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As there appears to be somewhat of an "urban legend" growing concerning the tuning of the C31XR, I thought a few comments might be helpful, even though you may find it repetitious. The C31XR uses a combination open and closed feed system to excite the three bands by a single feedline. The feedline arrives at the 10 meter driver and through a closed sleeve comprised of two wires, the energy makes it way to the 20 meter driver. The 20 driver and the 15 meter driver form an open sleeve to facilitate 15 meter excitation. Some installations have trouble getting the 15 meter resonance within the band. We have found that this is easily corrected by bringing the two wires of the closed sleeve in close proximity which then raises the 15 meter resonance to within the band. This method will preserve the lengths and geometries of the sleeves and therefore is strongly recommended over any element length changes. The manuals of recent vintage have the following: _____3) The next part installs the parallel driver wires between the 10 mtr driver feedpoints and the 20 mtr feedpoints. _____a) Locate the two, long wires with lugs on each end. _____b) Slip the lug from one end of each of these two wires to the 10 mtr driver feedpoint screws. _____c) Add a #10 flat washer, split lockwasher and a nut - leave loose at this time. _____d) Place a flat washer on each of the 20 mtr feedpoint screws and slip the other end of each wire over the 20 mtr screws. _____d1) Please be sure the wires are parallel (not crossed). _____d2) It is recommended these two wires be taped together with widths of vinyl tape spaced every three inches. Do not cross these wires. _____e) Add the 20 mtr hairpin coil across the 20 mtr feedpoint screws. _____f) Slip on a #10 flat washer, split lockwasher and nut. _____g) Align the wires and matching coil, then tighten the nuts on BOTH the 10 AND 20 mtr drivers. _____h) Adjust the turns on the 20 mtr hairpin coil for a small space between turns (1/8"). Any antenna installation is unique. Many factors affect all our antennas including ground topography and conductivity, structure, and of course other antennas. the presence of these objects are responsible for variations in the "tuning" of the C31XR. I've written about this subject previously on the Tower Talk reflector, so you can search the archives for more information if you like. As always, if you have questions or comments, please just write. The E-mail volume has been overloading me, so my response may be delayed, but it will come! Thanks, Natan W6XR Force 12 East Ithaca, NY FN12sk force12@qth.com -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force 12 Web site: http://www.qth.com/force12 Submissions: send to Force12Talk@qth.com To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk For problems with the list, contact force12@qth.com |
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