I was thinking about the seams of the extrusion being oxidized and not making a good connection but I never heard of the results of such as you describe but then the resloks were cut to the design lengths. I suppose that if it were a poor connection, the high voltage near the end of the resonator may be absorbed and may cause the unloaded Q of the cavity to be reduced but that should only effect the insertion loss and not the notch depth but that could be another weird effect.
Cutting the Reslok extrusions square and equal is very difficult unless you have the right tools. The loop size should be smaller than the VHF loop but I don't have those details. I think Dave may have had a picture of his modified loops. The size is not that important in the Q loop as long as you can get the insertion loss setting and notch depth required for the frequency spacing. Harold --- In [email protected], "holycow619593" <[EMAIL PROTECTED]> wrote: > > Yes, I especially made a point to replace and torque down all the 60 > some odd screws for the top and bottom plates into the body. I pity > those who worked before the advent of high speed power screw guns. > I even replaced some of the screws to ensure a tight fit. > > I also took the time to clean the contact points between the top of > the cavities, the connector bodies' contact surfaces with the top > plate, the plate, and dry polish the tuning rods and contacts. I > often come across issues up here (pacific northwest) where the ambient > moisture caused corrosion to occur between all these points making > tuning almost impossible. > > The only other thing I can think of that was different before and > after trimming the cavities was I cleaned the contact area between the > extrusions when I disassembled the cavities to cut them down. > > I found the tuning capacitors were no longer near their bottom of > travel once the cavities were trimmed. I was able to back off the > caps at least a full turn and a half. > > Any idea what the loop measurements and geometry is for the 2221? > > > --- In [email protected], "Harold Farrenkopf" > <hfarrenkopf@> wrote: > > > > The extra length of the VHF cavity used for the 220MHz duplexer should > > do nothing to the tuning, insertion loss or notch depths. I suspect > > there may be another issue with your observed results. > > > > Did you measure the poor performance without tightening or inserting > > ALL the screws on the top plate? > > > > I know for a fact that the length will not effect the performance of > > the cavity once the length of the resonator bottom is beyond the > > capacitive tuning effects. There is no effect of the bottom cover/cap > > except for dust protection. > > > > Harold (ex Sinclair systems engineer) > > > > --- In [email protected], "holycow619593" > > <holycow619593@> wrote: > > > > > > I've noticed that without reducing the size of the cavities, the depth > > > of the notches would only reach 60dB. When I reduced the length of > > > the cavities with a block inserted up the bottom of the cavity, the > > > notch achieved 80dB and the insertion loss dropped from around 3dB to > > > less than 1.2dB. > > > > > > I've read on a number of posts others have found the length of the > > > cavities didn't matter. As a test, after tuning the modified > > > duplexer, I tested the unit on a service monitor with a 50W > repeater. > > > > > > The receiver desense on TX was well in excess of 6dB, indicating a > > > lack of isolation after tweaking the trimmer capacitors. Upon > > > reducing the cavity length and slightly retuning the notch points with > > > the capacitors, the duplexer now exhibited 85+dB of isolation, and no > > > appreciable desense on transmit. As a seasoned commercial tech with > > > many years working on Sinclair products, I found that until I reduced > > > the cavity length, the duplexer would not achieve spec. > > > > > > Does anyone have the length of the coupling loops for the Q2221E? > > > > > >
