[amsat-bb] How you wind it

[Robert Bruninga]

How you wind a coil makes a BIG difference.

Ever wonder why your projects don’t work like the authors?



Im winding 42 turns onto a 1 Megohm 1/4W resistor to make a loading coil to
make a 5’ whip antenna on a cubesat tune to 28 MHz.

I was getting nowhere trying to add and subtract turns.  With a bandwidth
of only 200 kHz it was inconsistent getting to 28.120 center freq.



Then I simply took the same length of wire and tried 3 methods all with the
same number of turns.



1, down-and-back-and forward for 3 layers = 24.5 MHz

2, left-to-right but scrambled 3 layers along the way = 30.0 MHz

3, just a little squeezing of turns that had loosend = 28.8 MHz



Wow, just changing the winding method moves the 0.2 MHz bandwidth as far as
30-to-1!



The difference of course is the stray capacitance between the end turns.

So winding method is important!



Just thought I’d share the results…



Bob, WB4APR