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Antenna Building Materials
Hello: Now that Spring has arrived I am getting the urge to rebuild and/or add antennae to my backyard landscape. I seem to recall an article in QST that showed use of 1/4 inch diameter PVC tubing as spacers in a fanned dipole array. However, Home Depot does not have that size available. Where can 1/4 inch PVC tubing be purchased w/o goiong through an OnLine source ? Does anyone remember which issue that article appeared ? I would think that spacers used with open transmission line would also work in my application of a fanned dipole array. So, from where can spacers be obtained or homebrewed ? TNX. 73, de ~ Vince ~ WA2RSX Stuck on IOTA NA-026 |
Vince wrote:
I would think that spacers used with open transmission line would also work in my application of a fanned dipole array. So, from where can spacers be obtained or homebrewed ? The black plastic irrigation tubing is what I use. It's very easy with which to work. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Vince wrote: Hello: Now that Spring has arrived I am getting the urge to rebuild and/or add antennae to my backyard landscape. I seem to recall an article in QST that showed use of 1/4 inch diameter PVC tubing as spacers in a fanned dipole array. However, Home Depot does not have that size available. Where can 1/4 inch PVC tubing be purchased w/o goiong through an OnLine source ? Does anyone remember which issue that article appeared ? I would think that spacers used with open transmission line would also work in my application of a fanned dipole array. So, from where can spacers be obtained or homebrewed ? Forget Home Depot, get familiar with the Mother of All Hardware Stores. Go to: http://www.mcmaster.com/ In the search box in the upper left corner enter "9446K41" and go. Also check out #87025K27. Although it's heavier and a bit more expensive I'd use this PVC Type 2 solid rod stock which is an electrical grade PVC. It's much stiffer and stronger than the tubing and it comes in straight lengths rather than being wound in a coil. I wouldn't worry about the "use indoors" comment, the stuff will last for years out in the WX. Or spray paint the spreaders black. TNX. 73, de ~ Vince ~ WA2RSX Stuck on IOTA NA-026 w3rv .. . stuck . . |
Somewhere, I read that the black plastic and grey conduit types were
unsuitable for antenna construction. And, if I remember correctly, it was (claimed) due to carbon in the black and metal oxide coloring in the grey... Was this an old wives-tale? Regards, John |
John Smith wrote:
Somewhere, I read that the black plastic and grey conduit types were unsuitable for antenna construction. And, if I remember correctly, it was (claimed) due to carbon in the black and metal oxide coloring in the grey... Was this an old wives-tale? The thin plastic irrigation tubing has close to infinite resistance and stays cool in the microwave. It is used as spacers in presently available open-wire transmission line. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
John Smith wrote:
Somewhere, I read that the black plastic and grey conduit types were unsuitable for antenna construction. And, if I remember correctly, it was (claimed) due to carbon in the black and metal oxide coloring in the grey... Was this an old wives-tale? Regards, John It is correct , normally testing the conduit in a microwave for 30 seconds works , if its not hot then its reasonably rf resistant . |
Cecil Moore wrote: John Smith wrote: Somewhere, I read that the black plastic and grey conduit types were unsuitable for antenna construction. And, if I remember correctly, it was (claimed) due to carbon in the black and metal oxide coloring in the grey... Was this an old wives-tale? The thin plastic irrigation tubing has close to infinite resistance and stays cool in the microwave. It is used as spacers in presently available open-wire transmission line. Cecil, who sells that line?? -- 73, Cecil http://www.qsl.net/w5dxp w3rv ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Thanks Cecil/Atec... I have expanded my list of antenna materials! And, the
microwave will be my authority... Warmest regards, John |
Brian Kelly wrote:
Cecil, who sells that line?? http://www.w7fg.com -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
On Wed, 27 Apr 2005 18:01:30 -0500, Cecil Moore
wrote: John Smith wrote: Somewhere, I read that the black plastic and grey conduit types were unsuitable for antenna construction. And, if I remember correctly, it was (claimed) due to carbon in the black and metal oxide coloring in the grey... Was this an old wives-tale? The thin plastic irrigation tubing has close to infinite resistance and stays cool in the microwave. It is used as spacers in presently available open-wire transmission line. At work we had an issue with the use of nylong tie-straps on our test fixtures that were used during RF testing (moderate power, Ka band). Well, I'm in the mechanical side of the house but suggested the microwave test & pretty soon I was surrounded by RF guys who heard about my answer and were interested in why I thought that would work - when I explained it they were not only satisfied it would answer their concern but were rather impressed that a guy who does mechanical ground support equipment came up with it. None of them were Hams. I think it's great that our hobby can help us out in other ways. Howard |
Jim Higgins wrote:
On Wed, 27 Apr 2005 17:23:33 -0700, in , "John Smith" wrote: Thanks Cecil/Atec... I have expanded my list of antenna materials! And, the microwave will be my authority... You might want to remember to put about a cup of water - or half a cup at least - into the microwave along with whatever you test to avoid possible problems with pumping power into an unloaded cavity. Every microwave instruction manual I've ever seen warns about running them empty, and a lot of unaffected material like PVC tubing is the same as empty. Because the inside of the oven tends to get warm and steamy, everything tends to warm up a little. It's best to compare the material you're testing against samples of known good materials like PTFE, polyethylene (the insulator from RG214) or a hot-melt glue stick. The regular translucent hot-melt glue material (amorphous polypropylene) is also an excellent RF insulator. It's useful for all kinds of antenna building and weather-sealing. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Actually, I have a set of "dummy loads" for microwave ovens, don't remember
where I picked 'em up at (gov't auction?)... they seem to be silicone rubber??? impregnated with some kind of conducting material (carbon? Metal oxide?) You surely must be able to get 'em from a "microwave tech?" You can even use a thermometer in them, "nuke" for a certain time and arrive at different measurements--mainly power output.... I am sure some here have seen these things and can describe them much better than I.... But, the smaller ones work perfect for my "microwave experiments" (ever chuck a fly in a bottle and see how long it lives in microwave environment?) (chuck a BIG one of these dummy loads in, and the oven won't even warm a glass of water, or seemingly, harm a fly!!!) Regards, John |
John Smith wrote: Thanks Cecil/Atec... I have expanded my list of antenna materials! And, the microwave will be my authority... You might wind up throwing the baby out with the washwater. Somebody somewhere once pointed out to me that many materials have different resistivities at different frequencies, the higher the frequency the lower the bulk resistance. One implication being that a candidate spreader material which gets hot in a 2 Ghz microwave oven does not necessarily mean it will be at all lossy at 7 Mhz. The FCC human RF exposure limits rules are based in this principle. Being a few feet away from an antenna radiating 100W of 40M RF is not a problem, 100W of 2 Ghz RF into the same antenna is deadly or close to it, etc. About a year ago I picked up some 2"-3" scrap lengths of carbon fiber composite hunting arrow shafts from a local sporting goods store and put them to the microwave test. This material has an extremely high strength/weight ratio which makes it attractive for use as spreaders. They got pretty warm after nuking them for five or so minutes. Then I checked several of them with my DMM set to it's 200 megohm range. In all cases the DMM indicated completely open circuits. From this experiment I've concluded that this material is plenty "good enough" to use for HF feedline spreaders. Unfortunately it's a bit difficult to drill & cut. Warmest regards, John w3rv |
Cecil Moore wrote: Brian Kelly wrote: Cecil, who sells that line?? http://www.w7fg.com I've wondered what he's using. Tnx Cecil. 73, Cecil http://www.qsl.net/w5dxp w3rv ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
On 28 Apr 2005 10:23:55 -0700, "Brian Kelly" wrote:
Cecil Moore wrote: Brian Kelly wrote: Cecil, who sells that line?? http://www.w7fg.com I've wondered what he's using. It's 1/2" pipe, rated for 100 PSI in its original use; looks sturdy... bob k5qwg Tnx Cecil. 73, Cecil http://www.qsl.net/w5dxp w3rv ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
any pnumatics supplyer will sell you 6mm 8 mm 10mm diameter tubing in both
pvc and poly prop in long lenghts and you can cut it down i paid about £10 or $20 or so for 30 mts of the stuff today chop it with a pipe slice into the lenght you need hope this helps dave |
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