[TowerTalk] choke / balun design needed

[Jim Brown]

On Mon,4/27/2015 10:02 AM, TexasRF--- via TowerTalk wrote:
> So, is there ANY solution to providing a feedline choke for an OCF dipole
> used with high power?

Assuming coax and reasonably low SWR, it might be possible to "brute 
force" it by using multiple 5K Ohm chokes in series on the line. In the 
early stages of my work on coax chokes, I rigged a special 40M vertical 
dipole in one of my tall redwoods that used the outside of the coax 
shield as the bottom half of the dipole, with a 5K ohm choke a quarter 
wave down the line from the feedpoint acting as the end insulator. This 
places a VERY high voltage across the choke, and it handled 1.5 kW for 
about 15 minutes before the coax melted. :) I replaced the feedline with 
a beefier one and put two of those 5K ohm chokes in series. That DID 
handle 1.5kW for CW and SSB. I didn't test with RTTY. :)

N6BV has shown that if the SWR is high, even the best choke is likely to 
fry due to differential loss. That's in addition to the common mode 
dissipation.

73, Jim K9YC