[Antennas] Some thoughts on baluns

[Sandy and Kees Talen]

Thanks for the response. You are right in that a consideration is 
overheating the beads and changing characteristics. What I was 
trying to do was use a choke balun in a <200w 160m to 10m tuner. 
So far I'm at two large type #77 beads with 4 turns, 4.5" dia, of 
RG/58U through them. The reasoning is that the 4 turn coil fixes 
some shortcomings at 21-30Mhz, the two type #77 work well at 
160m, running multiple turns through them increases their 
effectiveness approx 16 times (and increases heat ?  ...I thought 
more choke impedance decreases the heat) ....the down side is 
any heat generated  ...which I hope to offset some by the fact 
that the 4 turn coil will take some of the heat due to it's impedance. 
Maybe add a few (2-3) more ferrites to distribute whatever heat. 
I've made impedance measurements and it looks good from 160m 
to 10m. I have NOT done any power testing ....and may have to 
get some hot dogs and fixins ready. 

I did try more mass with a larger, #43 material, flat ribbon cable 
ferrite spaced further apart with additional ferrite material but 
the results were poor at 160m. I was going to try two of these 
but haven't had a chance.

I don't want to use a piece of coax with 50+ beads (W2DU), plus 
all indications are that they could be improved at 10m. Is that 
where they get hot ...10m and 15m ? (low impedance) or is it 
80m ? (high impedance) ....maybe add a 6 turn 4" coil to fix the 
10m low impedance ?

The backup plan is the use a large 30ft long piece of coax (like 
in the AG6K tuner) with a "T" BNC connector at 6 turns and 
figure out how to switch that so the 20m-10m performance is 
satisfactory. 

Great fun.

73  Kees K5BCQ