No, using a T connector on the loop, you have a notch cavity although it is a non symmetrical notch - doesn't matter. You adjust the loop for a notch depth of say 9dB using the T one loop at a time and that balances the impedances of the loops in and out so that they are the same. The notch depths will vary on the frequency of the cavity for a given insertion loss. This is how the cavities are set up at Sinclair. They know what depth of notch to set the loop at to give a particular pass response. Quick, repeatable and reliable.
--- In Repeater-Builder@yahoogroups.com, Larry Horlick <llhorl...@...> wrote: > > So you actually come up with an RL value and equate to an IL value? > > lh > > On Wed, Apr 21, 2010 at 9:08 AM, hfarrenkopf <hfarrenk...@...> wrote: > > > > > > > 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! > > > > > > >
