FB Pete! It is great to see some new thinking on quad matching. You are
absolutely correct about the impedance issue as the coax center
conductor/shield spacing is fixed. It is my understanding that the dielectric
constant of water is about 5 so you certainly would not want to use 9913 type
cable with its hollow construction that could collect water. Most of my
experience with water and coax is on 144 Mhz where fust a few drops of water
inside a connector (not inside coax) just destroys the phase characteristics
of the line. The effect will be much less on HF of course. You might want to
make up a section for 10 mtrs, terminate it with 100 ohms and squirt water
all over it to see what happens. If it passes that test it probably will be
ok for rain water.
It would be tempting to use ferrites over the outside of coax to create a
balun and use the normal 75 ohm 1/4 wave matching section also.
Please let us know how you configure the system and the results. 73 de K5GW
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