To: File turnstile_tuning.wpd

From: Jon Hagen

Date: 12-15-03

Subject: Turnstile Tuning

Summary: The turnstile can be tuned in place as follows:

1. Make sure the side arm positions differ by 1/4 of the guide wavelength. The absolute positions control the polarization of the wave, but don't matter when adjusting the tuning posts.

2. Adjust the tuning posts to acheive simulataneously the best input match at the transmitter port and the least coupling to the receiver port. Note: the coupling to receiver port can be measured through the usual receiver connection; it is not necessary that the receiver port see a matched load, since, when

tuned up, there will be no coupling to this port. The connection to the transmitter port is important:

Take the 3-short WR430 Waveguide cal kit to the carriage house and use it to calibrate a reference plane at the flange of whatever coax-to-waveguide adapter is being used.

Week of Dec. 8, 2003