Beware not putting the top yard inside small Teflon tubing. You will have an infinitely high Z at the top and potentially lots of KV. It will burn through the support line. 73 Clive GM3POI
-----Original Message----- From: Topband [mailto:[email protected]] On Behalf Of Richard Beerman Sent: 04 September 2018 17:18 To: Joe Subich, W4TV Cc: [email protected] Subject: Re: Topband: Air wound coil Rick and Bob, Thanks for such swift replies. Looks like I should try to reinforce the 3/8” tubing (it’s pretty short) with a wood dowel or perhaps with smaller or larger aluminum tubing. Then the fishing line method should be a perfect solution using 24 or 26 gauge wire. Using this method, I think a hairpin loop at the base of the vertical will help me achieve resonance. Thanks again. Dick W5AK > On Sep 4, 2018, at 11:36 AM, Richard Beerman <[email protected]> wrote: > > Top Banders, This discussion has been tremendously helpful to me as I also > am going to put a DX Engineering 68’ vertical when the QRN subsides here in > South Texas. Initially, I planned to install a large inductor (looks like it > came from a BC transmitter) that I found at a local hamfest. My calculation > is that this inductor has around 43 micro henries. According to various > contributors, this is not a good solution. I actually did the same back > around 1972 with a Hytower on 160 meters! It did work with a pathetic ground > system and 40-50 watts from a Ranger II. > > Anyway, here is my question…. my vertical has 3/8” tubing at the top. Pretty > flimsy to connect top loading wires except maybe small gauge wire. I am not > sure how well small gauge wire will handle voltages that may appear at the > top of a 68’ vertical. So, as an alternative, much like the Hytower does > today, what would happen if I installed top loading wires of a larger gauge > lower on the antenna where the tubing is more substantial? Any suggestions > regarding where the top loading could be connected on the vertical and > approximate length of the top loading wires? > > Thanks, Dick W5AK > >> On Sep 3, 2018, at 1:41 PM, Joe Subich, W4TV <[email protected]> wrote: >> >> >>> Getting to six would result in a smaller top hat but may not be >>> worth the mechanical hassle. >> If the mast has traditional three way guying, the mechanical hassle >> for a six wire top hat may not be that much greater than a four wire >> top hat. >> >> If the top hat wires slope downward, keeping them to the minimum >> length will result in maximum efficiency (and minimum "shielding" of >> the top of the vertical element). >> >> 73, >> >> ... Joe, W4TV >> >> >> On 2018-09-03 7:20 AM, Paul Christensen wrote: >>> I ran the same model in 4Nec2 as below but changed the hat from the >>> traditional two wires to four, spaced 90 degs. Complex base Z is near >>> 16+j0. Even though two symmetrical top-hat wires produce little radiation, >>> four wires result in wires that are only 24 ft long to achieve resonance -- >>> versus 41 ft with only two wires. Getting to six would result in a smaller >>> top hat but may not be worth the mechanical hassle. >>>> "4Nec2 shows that with a 68 ft. thin radiator, resonance can be achieved >>>> with wires roughly 41 ft. per side. With a ground field of 60 radials, 90 >>>> ft long on sandy ground, 4Nec2 reports a base impedance of 15.4+j2.5." >>> Paul, W9AC >> >> >> _________________ >> Topband Reflector Archives - http://www.contesting.com/_topband > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _________________ Topband Reflector Archives - http://www.contesting.com/_topband
