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## Re: [TowerTalk] Measuring Coax Loss

 To: , "'Tower and HF antenna construction topics.'" Re: [TowerTalk] Measuring Coax Loss "Gary Schafer" garyschafer@comcast.net, "Tower and HF antenna construction topics." Thu, 11 Feb 2010 21:11:54 -0500 mailto:towertalk@contesting.com>
 Hi Rick, I don't think that I have used the method that you describe. What happens when the cable length approaches a quarter wave length? Or is this only valid at a small fraction of a wave length? 73 Gary K4FMX > > If I wanted to accurately measure the loss on a 10 ft piece of cable, > I would short circuit one end. I would put a TEE on my signal > generator front panel connector and connect a power meter sensor > to the side port of the TEE. Next, I would note the power meter > reading of the sig gen output. Then, I would then drive the unshorted > end > of the 10 ft cable with the third port of the TEE. The cable loss can > be > very accurately calculated by the difference between the power meter > reading with vs without the coax under test attached. The lower the > power > meter reading, the lower the loss of the cable. For example, if the > loss > of the 10 ft cable is 1% (about 0.043 dB), the power meter will read > 28 dB lower when loaded by the coax than unloaded. > > You don't need any heroically accurate instruments to make this > measurement. You could almost do it using the S-meter on a radio if you > previously checked the S-meter characteristics. A 3 dB error in the dB > measurement only represents a 10% error in the cable loss, due > to the way the math works. You can also use a variable attenuator > on the sig gen to make the measurement. In that case, the > S-meter is only used at one setting and its calibration is irrelevant > (this is a well known technique). > > Rick N6RK > > _______________________________________________ > > > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk
 Current Thread Re: [TowerTalk] Measuring Coax Loss, (continued) Re: [TowerTalk] Measuring Coax Loss, Mike Besemer \(WM4B\) Re: [TowerTalk] Measuring Coax Loss, Jim Brown Re: [TowerTalk] Measuring Coax Loss, Mike Besemer \(WM4B\) Re: [TowerTalk] Measuring Coax Loss, Stan Stockton Re: [TowerTalk] Measuring Coax Loss, Mike Besemer \(WM4B\) Re: [TowerTalk] Measuring Coax Loss, Dan Schaaf Re: [TowerTalk] Measuring Coax Loss, Mike Besemer \(WM4B\) Re: [TowerTalk] Measuring Coax Loss, Mike Re: [TowerTalk] Measuring Coax Loss, jimlux Re: [TowerTalk] Measuring Coax Loss, Rick Karlquist Re: [TowerTalk] Measuring Coax Loss, Gary Schafer <= Re: [TowerTalk] Measuring Coax Loss, Richard (Rick) Karlquist Re: [TowerTalk] Measuring Coax Loss, Richard (Rick) Karlquist Re: [TowerTalk] Measuring Coax Loss, jimlux Re: [TowerTalk] Measuring Coax Loss, jimlux Re: [TowerTalk] Measuring Coax Loss, Cqtestk4xs Re: [TowerTalk] Measuring Coax Loss, Mike Besemer \(WM4B\) Re: [TowerTalk] Measuring Coax Loss, Dan Schaaf Re: [TowerTalk] Measuring Coax Loss, Mike Besemer \(WM4B\) Re: [TowerTalk] Measuring Coax Loss, Roger (K8RI) Re: [TowerTalk] Measuring Coax Loss, Cqtestk4xs