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feed system for 1 feed is VERY sensitive. If you don't build it exactly the way the manual tells you, it won't work. I deviated from the manual only by rotating the 20m feed by a few degrees (45). The result was that 15 meters resonated at 20.2 MHz. 10 and 20 were OK. After playing with the two wire spacers and the hairpin coil for a few hours, I was able to achieve reasonable 15M operation, but then 20M resonated at 14.45 MHz. Due to my inability to do tower work, its stayed that way until this last weekend. I dropped the tower (tilt-over crankup) and re-configured the C31 for 3 coax feeds. The manual says that this involves moving the 15 driven back to an alternative boom position (check!). It also says to remove the 4 inch element tips of the 15 driven (ok, I have a drill, check!). It also says to lengthen the 20 driven by 7.5 inches by using the alternative element tips. (oops.. my C31 didn't come with any alternative tip pieces and the existing tip pieces aren't long enough to telescope out that much). Of course, I hadn't read that detail before dropping the antenna and starting the project. What to do? I drilled out the 20M element tips and re-rivited them to be 3 inches longer which is as much as I could get. Then I reused the 4 inch tips removed from the 15 driven by riveting them to the 20 driven. Kludgy, but effective. Probably not recommended in high wind QTHs. Its back up in the air and works great! SWR in the CW bands of 20, 15, and 10 are all 1.2:1 or less. The 20 driven looks funny with the larger diameter tips, but it works! The advantage of individual feeds are: 1. ease of assembly and tuning Disadvantages are: 1. need a bigger coax switch at the tower Can't recommend a spacing for the EF417, but it will probably affect the C31 15 meter pattern. Farther away is better. 73, Al AD6E In a message dated 10/22/2000 8:47:52 AM Pacific Daylight Time, k4nta@arrl.net writes: << I have a C-31XR and EF-417 on order. My question is what are the advantages or disadvantages of using 1 or 3 coax feeds? I have no plans on using more that one transceiver at a time. In addition, what is the optimum spacing between the C-31XR and the EF-417 17M yagi? >> -------------------------------------------- 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 n4zr@qth.com |
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