K9STH

05-25-2011, 09:31 PM

While winding the r.f. choke for my latest amplifier project I "discovered" a very handy thing, 26 gauge enameled wire close winds at as close to 50 turns per inch that you could hope for! I did have a ceramic form 1 inch in diameter which I used. However, it would certainly be possible to use 1 inch PVC (or a different diameter) on which to wind the r.f. choke.

You can calculate the effective inductance of a single winding choke at the following URL:

http://www.daycounter.com/Calculators/Air-Core-Inductor-Calculator.phtml

Copying a couple of designs on the Internet for an amplifier covering 160-meters through 10-meters the designs showed a 195 mH r.f. choke in the B+ line to the final amplifier tubes. Other designs, using various tubes, show different values. Although I was trying for 195 mH I did go ahead and calculate the inductance for every quarter-inch from 1 inch long coil to 4 inches long. Those figures are in a table which accompanies this post.

I used the mentioned calculator when I was designing the final tank coil for my 160-meter amplifier using a pair of GI-7bT tubes. That coil worked very well.

Also attached is a photo of the r.f. choke that I am going to use in my new amplifier.

Since winding r.f. chokes applies to all sorts of home brew equipment I am starting this thread in the home brew forum instead of the amplifier forum. Also, the cited inductance calculator is not just for r.f. chokes. It can be used to calculate the diameter, number of turns, length, etc., of coils used in transmitters, receivers, converters, traps, etc.

Glen, K9STH

65357 65358

You can calculate the effective inductance of a single winding choke at the following URL:

http://www.daycounter.com/Calculators/Air-Core-Inductor-Calculator.phtml

Copying a couple of designs on the Internet for an amplifier covering 160-meters through 10-meters the designs showed a 195 mH r.f. choke in the B+ line to the final amplifier tubes. Other designs, using various tubes, show different values. Although I was trying for 195 mH I did go ahead and calculate the inductance for every quarter-inch from 1 inch long coil to 4 inches long. Those figures are in a table which accompanies this post.

I used the mentioned calculator when I was designing the final tank coil for my 160-meter amplifier using a pair of GI-7bT tubes. That coil worked very well.

Also attached is a photo of the r.f. choke that I am going to use in my new amplifier.

Since winding r.f. chokes applies to all sorts of home brew equipment I am starting this thread in the home brew forum instead of the amplifier forum. Also, the cited inductance calculator is not just for r.f. chokes. It can be used to calculate the diameter, number of turns, length, etc., of coils used in transmitters, receivers, converters, traps, etc.

Glen, K9STH

65357 65358