I built the ocfd and balun from Mikes class and have been using it ever since. I run up to 500 w so I had to stack two cores to avoid overheating (thanks to Wally WA1LY for selling me his unused core from the class project). Back when Mike was still with us we used to have a sked whenever he went to Michigan and I seemed to strap everyone else out even without the amp so the antenna works. I used to have it as inverted vee with center at 60 feet. That branch broke so now it is only 45 or 50 feet at high point but still works great on 40 and 80. Works on 20 and 10 too but I have the hex beam for that (which N1IW helped put up along with N1HTS, WO1N, and K0TV(sk)).<br>Art<br>NF1A<br><br><br><br><br><br><br>Sent from Xfinity Connect App<br><br><br><br>------ Original Message ------<br><br>From: apizer@comcast.net<br>To: W1hh, Paul Pellegrini<br>Sent: December 6, 2020 at 11:11 AM<br>Subject: Re: [bars] Construction of an 80M OCF antenna<br><br>Google n1iw ocfd presentation<br>He taught a class on this and also Balun construction at bars we built them as a class project<br>Sadly mike is now sk and and left us way to soon<br>RIP om mike<br><br>Art<br>Nf1a<br><br><br><br>Sent from Xfinity Connect App<br><br><br><br>------ Original Message ------<br><br>From: Paul Pellegrini via bars<br>To: W1hh<br>Sent: December 6, 2020 at 10:33 AM<br>Subject: [bars] Construction of an 80M OCF antenna<br><br><html><head></head><body><div class="yahoo-style-wrap" style="font-family:times new roman, new york, times, serif;font-size:16px;"><div dir="ltr" data-setdir="false"><div><p class="ydp55647da7MsoNormal">I like OCF dipoles because they offer the ability to be
multiband installations which can be fed with a single piece of 50-ohm
coax.<span> </span>I have a one-acre suburban lot, so
I have room for an 80M OCF dipole.<span> </span>The
half wavelength for 80M is about 126 feet, so you need a straight run of that
length.<span> </span>The objective of this
installation was to have as many resonant ham bands as possible with a single
antenna and a single coax feed line.<span> </span>The
OCF is usually cut in a length ratio of 2 to 1.<span>
</span>For 80 meters those lengths are 84 feet and 42 feet.<span> </span>Here are some of the experimental results for
installation of my OCF.</p>
<p class="ydp55647da7MsoListParagraphCxSpFirst"><!--[if !supportLists]--><span style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:Symbol"><span>·<span style="font-style: normal; font-weight: normal; font-stretch: normal; font-size: 7pt; line-height: normal; font-family: "Times New Roman";">
</span></span></span><!--[endif]-->Make the dipole for the low end of the 80M band.<span> </span>Cut for 3.6 MHz one gets resonances for 7.2Mhz,
14.4MHz and 28.8MHz.<span> </span>It also works on
18.1MHz.<span> </span>These bands can be worked
without an antenna tuner.<span> </span>Most other
bands can be used with an antenna tuner.</p>
<p class="ydp55647da7MsoListParagraphCxSpMiddle"><!--[if !supportLists]--><span style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:Symbol"><span>·<span style="font-style: normal; font-weight: normal; font-stretch: normal; font-size: 7pt; line-height: normal; font-family: "Times New Roman";">
</span></span></span><!--[endif]-->4:1 baluns are commercially available and are
suitable for a 200 ohm feed point.<span> </span>The
impedance of an OCF is about 150 ohms which indicates a 3:1 balun which is not
generally available.</p>
<p class="ydp55647da7MsoListParagraphCxSpMiddle"><!--[if !supportLists]--><span style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:Symbol"><span>·<span style="font-style: normal; font-weight: normal; font-stretch: normal; font-size: 7pt; line-height: normal; font-family: "Times New Roman";">
</span></span></span><!--[endif]-->Using a 4:1 balun means you must find the 200
ohm feed point on the 126 foot wire.<span>
</span>Finding the correct lengths for the shorter and longer sections involves
experimentation.<span> </span>My final lengths were
40 feet and 88 feet.</p>
<p class="ydp55647da7MsoListParagraphCxSpLast"><!--[if !supportLists]--><span style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:Symbol"><span>·<span style="font-style: normal; font-weight: normal; font-stretch: normal; font-size: 7pt; line-height: normal; font-family: "Times New Roman";">
</span></span></span><!--[endif]-->A current balun is required immediately after
the 4:1 balun.<span> </span>The OCF is not a
symmetrical antenna, so there will be rf current trying to go down the shield
portion of the feed line.</p>
<p class="ydp55647da7MsoNormal">If you want a good multipurpose antenna for the principal
ham bands this is a good starting point.<span>
</span>If you only have 66 feet of distance on your property, dividing the
numbers shown above by 2 will give you a 40M OCF.</p>
<p class="ydp55647da7MsoNormal">Thanks to Steve for starting this conversation.<span> </span>His was an interesting and in-depth analysis
of OCF dipoles.<span> </span>It got me to thinking
about my 80M OCF and how I needed to make the theory work at the K1VK qth.</p>
<p class="ydp55647da7MsoNormal">73 de K1VK</p>
<p class="ydp55647da7MsoNormal"><span> </span></p></div><br></div></div></body></html>_______________________________________________
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