Reception degradation with copper inside of PVC?

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Oldglide

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I'm thinking of building an OCFD dipole for outside use. To get the best results with the least amount of weight and ease of construction I was thinking of putting 1/2" copper tubing inside of 3/4" PVC. Do you think the PVC will have any effect on reception? I think not but I would like to hear it from others.
 

RadioDaze

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I have read reports that PVC can degrade with prolonged exposure to UV, eventually becoming brittle. (That's why it's not recommended for use as a mast.)

I'm curious as to whether the fact that vinyl contains lead (ironically, to help shield against UV) means that there are any RF shielding properties. But apparently a lot of antenna-building hams use PVC without a problem.

So, I too am interested in the answers to your question.
 

Krmit

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it is recommended to use 200 psi pvc and not Schedule 40. I don't remember the specifics as to why but you can get more info by googling Ed Fong or the DBJ-2 antenna.
 
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kb0nly

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The schedule 40 is thicker than the 200 or 125 psi pipe. I have used and compared them all. So the thinner variety means less plastic covering the antenna.

As for UV protection... You can paint the PVC, just make sure its a NON-Metallic paint. Even a coat or two of clear or plain primer is better than nothing to block the UV degradation. Don't use black. I know a lot of people like to for looks, but that just gets the antenna a lot hotter in the sun, and depending on climate where you live a black antenna can become brittle and fall apart faster also.
 

nanZor

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What it will do is change the resonant frequency of the antenna once you place it inside the pvc, so it is recommended that you tune the antenna once you get it inside the tube.

However, with an OCFD this isn't that critical. This is probably the only antenna you can pop inside a pvc tube and not get too worried about. :)
 

bejohnson

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You can test the PVC in question for RF transparency by placing a sample of the PVC and a cup of water into a microwave and heating the water. If the PVC warms any at all above the air temperature in the microwave it is absorbing RF energy and will introduce loss in the antenna system.
 

Alliance01TX

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PVC Antenna

Howdy

You also might research reviews and checkout "Ventenna" (see URL below). I have had one for several years that is the wide-band verson (scanning use only) and it works well. A bit pricicy, but you can see some ideas to utilize in your home-brew on a PCV like antenna.

I would look for 'black' pvc as it is normally better at handeling the UV rays...If you use grey or paint you will have a color issue in a year or two based on my expereince (Texas).

As with any antenna, the hieght, coax type (prefer low-loss), connectors and other factors (near man-made noise generation) are of concern. Also, you should seriously look at both static and lightning protection by using proper ground-rod(s) to offer higher level of protection to the Radio and-or the structure if mounting on a roof. I used a simple tripod with a home-brew 4' lennght of pvc & had my Ventenna slipped into the pvc extenstion....and well grounded. So about an effetive height of 10' (tripod, pvc extenstion & Ventenna) and that was the limit I would say is safe (10' max) to use in my opinion....

Hope this helps and let us know what you create!

Thx

Bill


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Kennrth

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Because I can't trust what they put in things these days like contaminated dry wall from China as well as lead paint on toys. I like the pvc microwave trick. Should work with just about anything. I noticed some of my ceramic mugs get hotter then others. Nothing like emperical evidence for good decision making. Manufacturers of modern PVC add metalic salts to make it flexible and stand up to ultraviolet light. Testing it would be a good idea.
 
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