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<blockquote data-quote="Rob Lancaster" data-source="post: 168053" data-attributes="member: 6154">Tony! After those bad tornados and thunder storms I was hoping they didn't find your body in the next county...&nbsp; <img src="/images/smilies/dizzy.gif"&nbsp; class="smilie" loading="lazy" alt=":dizzy:" title="Dizzy&nbsp; &nbsp; :dizzy:" data-shortname=":dizzy:" />Now that I finished the UVXB, we needed a tubing bender for our next project. It's a beam antenna that will operate in the VHS 162.400 to 162.550 MHz range.. It will have 11.7 dBd gain. It will sport a boom 13.2 feet long and use 10 elements. 8 directors, 1 reflector and 1 driven.. It's the driven element that needs to be bent on both sides. Hence the name, folded dipole.&nbsp; For the technically curious, have a look at the PDF.. That's what the math guy (bro Tom) came up with. He does the math and I take the specs from there and build and install it. That is, after we both go over the parts list carefully..&nbsp; We're almost ready to start ordering all the parts to build and mount it.This antenna will require a 4:1 balun as well; which we'll make. Over the years a bit of Tom rubs off and I've learned that you don't just hook up a coaxial cable to antenna any kine way.. If the transmission line is not impedance matched to the antenna all bets are off. The antenna won't radiate and damage in the final stages of the RF amps will occur if you try to transmit... And that's just for starters....The idea is to take an unbalanced 50 Ohm coaxial cable and match it with a balanced 200 Ohm folded dipole driven element.. That's where the balun comes in. Balun stands for balance unbalance.. A 4:1 balun will reduce the 200 Ohm antenna to 50 Ohms. A perfect match to the transmission line... Not only that the balun terminates the transmission line. In other words, the balun makes the transmission line know where to end and lets the antenna knows where to start on an electrical phasing level... If it's not terminated properly the first thing you'll notice is the transmission line radiating while testing. If it radiates all you have is a random length of wire for a antenna and that ain't cool!!Best thing I like about Tom,, he has the best in antenna tuning equipment! I'm talk'n Bird and MFJ. The antenna analyzers tell us everything we need to know to precisely tune these freaky things to the exact frequency/frequencies for maximum and safe performance...&nbsp; <img src="/images/smilies/bigok.gif"&nbsp; class="smilie" loading="lazy" alt=":twothumbsup:" title="Bigok&nbsp; &nbsp; :twothumbsup:" data-shortname=":twothumbsup:" />&nbsp; &nbsp; &nbsp; &nbsp;&nbsp; &nbsp; Are we having fun yet&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&nbsp; &nbsp; Answer; yes! On so many levels!! <img src="/images/smilies/applouse.png"&nbsp; class="smilie" loading="lazy" alt=":applouse:" title="Applouse&nbsp; &nbsp; :applouse:" data-shortname=":applouse:" />If anyone needs more; I know who to go to for more; so ask...……</blockquote>

[QUOTE="Rob Lancaster, post: 168053, member: 6154"] Tony! After those bad tornados and thunder storms I was hoping they didn't find your body in the next county... :dizzy: Now that I finished the UVXB, we needed a tubing bender for our next project. It's a beam antenna that will operate in the VHS 162.400 to 162.550 MHz range.. It will have 11.7 dBd gain. It will sport a boom 13.2 feet long and use 10 elements. 8 directors, 1 reflector and 1 driven.. It's the driven element that needs to be bent on both sides. Hence the name, folded dipole. For the technically curious, have a look at the PDF.. That's what the math guy (bro Tom) came up with. He does the math and I take the specs from there and build and install it. That is, after we both go over the parts list carefully.. We're almost ready to start ordering all the parts to build and mount it. This antenna will require a 4:1 balun as well; which we'll make. Over the years a bit of Tom rubs off and I've learned that you don't just hook up a coaxial cable to antenna any kine way.. If the transmission line is not impedance matched to the antenna all bets are off. The antenna won't radiate and damage in the final stages of the RF amps will occur if you try to transmit... And that's just for starters.... The idea is to take an unbalanced 50 Ohm coaxial cable and match it with a balanced 200 Ohm folded dipole driven element.. That's where the balun comes in. Balun stands for balance unbalance.. A 4:1 balun will reduce the 200 Ohm antenna to 50 Ohms. A perfect match to the transmission line... Not only that the balun terminates the transmission line. In other words, the balun makes the transmission line know where to end and lets the antenna knows where to start on an electrical phasing level... If it's not terminated properly the first thing you'll notice is the transmission line radiating while testing. If it radiates all you have is a random length of wire for a antenna and that ain't cool!! Best thing I like about Tom,, he has the best in antenna tuning equipment! I'm talk'n Bird and MFJ. The antenna analyzers tell us everything we need to know to precisely tune these freaky things to the exact frequency/frequencies for maximum and safe performance... :twothumbsup: Are we having fun yet>>>>>>>>>>> Answer; yes! On so many levels!! :applouse: If anyone needs more; I know who to go to for more; so ask...…… [/QUOTE]

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