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UHMW Polyethylene as spreaders




 
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Author Topic: UHMW Polyethylene as spreaders  (Read 6250 times)
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WA1LGQ
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« on: February 26, 2005, 06:37:04 PM »

Does anyone know how UHMW Polyethylene would do as antenna feedline spreader material? I have come across some strips of this stuff that would be easy to fabricate into spreaders if its any good. How does this do around rf? How will it hold up over time exposed to the elements? Will it cancel out slopbucket signals? Anybody know?          Thanks............Larry
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WA1GFZ
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« Reply #1 on: February 26, 2005, 07:33:36 PM »

Larry,
I think that is  the same stuff you find in coax dielectric but it may have
problems with UV. Home depot sells fiberglass rod as driveway markers
for about $3 each and are 4 feet long. 16 4 inch spreaders for $3 sounds cheap enough. gfz
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W1JS
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« Reply #2 on: February 26, 2005, 08:43:35 PM »

Quote
Home depot sells fiberglass rod as driveway markers


Damn! And I have been actually using them as driveway markers to keep the kids' cars out of my wife's flowers and to guide the snow blower during the winter.  There might be a few missing this spring...
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73 de
W1JS
Jack
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KL7OF
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« Reply #3 on: February 26, 2005, 08:52:50 PM »

Put a chunk of it in the microwave oven to test for rf........
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KB1KFI
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« Reply #4 on: February 26, 2005, 11:49:12 PM »

You're in a good place with using....'found' materials',
it should work just fine, as long as you have the spacing according to the formular...diameter of the wire and the spacing controling impedance...
K1KFI
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Ed KB1HVS
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« Reply #5 on: February 27, 2005, 06:37:32 AM »

Quote from: KL7OF
Put a chunk of it in the microwave oven to test for rf........

 And what do you tell the XYL if the test fails? :oops:
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Jack-KA3ZLR-
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« Reply #6 on: February 27, 2005, 06:39:07 AM »

:lol: RUN..........LOL..Duck and Cover...
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N8YE
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« Reply #7 on: February 27, 2005, 09:50:36 AM »

:cool: I use those fiberglass rods also. I buy 12/2 or 12/3 romex wire and strip it out for the feeders. Does it matter if one strips out the wire to the bare copper? What would happen if the white and black plastic cover is left on the copper? Which is better, stranded or bare?
Thanks...Steve..N8YE
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N9NEO
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« Reply #8 on: February 27, 2005, 01:04:38 PM »

Frank,

How exactly do you have to cut a 4' piece of the stuff to get 16 4" pieces?  I'm having probs with the math.  

Fiberglass is good stuff.  I have a compound bow made of it, and also an automobile body.  They both work very well, so I'm sure you can also use it for transmission line spacers.

73
NEO
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WA1LGQ
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« Reply #9 on: March 01, 2005, 05:21:16 PM »

Ok, I tried the microwave oven test on a piece of the stuff, and it did not get warm. Not sure if this applies to HF freqs, but intuitively it makes sense. I will check out the fiberglass driveway markers, I would think that fiberglass will hold up better, but am not sure about that really. Anyone have an answer to Steve's question about whats better; stranded or solid wire? Thanks for the help.............Larry
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K1JJ
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"Let's go hiking in the woods, Tommy!" - Yaz


« Reply #10 on: March 01, 2005, 06:02:21 PM »

Quote from: WA1LGQ
Anyone have an answer to Steve's question about whats better; stranded or solid wire? Thanks for the help.............Larry


Hi L,

I spent some time talking with a guru who used open wire to inter-connect his massive 450mhz Yagi array. It works very well for him. (see another post I made a month ago)

He said that on VHF/UHF you don't want to use bare copper cuz of the surface corrosion and poor conductivity due to skin effect. On VHF+ the RF currents would be flowing mostly on the surface thru this crud.

But, on HF, the penetration is deeper into the copper wire and the surface crud becomes a smaller percentage of the path.  On 160-40M I wud think it's a non issue, though it's all a matter of degree and how anal you are.

He suggested using double coated enameled wire for the feeders to keep the copper clean inside. You might also wonder about using the common PVC covered wire. Evidently there are dieletric losses using that above 20M or so, but again, 160-40M should be OK and a matter of degree. I've used it for years on HF.

As for stranded or solid, it makes no difference on HF, though he recommended to use solid on VHF/UHF for whatever reason. Maybe cuz enamaeled wire is usually solid or maybe solid is smoother for RF skin effect, dunno. (that almost sounds like an audiophile oxy-free type comment, huh?  :-))

I've used simple PVC tubing, the gray 1" diameter gray stuff in the electrical dept at Home Depot for speaders right up to 20M.  Cut them into 5-6" lengths, drill holes and slip them onto the pair of wires. Stretch the open line out TIGHT between two trees and then tie the spreaders on with #14 SOLID insulated copper wire.  I usually use PVC covered black #10 stranded wire for both feeders and flat top on HF.  (Home Depot, 500' roll - cheap)

Those fiberglass reflector sign rods are FB too. I've used them for Yagi center el sleeves on 6M.      Most any good insulator material is OK on HF as long as it is UV resistant. Watch out for some nylon stock that turns to mush in the sun. Also, paint the ends of your fiberglass rods to keep water from wicking in. Once the outside glaze is broken it becomes vunerable according to a fiberglass guy I know.

73,
Tom, K1JJ
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WA1GFZ
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« Reply #11 on: March 01, 2005, 09:42:16 PM »

Bob,
heard the story of bread and fishes? Well that isn't me so you only get
12 spreaders da. Joe PJP came up with the idea.
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WA1GFZ
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« Reply #12 on: March 01, 2005, 09:45:38 PM »

Tom, have you visited Frank the Fiberglass guy recently?
We just bought some cool 2X4 inch tube for our new emi room
at work.
Looks like cool stuff.
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