coil like the Decca-type?
Abt 3 mH might be required.
By "Decca-type" I presume you mean "basket weave"
Alan Melia has pictures and some design info for a home made basket weave
coil of 2.3mH and another of 9mH at
http://www.alan.melia.btinternet.co.uk/lfaecoil.htm#LF%20Aerials%20and%20Loa
ding%20coils
I find coil equations rarely give an accurate value of mH, I prefer to wind
some turns and measure the resonant frequency with a capacitor of known
value. Then add or subtract turns until the desired value is obtained.
Hugh M0WYE
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