I've been experimenting with ways of constructing 75 Ohm twin feeder for
a Hexbeam application - it's now very difficult to get the heavier duty
commercial cable - the only manufacturer in UK has ceased production.
On my website I recommend using 50 Ohm coax for the Hexbeam band
interconnects, but folk who opt to use the higher power handling RG213
sometimes have difficulty making off the ends. Twin feeder would be
easier to use, and as long as its characteristic impedance was less
than about 80 Ohms it would work fine.
It turns out that 2 lengths of RG58 taped side by side produce the right
value Zo, using the braids as "fat" conductors spaced by the PVC
jacket. In a final version I would probably hold them together using
heatshrink tubing. I only need short lengths - maximum 24" - so losses
are not likely to be an issue.
I wondered what's a good way of estimating the power handling capability
of this arrangement. What's likely to be the limiting factor - the
voltage breakdown through the PVC ?
Grateful for any views.
Steve, G3TXQ
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