P
Phil Hobbs
- Jan 1, 1970
- 0
Jim said:I duplicated a miniature bird telemetry transmitter from an existing design,
and would like to replace the 2 wound coils in my next one with available
dipped through hole, or even surface mount inductors
The coils are:
12 turns #36 wire 1/8"dia. (this has a 22pf capacitor in parallel in the
design with the antenna wire on one end)
4 turns #32 wire 1/8" dia.
Is this enough information that someone can give me the values I need to
order as replacements?
Thanks
Jim
If they're air core, it's pretty easy: To an accuracy of about 1%, the
inductance in microhenries of an air-core coil is given by the formula:
L = a**2 n**2
-----------
9*a + 10*b
where
a is the radius of the coil in inches
b is the length of the coil in inches
n is the number of turns.
Note that it's easy to get the turns count too low by 1/2 or 1 turn: a
hairpin counts as 1 turn. Also this formula works best for coils with
many turns.
Cheers,
Phil Hobbs