In a message dated 4/27/2015 12:59:27 P.M. Central Daylight Time,
jim@audiosystemsgroup.com writes:
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
Thanks for the information Jim. It all makes good sense down to the part
about differential loss. That is a new term for me so I did a Google search
for "coaxial cable differential loss" to see what it means.
Guess what: there was nothing shown for that subject. Wonder just what it
is about?
Gerald K5GW
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