Which PVC to use for a feed point on dipole? Is ugly balun needed?

[Alan Blackmon]

I asked by friend Google but there was no response that made the answer clear. I do see photos and write ups of those who have built fan dipoles or dipoles in general and they were white or gray. Now I have so much of the black PVC but no white in the 4 inch size. I collected it for making ports in DIY speakers so there is quite a bit of it around in my garage.

I want to make a 80m inverted V dipole and wonder if the black would be alright to use or am I seeing white and gray only due to black should not be used for some reason I have not heard yet? I know that black does have some metallic properties and it will heat up if you put it in the microwave where white PVC will not heat. So should I avoid making the feed point of a dipole out of black PVC? I want to make a 80 meter plus other bands inverted V. Thanks.

While I am at it another question if I may. Those who have put up dipoles did you or did you not include a ugly balun at the feed point? I have asked my buddy Google about that and is seems many have and a few have not. I am willing to do so but if it isn't really needed it sure will make building the feed point easier.

 

[Redbeard U812]

Ya know, I have never had a desire to cook PVC and I find it interesting that the white PVC won't heat. The grey is obviously used in electrical conduit, and they say don't use white. Although we have done that. Did not realize that black has metallic properties, I have fused the stuff used in process piping 4" thru 28" at chemical plants. It was used due to affordability, easy install, it's non-conductive properties. Mostly underground through units from cooling towers.

If it has enough metallic in it, it may effect things. It may not. I wouldn't wrap coax around metal to form a balun.

 

[wavrider]

It is an antenna, nothing fancy about it, Do not over think it, use what you have laying around, I do not think any of the PVC is conductive,
Ugly balun wont hurt and may keep your neighbors happy by reducing or eliminating CMC on the feed line.

 

[BJ radionut]

https://www.dxengineering.com/parts/dxe-uwa8x-kit
Makes the Job easy.

Also "SOME" black PVC tubing can have higher content of Graphite or Carbon(for color)...most generally is not a factor(unless wet or as Sunlight exposure begins to brake it down),
but you said 4 inch (?)
Using this size for a dipole adds a bunch of extra weight, you don't need in your build IMHO.
I have used gray (3/4) or 1 inch for center insulator(3-6 inches long) and use 1/2" couplings for ends with no issues(cheap Home Depot/Lowes stuff)…
Good luck Alan, many here to help
All the Best
Gary

PS: I have used several of DXE dipole kits...they work Great!...And they last!
Have built with/without balun … never seen much difference.

 

[Captain Kilowatt]

Put a piece of PVC and a cup of water in the microwave for a minute or two. If the PVC gets hot don't use it. If it remains cool while only the water gets hot it is fine to use for baluns or choke cores.

 

[Alan Blackmon]

Thanks all for your replies. I don't know for certain about the metallic properties but I do know that in some of the antenna DIY sites that it was said DO NOT use black PVC to build antennas inside of. Use the white. Now I can't recall exactly why but my old brain goes to the metallic properties. Carbon as mentioned above may actually be the culprit.

Why 4 inch? One builder used that size due to his hands being able to get inside to build a feed point for a four band fan dipole. I have a project in mind for such a build.

 

[Captain Kilowatt]

It has nothing to do with metallic composition. It is the carbon used in the colouring that is the culprit.

 

[sp5it]

For 80m air wound choke balun is bad idea because of low performance on 80m.
Better, lightweight option is 16-18 turns of coax on FT240-43 core(s). Like that:

Mike

 

[Shockwave]

Put a piece of PVC and a cup of water in the microwave for a minute or two. If the PVC gets hot don't use it. If it remains cool while only the water gets hot it is fine to use for baluns or choke cores.

I've always been fond of the microwave oven test on materials used with RF. Nothing new there but... the water is one of the best additions to this test that I've ever heard. I've melted more than one important part that failed this high power test but that part could have easily been used in a lower power application had it not melted in the microwave first.

 

[Captain Kilowatt]

I've always been fond of the microwave oven test on materials used with RF. Nothing new there but... the water is one of the best additions to this test that I've ever heard. I've melted more than one important part that failed this high power test but that part could have easily been used in a lower power application had it not melted in the microwave first.

The water is to give the oven a load. Microwave ovens should NOT be run when empty of anything that will not absorb the radiation.

 

[Shockwave]

That's true too but the added benefit is I don't have to explain why the kitchen and microwave smell like melted plastic anymore.

 

[arc1]

There are many other choices of plastics that you could use for this application other than pvc. If you're that serious about it, the properties you have to consider are good electrical insulation (obviously), strength, moisture absorption, temperature (extreme climates) and UV stability. This is where it can be tricky, black type plastics often have carbon in them, as you know. Whether this is going to affect things?? This is the conundrum, do your research, Teflon is pretty good I think. As far as the messy balun thing, I'd be thinking at least a decent ferrite choke or 1:1 balun.

 

[oldtymer]

I have always used schedule 80 the dark grey type used for high pressure fluid installs.
Holds up to uv better also not conductive.
Also due to the thickness of the walls it is a better fit to standard diameter aluminum
tubing.

 

[543_Dallas]

I don't think you'll have an issue with any type of pvc at 3 to 4 mhz. As said a ferrite core choke would be more effective and smaller.

Avoid coax with a foam dielectric. The center conductor will be more likely to drift and screw up the impedance of the coax. Whatever you use look at the spec sheet for the minimum bend radius.

http://www.karinya.net/g3txq/chokes/