Welcome to the spider form calculator

This form will help you design a contra-wound spider (spiral) coil to match a variable capacitor

Thanks are due to Dave Schmarder and Mike Peebles for helping me to debug and test this page, and to Ben Tongue for the original concept.
I hope you find this page useful!
Jeff Welty, Febuary 2007

Step 1.

Enter your values below, then click the "Submit Query" button


Minimum pf value of your variable cap
Maximum pf value of your variable cap
pf value of your trimmer variable cap (or 0 if no trimmer)
pf value of "extra" circuit capacitance
Wire pitch (inches)
Hub diameter (inches)
Minimum Freqency Khz (use 520 for AM band)
 
Some pitches for wire gauges
Gauge (AWG) Diameter (inches)
160.05080
180.04032
200.03200
220.02540
240.02016
260.01600
280.01270
300.01008
Some pitches for litz wire
Strands/awg Diameter (inches)
660/460.048
330/460.032
165/460.024
100/460.0175
40/440.01275