Making the tie points for the coil

As you can see the loops are on the fiber glass rod. You could simply solder the lead wires to the wires and leave the rod but the single turn loops would be hard to keep from shorting out.

I simple took my needle nose pliers and put a little twist in each loop. I staggered the single turn taps to make it easier to connect to them without shorting them out.
If you want to avoid the soldering you can make the loops about 5 or 6 inches long and twist them at each point as you wind the coil. This will work but you will have a lot of tags to keep up with while winding the coil.

winding a 20 tap coil

The switch on the left is the units selector and the one on the right is the tens. They are able to select from 10 to 109 turns a single turn at a time.As you can see I have an armature on the left hand switch. when I cut the bar I will make another for the right hand switch.

I put a little glue around the contacts on the bottom to help harden the board and seal moisture out. The screw has a terminal lug and spring to maintain contact while allowing the switch to turn without the wire twisting with it.

When it is wired I will have 10 turns with both switches in the center position. Moving the units switch CCW will increase the turns to 19. Moving the tens switch one click CW will give 29. Rotating the units switch CW will produce 20 turns. And so it goes. We can have 10 turns to 109 turns.

I used a paper towel core and a 1/4" fiber glass rod to wind the coil. You could use a pen or pencil with a straight shank. I simple wound 10 turns around the core and rod then nine on the core one on the core and rod etc. I pushed the wire under the rod with my thumb and put some Q-dope on the coil. After the dope cures I'll remove the rod and twist the loops to make a place for my connections.

Note: If you have no Q-dope use clear finger nail overcoat or varnish.

Browning-Drake

Browning drake

A screen shot of the cover of the magazine linked above.

avalanche and tunnel effect in semi conductors

Mr Polyakov explains this in his book "Semi Conductors made simple". If you read the book it may help with semiconductor theory. If you know the basics and just have the specific question page 95 is a good place to look for your answer. The book is here:

Polyakov - Semiconductors made simple

making Q-Dope

If you have deep pockets you can just buy some for about $5 an ounce accept the health risk and skip the rest of the post. Otherwise you can make it for about $3 a half pint.This is what you need.

 100% acetone nail polish remover 1$.

 Ping pong balls about a quarter each.

Cut up the balls and put them in a glass container. Add acetone to the glass container. (do not use a plastic container unless you know it is acetone resistant.) The bottle the acetone came in will work after you use some and make room for the balls. Let it sit over night and you have this white glue. I use one ball per ounce of acetone and have good results.
Basically this is liquid celluloid. You can use it to make coil forms and as Q-Dope.
I wrapped a paper towel around a paper tube and coated it with the dope. After two or three coats I have the form for my next coil.
I have used the Q-Dope and it is good stuff BUT it is MEK based. Many years ago MEK was banded from my work place as a health hazard. The home brew using acetone is a safer compound. ( I don't see the warnings on the label for the polish remover.) The balls are 75% cello and 25% camphor. It seems the camphor is the most hazardous part of the mix. I rub Mentholatum on my skin to ease sore muscles and stuffy head. It is 9% camphor?
Anyway you can dissolve the balls and paint the solution on a coil. Let it dry and your coil is plastic coated. Make a paper core and paint it with the mix and when it drys you have a coil form. ( this may take a few coats.)
It's about the journey. Enjoy the trip.

loop update

A quick update on this project. When I installed the plastic tubing for the wire hangers I let it protrude out front and back.

When I blow it up it became a little grainy but you can see the tube. I wrapped one side with a single turn and the other with the ribbon cable. When I get back to the loop I will put a switch so I can select the taps on it. One side will be antenna and ground the other side will be the radio input.
The switch taps will be the terminals for the coil. I may come back and put ribbon on the side with the single loop after I see how it works.

I checked the single turn and it was about 12 uh. If memory serves I didn't write it down.

selector switch knob selection

As I said there are several options. I'm still looking a a couple. I didn't get any shop time today but I did bring in the knob I started yesterday.

I filled the cap with Durham wood putty.

I did two while I was mixing putty.

I plugged one into the board I made yesterday. I may want to paint it? It does look like a good size for my board.

I mounted an armature on it. I think that will be a go. Next shop time I can paint a couple caps and cut some banding for the armatures.
The grooves on the bottle cap make a good grip. I will need to lock the armature with a set screw or some glue. The Durham putty can be drilled and tapped. A little construction cement would work it a fellow didn't want to drill and tap a hole.