Nylon - Friend or Foe? - HomeBrew Forum at eHam.net

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eHam.net Forum : HomeBrew : Nylon - Friend or Foe?

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Nylon - Friend or Foe?	Reply
by KI6RKE on June 18, 2009	Mail this to a friend!
I'm building a quick 3 element yagi for 2m and the two pieces of copper pipe to be used for the driven element need to be insulated. I cannot find a phenolic insulator as called for in the plans and was going to use some nylon rod. Another ham said that he thought that nylon my not be a good RF insulator in the VHF and UHF bands. Is this true? David K6CDW

RE: Nylon - Friend or Foe?	Reply
by KB1LKR on June 18, 2009	Mail this to a friend!
Nylon tends to absorb moisture more than some polymers, that may contribute to poorer dielectric properties in a humid or wet environment and will lead to slight swelling. You might look at www.mcmaster.com for phenolic, PTFE, PE, PP, or other plastic rod materials too, or try some nylon and see how it works out, I'd guess it shouldn't be too bad however.

RE: Nylon - Friend or Foe?	Reply
by W5FYI on June 18, 2009	Mail this to a friend!
If you're using it to separate the two active elements at the current feed point, I'd certainly use it. At the current node, nylon would remain a good insulator, even at vhf. My only concern would be its durability; is it able to stand up to ultraviolet radiation well? I think some other plastics can outlast it, but covering it with vinyl tape will offer a great deal of u.v. protection.

RE: Nylon - Friend or Foe?	Reply
by KB6VIV on June 20, 2009	Mail this to a friend!
Do you have a Tap Plastics nearby? You can get acrylic rod there. UV won't affect it, low water absorbsion, a good strong economical plastic. They also have fiberglass rod, somewhat more expensive than Acrylic, not horrible. You can paint it for UV protection.

RE: Nylon - Friend or Foe?	Reply
by K4DPK on July 15, 2009	Mail this to a friend!
Avoid any pigmented plastics, especially the blacks and dark greys. These are often extrusion-pigmented with carbon black, which can break down at RF. If you're worried about whether a plastic material might be lossy, put it in the microwave for a 30 seconds and see if it gets warm. Heat would indicate lossiness. Nylon does absorb more moisture than other good plastic materials, by a factor of about 10X. The best all-around plastic I've found, in terms of heat and light stability, dielectric properties, machineablity and cost is Delrin. Teflon has slightly better dielectrics, but isn't as mechanically stable and it burrs badly when cutting and machining unless you keep it frozen while working. Phil C. Sr. k4dpk

RE: Nylon - Friend or Foe?	Reply
by WB6BYU on July 16, 2009	Mail this to a friend!
Nylon shouldn't be a problem in that application, except for the ultraviolet breakdown issues. It isn't as strong as some of the alternatives, either. At higher power levels, or at high impedance points, you may have more of a problem and I'd suggest using something else in those locations. Nylon is not a good choice for things like insulation in gamma match capacitors or a spacer near the top of the matching section of a J-pole. But the center insulator of a dipole has relatively low RF stress. (It can, however, have high mechanical stress.)

RE: Nylon - Friend or Foe?	Reply
by KE6WNH on July 16, 2009	Mail this to a friend!
I'd recommend acrylic aka polycarbonate for outdoor apps where UV exposure is inevitable. My experience with acrylic is that it's a rigid rather than a flexible plastic and it yellows over long exposure to sunlight, but as long as you fasten acrylic parts solidly, you should be fine on 2m. About the only drawback to acrylic is that you have to keep your cutting speeds very low to avoid gumming up your tools and stinking the place up. 73, Marty

RE: Nylon - Friend or Foe?	Reply
by KB6VIV on July 20, 2009	Mail this to a friend!
"I'd recommend acrylic aka polycarbonate for outdoor apps where UV exposure is inevitable." Acrylic IS NOT aka polycarbonate! These are two distinct plastics. Both have good UV resistance and are both available clear. FYI, Acrylic IS aka Plexiglass.

RE: Nylon - Friend or Foe?	Reply
by W1ITT on July 29, 2009	Mail this to a friend!
If you go to mcmaster.com , they have delrin rod in most any diameter you'd want (as well as all sorts of hardware and goodies). Price and service are excellent.

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