# capacitance of this inductor

Discussion in 'Electronic Design' started by Gary Peek, Sep 15, 2006.

1. ### Gary PeekGuest

I have found the following series of coils to be a dandy
alternative to winding your own coil when playing around
with FM wireless microphone projects:

http://www.mouser.com/catalog/specsheets/XC-600155.pdf

The data sheet does not suggest a capacitance value.
Anybody care to take a guess? (It's not critical, I'm
just wondering.)

Gary Peek
Industrologic, Inc.

2. ### Michael A. TerrellGuest

Can't you figure it out for yourself? its a simple resonant circuit.
Subtract the minimum inductance for a given coil from the maximum, and
divide it in half to allow for some tuning range, then use that value
and the desired frequency to calculate the required capacitance.

There are eight different coils and 100 US FM channels
expect someone to give you all 800 answers, do you?

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

3. ### Winfield HillGuest

Gary Peek wrote...
Those are fine, as far as they go, but it's not far, only
to 0.465uH. That's a rather limited HF operating region.
Taking the 0.465uH inductor, they don't give the SRF,
which many inductor manufaturers provide, but they do
test at 50MHz. So if we assume an SRF above 100MHz,
that limits the coil's self-capacitance to 5.4pF.

4. ### John WoodgateGuest

I think he wants the self-capacitance. Only the manufacture or a user
would know that, and it SHOULD be on the data sheet.

But if the coils are good to 500 MHz, the self-resonance must be higher
than that, so, taking the maximum inductance, find the capacitor that
resonates at 500 MHz. The self-capacitance must be less than that.

5. ### Gary PeekGuest

Thank you John, you indeed understand the question, and thank you
Winfield, since you gave me the quick estimate I was interested in
and how to find it. I too agree it should be on the data sheet.

Gary Peek

6. ### Guest

Bit late maybe but for a bare wire single layer solenoid ...

Coil capacitance = radius in centimetres.

If wire is insulated or moulded in plastic then double the value.
john