using toroidal inductors in tube transmitters

[KC2ZFA]

This is a pretty hand calculator:

http://www.dl5swb.de/html/mini_ring_core_calculator.htm

it really is...thanks.

Am I right to think that for higher power you stack cores ? or is it better to use the higher # cores (300 or 400) ?

[KK4RF]

Gentlemen:
     Got the rig finished enough to try on 160 tonight. Made a qso with Bob, W8PC, somewhere in South Carolina. He said my rig sounded good there.
     Needs a lot of work to get it all together and enclosed. I hope I get it all done someday. But it was a fun project and if anybody wants to build a simple two-tube cw rig, I highly recommend this easy to build transmitter from 1969 QST, by Lew McCoy.
     Many thanks to all who helped me in this project.   ---Marty, KK4RF---

[Steve - K4HX]

Congratulations. Hope to catch you on the air with the new rig soon.

[KM1H]

Marty, all the 1500W+ amps Im aware of use 27 or similar thick tape on the core and Teflon insulated wire or sleeving.

At least one commercial amp used them to 40 but at that power level you need one core per band. Command Tech tried 160/80 with one core and customers were burning them up.

And I converted many SB-220's to add 160 using a pair of T225-2's back when 1500W became legal, tape and Teflon of course. Sold kits also.

[KK4RF]

Thanks, Steve. Hope to catch you on 160.
Carl, thanks for the info on the linear amps and the protective tape. No argument that this is a best practice guideline, i.e. using the protective tape on the cores. I found numerous other examples on the internet.  i plan to get some of the Scotch #27 soon and rewind the  amp pi-network inductor. Curiously, for now, I've not noticed any heating whatever on the core itself. Thanks again, Carl.
     73s, Marty, KK4RF

[KM1H]

If that core was heating you wouldnt have any output

[KK4RF]

Carl,
     Good point. 73s,  Marty