Brian, VA3HJ's answer is correct but incomplete. The 75 ohm cables must each be 1/4 wavelength long. The actual value needed for the phasing cable characteristic impedance is 70.7 ohms. Essentially, taking a 1/4 wavelength of  70.7 ohm cable will transform 50 ohms resistive to 100 ohms resistive. Then take the two 100 ohm impedances and parallel them to get back to 50 ohms where you can use any length of 50 ohm cable to get to the transmitter. 

Fred
K9SO

"The characteristic impedance of cables must be such that the proper length of cable will provide an impedance transformation from 50 ohms at the antenna end to 100 ohms at the connecting point. A quarter wavelength of cable that provides the proper characteristic impedance can transform the 50-ohm impedance of each antenna to 100 ohms at the connection point. 

The characteristic impedance of cables L1 and L2 must be 70.7 ohms. Because 75-ohm cable is readily available, it is generally used to make the phasing harness. Standard 50-ohm impedance cable is used for cable L3, which extends from the connection point to the transceiver."


On Monday, November 29, 2021, 05:42:55 AM EST, V Chu <ve3xre@gmail.com> wrote:


Brian 

You can use 2 75ohm cable to connect each antenna and join them with a coaxial splitter then 50ohm cable to your Transmitter. 

de VA3HJ mobile

On Sun., Nov. 28, 2021, 23:23 Brian Clark <decompudoc@gmail.com> wrote:
Hello Everyone,

I have two Dual-Band 2 Meter/440 Yagi's  that I would like to use on a Rotator, with one in the vertical polarity and one in horizontal.

Is there a phasing circuit or system that someone can recomend to allow both of these antennas to coexist on one coax input to my radio?

Thanks,

Brian
KF6FES

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