Thanks to all of you who replied.
The antenna system is for 160, 80, and 40 meters. 450 ohm OWL (open wire
line) spacing is too close unless many spacers are used, and that would
likely increase losses and increased sensitivity to rain, etc. 800 ohm OWL
has spacing that is not convenient (about 16 to 20 inches depending upon
wire size). So, 600 ohm seems like the most practical OWL considering only
the line itself.
My main concern with using 600 ohm OWL is the insertion loss for the two 50
to 600 ohm baluns. From what I've read, transformers with 3:1 or 4:1 turns
ratio (for 450 ohm or 800 ohm OWL) have negligible magnetic flux flowing in
the core, which doesn't seem to be true for a 50 to 600 ohm transformer.
Therefore, it appears that a 50 to 600 ohm balun would have more loss than
either a 50 ohm to 450 ohm or a 50 ohm to 800 ohm balun of similar
construction. Perhaps the loss, whatever it may be, will be negligible. I
hope to avoid doing a lot of experimenting and just use a proven design with
clear technical parameters (maximum power, insertion loss, and frequency
coverage). Comments, and especially information about proven designs for 50
to 600 ohm baluns would be greatly appreciated.
73, Riki, K7NJ
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