Here is how you do it...... Take a T connector and put it on one of the pass loops. Leave the other loop unterminated. Adjust the loop position so that the notch depth is about 9dB for 0.9dB IL through if I remember correctly - this is done like measuring a notch cavity with the spectrum analyzer and tracking generator on the T. Adjust the other loop the same way but ensure that the loops are rotated the same way from the maximum coupling position as observed by the weld mark on the loop (rotated clockwise or counterclockwise). Recheck the first loop's depth and adjust so it is the same. This process makes the in and out loops symmetrically tuned. Measure the pass insertion loss to ensure you have the desired insertion loss. If not, readjust the loop's notch again to a slightly different depth - more for less pass loss and less depth for more insertion loss.
Once both cavities are tuned to frequency, the cable length between them is somewhat critical in length. With the correct length, the individual pass curves add without the need to retune the frequency and the return loss curve will show 2 dips approximately equal and above and below the pass frequency. If you don't get 2.0dB IL with the 2 cans at 0.9dB, then the cable is incorrect. Enjoy!
