Inductors....

[VK3ZL]

Hi all....These are some of my inductors used for various amplifier and antenna tuners around the place....I hand make these the hard way but the result is satisfactory....Note the two link coupled coils...The large unit is for a balanced tuner 160 to 40 meters...The smaller unit is for 40 meters to 10 meters....These are for coupling into open wire feeders....I send many of these across the world, especially most popular in Europe....I mix this pass time along with my amplifier building.....Keeps this old geezer happy....:)

Bob..VK3ZL..

[WN9HJW]

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[VK3ZL]

I'm interested in how you make those. It's a little hard to tell from the pictures but it almost looks like the support is a piece of acrylic or polycarbonate with holes drilled through it and the wire threaded through the holes? How do you get the turns so nice and circular and even? Is there some kind of form you wind them on? Are they done by hand or is there some kind of machine involved? I

G'day Ron, I usually use 14swg hardened bare copper wire for most inductors, I think that is 12awg in the US.....I calculate the turns/diameter etc of the inductor I want to make and roll out the length of required wire....I use various diameter brass or hard plastic conduit to roll the wire up tightly....There is a knack in this and it is hard on my ancient hands these days....After removing the rolled up wire, it's just like a slinky, I then mark out a piece of acrylic sheet usually .25 inch thickness, and proceed to drill two lines of holes each side to accomodate the wire...Marking the even spacing for the holes, ie 5 turns per inch etc....I then drill the two lines of holes on my drill press using a drill slightly larger than the wire diameter....I have developed a good eye for this and can get the drilled holes very exact....Once the acrylic "card" is finished I then screw the coil on to the former....I next use some spacers through the full length of the coil so that the coil is fairly circular....I generally use poly tubing for this and slide thin strips of old printed circuit board to pack it up firmly.....I then put one end of the card into a vice and starting from the bottom screw the coil up fairly tightly securing both ends....next step is to run epoxy along the windings both sides to secure the windings....When dry I remove the top and bottom packing and you have a perfectly round and evenly spaced coil...I finish the ends securing them with a bolt and solder lug....

One thing you need to remember when marking the card out before drilling....Mark one side of the card first with your spacing starting 3/4 inches from one end...We will call this the top side...Then when you mark the bottom side of the card allow 3/4 inch plus half the top spacing to get the correct coil pitch...This is important or the coil will look funny....

Hope this is of value to you and others...Sounds complicated but I can build half a dozen inductors by hand in one morning....

Bob..VK3ZL..

[WN9HJW]

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[N5RLR]

Excellent work, Bob.

[kd8dey]

I've been wanting to do a 240uh spider coil but dunno the formula needed for the inductance.
I'm pretty sure that it's not the same as the one used for a single layer coil

[N4VGB]

Hi all....These are some of my inductors used for various amplifier and antenna tuners around the place....

I send many of these across the world, especially most popular in Europe....

I wondered where the guy at most of our local hamfests was procuring those cols.

[KG4CGC]

I'm very jealous!

[WØTKX]

Good coily stuff. Tell us more about adventures with balanced tuners, there in the land of serious QRO.

[N8YX]

Got access to any silver-plated 12 or 14ga wire? Build one out of that and test in one of your amps.

Be curious to see how amplifier stability changes when the two types of coils are swapped back and forth.

ETA: I think Corey was inquiring about building one's own air-variable capacitors. Think there would be sufficient interest in a remote-controlled auto-tuner using motor drives on the caps and a stepper-type rotary switch for selecting coil taps?

If so, I'd be willing to write the firmware for the controller end of things.