jawod wrote:
But...the twin lead is connected directly to coax with no balun. Isn't
this a mismatch?

The ladder-line is NOT used as RF transmission line.
It is used for DC current and for RF antenna current.
This is just an ordinary coax-fed dipole with an extra
wire to carry the DC. There is no BALanced to UNbalanced
RF junction to worry about.
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73, Cecil http://www.w5dxp.com