[Elecraft] Opinions please...

[Masleid, Michael A.]

Hello Julius

> Ok, I want to build a balun. It should be able to
> handle 200 Watts RF (safety factor built into this
> number), 80 thru 30 Meters (160M would be nice) and be
> efficient.

Well, I'm guessing here, but I think you'll need to
use ferrite to keep the inductance reasonable.  You
also want to keep the B field low so it doesn't get
hot or non linear.  Let's shoot for 200 gauss peak.

If you were running 200 watts into 50 ohms, you'd need
100 volts on the line, but that would be into a matched
load.  Into a doublet lets say we have a 10:1 VSWR, so
we'll see 1000 volts at the balun.

How many turns?  Lets try 10.  Frequency, 1.8 MHz.

Using Fair-Rite's formula, we'll need 6.26 cm squared
core area.  If you use FT-100-43 I think you'd need
to stack them up until you have a 1" diameter by 5"
long tube.

I might be way off though.

73, de Michael, AB9GV