Tuesday, May 29, 2018

crystal radio step 5

So we could use a 182uh coil. How to make one is the question. Looking back at professor coil we see wire options.  If you set the pins at 5" and wind an over - under wrap the medium would be 5" so I use that for example to see how the turn count works out.

Looking at the chart you see it list a range of wire sizes and calculates the table each time you change the turn count. The table is in standard wire size and you want to use litz so how does that work? Time to look at the supplier's catalog.

Litz catalogue

Go to page 129 for the wire specs. Skipping over the math just look at the wire sizes and construction.

For medium wave you need #46 or #48 wire to see the benefit of litz over magnetic wire or stranded wire. Mike used 660/46. His wire was 660 strands of #46 wire. Now look at more of the data.

To use the data from the calculator you need to know the wire gauge or OD so you can look it up on a wire chart.

Mike used 660/46. The yellow high light 3rd and 4th column. So 660/46 is 1st column - #18 wire gauge equivalent.

So tabulating the results from above:
10T - 23.6 uh
20T - 81.8 uh
30T - 162.6 uh
40T - 258.9 uh
He said he used 182 uh @ 36 turns but he inter-wound a smaller wire which would effect the inductance. The calculator assumes the coil is close wound. In order to get an accurate result it needs the width of the basket (length of coil).
The program uses turns per inch and turns to calculate the coil length. With the interweave we have some room for error. The value given is a measured value the calculator says 218.9 uh. Stretching the coil to insert 18 turns of second coil will reduce the value.

That's about all I know. You should be able to use what you have available and make the coils using the program.
Good luck.

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