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## Re: [TowerTalk] 43ft Vertical Feeding Question and Balun type,

 To: towertalk@contesting.com Re: [TowerTalk] 43ft Vertical Feeding Question and Balun type, "Dan Zimmerman N3OX" Thu, 20 Nov 2008 17:26:21 -0500 mailto:towertalk@contesting.com>
 ```>What happens if we take the N3OX approach, but put two, or possibly three >wires going up the outside of the fiberglass, If you work it right, you should be able to get a good parallel vertical going that way. I've seen it done a few times with fairly long standoffs to the sides. It would be tough to do with wires wrapped tight around the pole ;-) You might need to detune/ground/lift some wires for various band combinations to avoid high angle radiation, like if you had a 15m element and a 40m element, you'd have to detune the 40m one to avoid it radiating like a 3/4 wave vertical. But if you *did* have a 66 foot vertical that you wanted to use on 15m, you could drive the 66 foot element and the 1/4 wave wire *differentially,* like a J-pole. I chose the simplest approach for me: base matching on 160m through 30m, because I didn't care about 20m and up on my 60 foot antenna (because of radiation angle problems and the fact that I had other antennas) When I built the 40 foot antenna originally, I never actually had the 20m matching network installed, but figured I'd run the numbers and toss it in there because the antenna works well on 20. But I've got the tools to design networks, it' s just EZNEC to model the impedances, one of any number of tools to calculate the right L network, some junkbox capacitors and home-wound coils. I use some of the late G4FGQ's programs (archived at zerobeat.net) to calculate the right values of inductance and capacitance, and also to calculate the physical dimensions of air wound coils from ordinary house wire with the insulation stripped. It helps that I have a lathe to make coil forms on ;-) Others who don't want to go through that stuff can certainly go the parallel vertical route, trading element mechanical complexity for electrical simplicity. - - -- - - Or you can just accept some extra loss and use a tuner in the shack for the ultimate in simplicity, and that's what's causing these things to sell like hotcakes. There are a lot of bands where a 43' vertical with the right balun and a short run of low intrinsic loss coax to a good tuner isn't going to be so bad, and others where it will be terrible. With the right transformer in the "typical" installation of maybe a few dozen feet of RG-213 to a tuner, the losses on the bands 40m and up tend to stay under 3 or 4dB, maybe 5dB if your coax run is long. On some bands in pretty typical installations, you'll get within 1dB of what would happen if you went to the trouble of base matching the thing! But the eHam thread shows the danger of not understanding the antenna system. It seems like a popular 43 footer and feedpoint transformer combination actually drives the coax shield quite high in voltage, and depending on the completion of the coax shield common mode circuit could cause HUGE problems in performance. For other users it will cause very few problems. " Is 43 feet some magic length?" It's not close to half-wave resonant on any band. Probably gets closest on 30m, but it's still three feet off there. So the feedpoint voltage is moderate across the bands, and the SWR is not horrific until you get below 40m. SWR runs <6:1 w.r.t. 200 ohms across all of HF until you get down to 80m. Electrically, maybe it's an exercise in calculated mediocrity ;-) But I think I have a theory why people love these things so much. They're very simple to install, very simple to maintain, they have no adjustments at all, score one. The original, at least, is gorgeously made and quite impressive looking. People bust pileups better when they feel good about their antenna. Score two. They tend to be sold as massive flamethrowers of an antenna that will give you a big signal, and they're expensive for what they are. I think this convinces people thoroughly that they need to not screw up this awesome antenna by not laying down enough radial field and by using cheap coax. So people buy their big gun 43 foot vertical and then they back it up with 8200 feet of radial wire and spring for LMR-600 coax for the feeder, and the \$180 balun with a core sized for a shortwave broadcast station. This replaces their Butternut on a ground rod fed with ratty RG-58. That's the hat trick. Of course they're happy ;-) The fancy 43 foot antenna inspires people, finally, to crawl around on the yard for a day stapling down miles of copper and to replace their 20 year old coax with hardline. Whether or not you can pick up 3dB on the average band (much more on 80/160) if you stamp out the line loss hardly matters. I think people like these things because they find them to be WAY BETTER than the thing they replaced. A lot of that probably has to do with the rest of the installation, but there you go. 73 Dan _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread Re: [TowerTalk] 43ft Vertical Feeding Question and Balun type,, Rob Atkinson Re: [TowerTalk] 43ft Vertical Feeding Question and Balun type,, Art Trampler Re: [TowerTalk] 43ft Vertical Feeding Question and Balun type,, Dan Zimmerman N3OX <=