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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>People of a certain age might remember Rabbit ears. Folks would do all kinds of weird things to get the station we wanted. Lengthening, shortening, adding bits of aluminum foil. Almost nobody understood antenna resonance but they had some idea of changing the antenna made it better or worse. The other humorous factor is that stepping away from the antenna, might make it worse again. Often friends and relatives were forced to stand next to the antenna, unable to see the screen so the rest of us could see whatever.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Impedance depends on frequency. That depends on what else is nearby the antenna. The director and reflector, as is everything around, part of the SWR. Measuring the driven element alone or measuring it with the reflector, then adding the director is a waste of time in a Yagi. Put the antenna together as designed for the band you want, then measure. Also make your measurements with the antenna at the height and in the environment you anticipate. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>It would be interesting to know if the 2.5:1 is true for all 6m frequencies. The impedance will not be the same at all frequencies either. That’s also not a horrible SWR, not great but not horrible. A tuner can compensate for the rest. Isn’t there a function in the nano to chart impedance / SWR across an entire band? If someone has a rig-expert that can do it for sure.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>-73-<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>W1GCF<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Geoff<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> bars [mailto:bars-bounces@w1hh.org] <b>On Behalf Of </b>Tim KC1RET<br><b>Sent:</b> Saturday, September 10, 2022 9:54 AM<br><b>To:</b> bars@w1hh.org<br><b>Subject:</b> [bars] Impedance of yagi<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><div><div><p class=MsoNormal>So I'm trying to throw together a 3el 6m yagi for the VHF contest this weekend. I built one based on a design for a wire + PVC beam I found on da Google (<a href="http://ehpes.com/n6mw/WireYagi2.pdf">http://ehpes.com/n6mw/WireYagi2.pdf</a>). Mine has a bit less duck tape. ;-)<br><br><br><o:p></o:p></p></div></div><div><div><p class=MsoNormal>I tested only the driven element with my nanoVNA, spot on 1.1 at my target of 50.2 (FT8). I added the reflector - still 1.1. (All measurements taken at about 10ft. elevation). I added the director - the lowest SWR is now 2.5:1 at the same freq. (the SWR low point did not change).<br><br><br><o:p></o:p></p></div></div><div><div><p class=MsoNormal>The measured impedance dropped from 50.2 to around 30 after adding the director. I took the wire off the director element support (aka PVC pipe) and the SWR went back to 1.1:1. I did check that the elements were parallel (as best as can be accomplished with PVC tubing and bits of cutting board).<br><br><br><o:p></o:p></p></div></div><div><div><p class=MsoNormal>What variables in the director (length, spacing from DE, etc.) would cause this?<br><br>73<br><br>Tim - KC1RET<br><br><o:p></o:p></p></div></div></div><div><p class=MsoNormal>-- <br><br><o:p></o:p></p><p><span style='font-size:7.5pt;font-family:"Verdana","sans-serif"'>Courageously sent from a non-Apple device that <em><span style='font-family:"Verdana","sans-serif"'>includes</span></em> a headphone jack.<o:p></o:p></span></p><div class=MsoNormal align=center style='text-align:center'><hr size=2 width="100%" align=center></div><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0><tr><td style='padding:0in 0in 0in 0in'><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0><tr><td width=150 style='width:112.5pt;padding:0in 0in 0in 0in'><p class=MsoNormal><a href="https://kc1ret.com/img/kc1ret-qsl-card-front-v3.png"><span style='text-decoration:none'><img border=0 width=130 id="_x0000_i1026" src="https://kc1ret.com/img/kc1ret-qsl-card-front-v2-sm.png"></span></a><o:p></o:p></p></td><td style='padding:0in 0in 0in 0in'><h3>Tim Carter - KC1RET<o:p></o:p></h3></td><td width=30 style='width:22.5pt;padding:0in 0in 0in 0in'><p class=MsoNormal> <o:p></o:p></p></td><td width=30 style='width:22.5pt;padding:0in 0in 0in 0in'><p class=MsoNormal> <o:p></o:p></p></td><td style='padding:0in 0in 0in 0in'><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0><tr><td width=30 style='width:22.5pt;padding:0in 0in 0in 0in'><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0><tr><td style='padding:0in 0in 0in 0in'><p class=MsoNormal><img border=0 width=13 id="_x0000_i1027" src="https://receptiveaudio.com/static/phone-icon.png"><o:p></o:p></p></td></tr></table></td><td style='padding:0in 0in 0in 0in'><p class=MsoNormal><a href="tel:1.978.710.0133">+1.978.710.0133</a><o:p></o:p></p></td></tr><tr><td width=30 style='width:22.5pt;padding:0in 0in 0in 0in'><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0><tr><td style='padding:0in 0in 0in 0in'><p class=MsoNormal><img border=0 width=13 id="_x0000_i1028" src="https://receptiveaudio.com/static/email-icon.png"><o:p></o:p></p></td></tr></table></td><td style='padding:0in 0in 0in 0in'><p class=MsoNormal><a href="mailto:kc1ret.radio@gmail.com">kc1ret.radio@gmail.com</a><o:p></o:p></p></td></tr><tr><td width=30 style='width:22.5pt;padding:0in 0in 0in 0in'><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0><tr><td style='padding:0in 0in 0in 0in'><p class=MsoNormal><img border=0 id="_x0000_i1029" src="https://receptiveaudio.com/static/link-icon.png"><="" td="" width="13"> <o:p></o:p></p></td></tr></table></td><td style='padding:0in 0in 0in 0in'><p class=MsoNormal><a href="https://kc1ret.com">https://kc1ret.com</a><o:p></o:p></p></td></tr></table></td></tr></table><p>"Computers are incredibly fast, accurate and stupid; humans are incredibly slow, inaccurate and brilliant; together they are powerful beyond imagination." -- <i>Albert Einstein</i><o:p></o:p></p><p style='-webkit-margin-after:.5em;-webkit-margin-before:.5em'><span style='font-size:7.5pt;font-family:"Verdana","sans-serif"'>Warning: Spelling errors in this message are the product of a poor school system. Pay teachures more than athletes.<br>IMPORTANT: This email is intended for the use of the individual addressee(s) named above and may contain information that is confidential privileged or unsuitable for overly sensitive persons with low self-esteem, no sense of humor or irrational religious beliefs. If you are not the intended recipient, any dissemination, distribution or copying of this email is not authorized (either explicitly or implicitly) and constitutes an irritating social fauxpas. No animals were harmed in the transmission of this email, although the mutt next door is living on borrowed time, let me tell you.<o:p></o:p></span></p></td></tr></table><p class=MsoNormal><o:p> </o:p></p></div></div></body></html>