Date: Mon, 20 Dec 93 04:30:10 PST From: Info-Hams Mailing List and Newsgroup Errors-To: Info-Hams-Errors@UCSD.Edu Reply-To: Info-Hams@UCSD.Edu Precedence: Bulk Subject: Info-Hams Digest V93 #1485 To: Info-Hams Info-Hams Digest Mon, 20 Dec 93 Volume 93 : Issue 1485 Today's Topics: SWR tweeking: Details, details... Send Replies or notes for publication to: Send subscription requests to: Problems you can't solve otherwise to brian@ucsd.edu. Archives of past issues of the Info-Hams Digest are available (by FTP only) from UCSD.Edu in directory "mailarchives/info-hams". We trust that readers are intelligent enough to realize that all text herein consists of personal comments and does not represent the official policies or positions of any party. Your mileage may vary. So there. ---------------------------------------------------------------------- Date: Sat, 18 Dec 1993 18:50:23 GMT From: mvb.saic.com!unogate!news.service.uci.edu!usc!howland.reston.ans.net!cs.utexas.edu!swrinde!emory!rsiatl!ke4zv!gary@network.ucsd.edu Subject: SWR tweeking: Details, details... To: info-hams@ucsd.edu In article alanb@sr.hp.com (Alan Bloom) writes: >Gary Coffman (gary@ke4zv.atl.ga.us) wrote: > >: Well that depends on why you're doing the SWR measurement, and how well >: you know the characteristics of your line. If you know your particular >: line characteristics, you can make the measurement *anywhere* that's >: convienent and use the Smith Chart, or the formulas in the Antenna Book >: to determine what complex impedance appears at any point in the system. > >An SWR meter does not measure complex impedance, no matter where it is >placed. It measures the magnitude (but not the phase) of the reflection >coeffficient and displays that on a meter calibrated in units of SWR. Absolutely correct, and what I said in my second paragraph when talking about measurements at the antenna. All you get is a number that can be translated into the absolute value of the complex impedance mismatch, not whether it's resistive or reactive, or the sign if reactive. There are ways of determining those things with the aid of a SWR meter, but it requires you to vary another independant variable, frequency. >Assuming a lossless feedline, the SWR is the same at all points along >the line. No real line is lossless, though some lines are much better than others. Lossless lines aren't required, but knowledge of your line's characteristics is required. Gary -- Gary Coffman KE4ZV | I kill you, | gatech!wa4mei!ke4zv!gary Destructive Testing Systems | You kill me, | uunet!rsiatl!ke4zv!gary 534 Shannon Way | We're the Manson Family | emory!kd4nc!ke4zv!gary Lawrenceville, GA 30244 | -sorry Barney | ------------------------------ End of Info-Hams Digest V93 #1485 ****************************** ******************************