Note: This diagram does not show a second relay used to create a broadside pattern (simply shorts across the A and B terminals, so each antenna is fed by the same length of feedline). If you want to keep each antenna’s radial system isolated from the other antenna, use a DPDT relay instead — which will let you switch both the shield and the center conductors of each feedline.

Christman Phasing Calculator Operating frequency: Mhz Coax velocity factor: Vf Measuring your 71-degree phasing line The 71-degree phasing line should be: 0.00 ft or 0.00 m. The 71-degree phasing line is 90 degrees at 0.00 Mhz. Cut the coax to the suggested length plus a few inches, in case your velocity factor is not quite right. Leaving one end of the coax open, set your RF analyzer to 0.00 Mhz and trim the coax until you see minimum Z impedance. You now have a length of 71 degrees at your desired operating frequency. Measuring your 84-degree feedlines Each 84-degree feedline should be: 0.00 ft or 0.00 m. The 84-degree feedlines are 90 degrees long at 0.00 Mhz. Cut the coax to the suggested length plus a few inches, in case your velocity factor is not quite right. Leaving one end of the coax open, set your RF analyzer to 0.00 Mhz and trim the coax until you see minimum Z impedance. You now have a length of 84 degrees at your desired operating frequency.

Here’s how to cut them to the correct length:

Connect the antenna analyzer to one end of a cable,other end left open.
Hold the coax centre and shield against the analyzer’s connector,
so there is no extra length presented by a PL259 —
Even a 1/4-inch of extra length makes a difference.

Trim the coax until the analyzer indicates minimum Z impedance —
this is where the line is precisely 1/4 wavelength (90 degrees) long, as follows:

• For 7.050 mhz, the 84-degree feedline is 90 deg. at 7.554 mhz.
• For 7.050 mhz, the 71-degree phasing line is 90 deg. at 8.937 mhz.