Ahh, so it is more complicated that I previously thought. Splitting/rotting bungee cords would certainy make them unsuitable for this application. The phrase "GEAR Resistance Shock Cord Assemblies" is something I hadn't heard of until I started googling around following the suggestion of using bungee cords. I presume the fancy title indicates that they are more expensive than run of the mill bungee cords. These particular items are intended for use in the bungee jumping industry; as in, human beings jumping from great heights and being saved from certain doom by these items. If that is truly the case then maybe these have more durability than the Chinese made Harbor Freight variety. I guess someone has to try them out to see if they are suitable for this application, any bungee jumpers out there willing to give it a go and report back your results?
On Sun, Sep 16, 2012 at 11:51 AM, Fred Townsend <ftowns...@sbcglobal.net>wrote: > Rick: > I too thought bungee cords the idea solution for hanging wire antennas. In > less than three months I had to redo the whole installation. My bungees had > cracks every centimeter or so. Finally one of the cracks parted completely. > I can't tell you the brand but was all black, made in China, and purchased > at Harbor Freight. I'm certain that uv did me in. > I saw a reference to Resistance shock. Can you explain the term? > They suggest the covered bungees (was that shocking pink or magenta?) help > with the uv problem but I'm thinking probably not with ozone, another known > rubber killer. Does anyone have experience with this or competitive > products? > 73 > Fred, AE6QL > > -----Original Message----- > From: elecraft-boun...@mailman.qth.net > [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Rick McClelland, > AA5S > Sent: Sunday, September 16, 2012 9:44 AM > To: gary bartlett > Cc: Elecraft List > Subject: Re: [Elecraft] FW: Question about suspending a delta loop... > > Gary, > > Your point about using bungee cords seems like a good idea. I've found > some > nice "GEAR Resistance Shock Cord Assemblies" on the Internet ( > http://www.adrenalindreams.com/gallery14.html) that seem like suitable > candidates. > > I must admit that I can't quite picture the manner that you are using the > tie wraps in your installation but it sounds like that arrangement is only > suitable for a vertically oriented delta loop as opposed to my horizontally > oriented loop. > > Rick > > > > > On Sun, Sep 16, 2012 at 10:05 AM, gary bartlett > <garybartl...@accesswave.ca>wrote: > > > I intended to post this here in case anyone else is playing with delta > > loops. It's a lot of wire in the air! > > > > 73, > > Gary VE1RGB > > > > -----Original Message----- > > From: gary bartlett [mailto:garybartl...@accesswave.ca] > > Sent: September 16, 2012 1:02 PM > > To: 'Rick McClelland, AA5S' > > Subject: RE: [Elecraft] Question about suspending a delta loop... > > > > Rick, I will describe what I have. Perhaps it will trigger something > > useful for you. > > > > I have a full-size 160M delta loop that is made from a single piece > > of that > > *Silky* jacketed wire which is wonderful around trees. It is routed > > over pulleys at the three corners, with the apex at a yardarm about 90 > > feet up a tower. The loop is roughly 75 feet per side, not a true > > delta shape. My antenna is fed to the radio using ladderline and > > operated multi-band through a 9:1 Guanella balun from 160M to 6M. > > It's buried in the woods. It's matched by the transmatch in my K3. I > > ignore the losses in the ladder line with CW. > > > > It is ordinarily fed as a loop at one corner although I am > > experimenting with what happens when one starts opening corners > > opposite to the feed point and feeding the antenna as some sort of > > irregular bipolar contraption. > > From > > the station I will soon be able to remotely reverse the feed points as > > well as open or close relays at will at the corners opposite to the > feeds. > > EZNEC > > suggests that I have a tonne of impressive lobes and low angles on > > some bands. While the delta loop is off the best heading by virtue of > > limitations on where I could hang it, I will at least be able to > > reverse the antenna patterns and see what that does for me. > > > > Up here we get freezing rain and high winds and ice build-up all at > > the same time, and is always a threat to wire antennas. Therefore I > > hang all my antennas with bungee cords wherever the haul down ropes or > > other means of securing the antenna are located. To this, at the most > > accessible point of the antenna suspension system, I add a tie-wrap as > > the final means of securing the bungee cord (and hence the antenna) at > > ground level. I call this a frangible fuse, I termed I robbed from > > working in aerospace. > > > > > > A physics guy can explain it better, but really big forces build up in > > the antenna if it takes a sudden shock. Something about overcoming > > resting inertia made sense to me when I read about it. Ballast is not > > a good idea up here. We need something compliant like the bungee > > cords everywhere there is an opportunity to fit them. > > > > If the bungee cord goes to the limits of its travel, it breaks the > > tie-wrap, allowing the antenna to gracefully sag to the ground and > > rest until I pull it up again and replace the tie wrap. I want my > > antennas to fall down without damage so I have built a deliberate > > failure point in the system at minimum walking distance from the station. > > > > I have paid the price from having antennas destroyed by weather but > > this method is nearly fool-proof and it has frequently been tested. No > antennas > > have been destroyed in this story. It doesn't matter what causes the > > sudden force on either of my wire antennas; if it is bad enough, it > > results in a graceful fall of the antenna wires to the trees below > > with its feedline intact and ready for quick return to service. > > > > 73, > > Gary VE1RGB > > > > -----Original Message----- > > From: elecraft-boun...@mailman.qth.net > > [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Rick > > McClelland, AA5S > > Sent: September 15, 2012 11:38 PM > > To: Elecraft Discussion List > > Subject: [Elecraft] Question about suspending a delta loop... > > > > I have a 240' delta loop suspended at three points about my QTH. I've > > been pondering adding another 47' but this is quite a challenge given > > the dimensions of my suburban lot. One thing I'm considering is to > > make good use of two trees located in a common area outside my > > property lines. Easily said, but I would not want to hang a 5 kg line > > ballast at either of these points because I can imagine a couple of > > neighbourhood youths scaling a tree with one of them cutting a line > > causing the 5kg weight to crash down upon the tender skull of the > > other youth. > > > > Legal matters notwithstanding, my question is whether I'm inviting > > certain mechanical failure if I fix the two endpoints outside my > > property lines and make use of only a single 5 kg ballast on the tree > > located within my property lines. The advantage of doing this is > > obvious, if any of the supporting lines outside my property are cut, > > the antenna falls onto my property and there is no possibility of > > injury to the perpetrators of the dastardly deed. > > > > As a possibly relevant aside, I don't use a typical insulator at each > > of the three suspension points. I use a 4" flat acrylic insulator with > two > 6" > > acrylic insulators attached to the end of the 4" insulator such that > > the resulting insulating apparatus appears to be a rather large 8" tuning > rod. > > In my non-mechanical-engineering mind, I imagine that having the > > insulator arranged in such a fashion reduces the peak tension at each > > apex of the triangle and also allows the wire to move more freely > > through the insulator without binding at that point. I realize that > > this matter isn't related to any Elecraft product but there are so > > many sage OMs here that I feel that an answer will be quickly forthcoming > and without controversy. > > > > -- > > Rick McClelland, AA5S > > Fort Collins, CO > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:Elecraft@mailman.qth.net > > > > This list hosted by: http://www.qsl.net Please help support this email > > list: http://www.qsl.net/donate.html > > > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:Elecraft@mailman.qth.net > > > > This list hosted by: http://www.qsl.net Please help support this email > > list: http://www.qsl.net/donate.html > > > > > > -- > Rick McClelland, AA5S > Fort Collins, CO > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > -- Rick McClelland, AA5S Fort Collins, CO ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
