I Checked a bunch of really old e-mail, and notes. The folk's who
duplicated the KK5DR plate choke, using 1/2" type 43 rod, stuffed into the
inside of a hollowed out 1" OD Teflon rod
had nothing but grief. All the rods overheated ! In some cases, the rod
actually launched itself out the top !
Either 1" type 43 rod is required, [like several type 43, 1" Od beads
slid over the 1/2" rod].... or several type 43 rods bundled together.
Perhaps type 43 material is the wrong stuff to be using for a plate
choke...esp considering the typ plate load Z's involved ??
Type 43.... 1" OD bead's, slid over 393 Teflon coax makes for excellent
Choke baluns. The 1/2" x 8" long type 43 rods work great for
Bifilar's. But in both those cases,
the Z is only 25-50 ohms.
What would be an excellent solution, would be a higher current version of the
RF parts /Ameritron plate choke. I have asked a few times what ga wire is
used in the Ameritron choke,
and can't get a straight answer. I believe it's around 28 ga. A version
made with 22 ga wire would be the ultimate solution. I know how Tom
designed the Ameritron choke.
However, I'm not prepared to sit there in the shop for months, with a vna,
etc, trying to park resonances. The 2 x choke + relay version was a
cheap way to get around the problem.
Incidentally, the choke relay coil was activated by a 3rd wafer on the tuned
input switch.
Later.... Jim VE7RF
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