Søren Kjærsgaard<p>My first <a href="https://techhub.social/tags/HB9CV" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>HB9CV</span></a> <a href="https://techhub.social/tags/antenna" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>antenna</span></a>, believe it or not, made from 5mm brake lines and a foot of 15mm copper pipe 🙂</p><p>I need it for a 70cm radio <a href="https://techhub.social/tags/foxhunt" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>foxhunt</span></a> event in a couple days - looked different places for design guidelines, some of them came up with quite different results 🤷🏼‍♂️🤨</p><p>Decided to just have go at it, based on a combination of what I could find in the legendary <a href="https://techhub.social/tags/Rothammel" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Rothammel</span></a> antenna book and some online sources and it turned out quite well 😃</p><p>Resonance is a bit low, 431MHz, but it’ll do fine as a direction finding device: what I really want is the characteristic kidney shaped radiation pattern, allowing me to turn the antenna backwards, looking for a minimum in the received signal. </p><p>Funny to see how the <a href="https://techhub.social/tags/smithchart" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>smithchart</span></a> impedance plot has a distinct turn at the resonance frequency 🤓</p><p><a href="https://techhub.social/tags/rfengineer" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>rfengineer</span></a> <a href="https://techhub.social/tags/hamr" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>hamr</span></a> <a href="https://techhub.social/tags/antennadesign" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>antennadesign</span></a> <a href="https://techhub.social/tags/testandmeasurement" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>testandmeasurement</span></a> <a href="https://techhub.social/tags/electronicsengineering" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>electronicsengineering</span></a></p>