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Thanks to a tip from a user, we have identified a potential source of abnormal VSWR on 10 meters. I have had several installations that had high VSWR on 10 meters, particularly on the high part of the band. The problem was not model dependent, nor did it seem to be environment dependent and the VSWR often changed independent of power used. This last week I was working with a customer who is using a (C3E) that had high VSWR on 10 meters. The customer reported he eliminated the problem by removing a low-pass filter in the line. Once the LP filter was gone, the VSWR behaved per specification. We (Tom and I) thought about this and swept a convenient LP commercial filter and was not surprised to find the filter introducing an impedance anomaly AND a significant amount of attenuation well into the 10 meter band! Five out of five installations experiencing this high 10 meter VSWR problem fixed the problem by removing the LP filter! All of the problem filters were of the same manufacturer. So, if you don't think things are quite right on 10 meters, look at your use of a LP filter as a very possible problem initiator. 73 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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