Best Plastics, Composites, Rubber for structural antenna parts

90338 Views 212 Replies 43 Participants Last post by 300ohm, Oct 10, 2013

stampeder

Discussion Starter · Nov 26, 2008 (Edited)

Just a warning note about using ABS for structural parts that I've mentioned many times before - hopefully what you're planning to use is the thick walled stuff that has little or no flex. If you go to Rona or Lowe's or Home Depot and shake a 10 foot ABS pipe like a sword it flexes a lot.

It seems to be rigid, but its not. If you shake a length of PVC like that it will seem like a wet noodle, so avoid using PVC for structural use either, except when recommended in build plans.

From experience I'm clarifying that ABS should never be used as a pole or mast, and it should be carefully considered if you're thinking of using it as a horizontal boom of any length more than a meter or a few feet.

81 - 100 of 213 Posts

DdDave

· #81 · Jul 23, 2009

Is that CPVC?

Yes, at the start of the build the only material I could find with all of the proper fittings was plambing CPVC. Half way through I found another store that carries electrical PVC and PVC fittings (T's, 90's, etc...) that probably would have saved me about $10-$15 on the build.

Would it also be possible to drill holes through the plastic frame and put both the reflector rods through it as well as the 1/4" ID supports?

It's possible, but the small white tubes in the middle are used to set the gap spacing, so it would be more difficult to do this through the tubes, and I wanted to minimize the amount of holes in the main tubes to keep the frame strong. I also wanted to be able to take the antenna apart easily while I was experimenting with it, by loosening the screws on the outer cable clamps I can disassemble the whole antenna quickly and put it back together in the exactly the same. Going through the frame tubes would also need some other way to secure the tubes side-to-side.

What gauge wire are you using for the zigzag

10ga, but last time I was in the states I picked up some 8ga for my next build. This antenna's been outside for about a month now and survived a few heavy storms with no issues.

What is holding the outer part of the reflectors, wire ties ?

I used 1/4" cable clamps, the ones that look are shaped like a "p" (or "b", or "d", depending how you look at it).

Did she say if it was UV resistant or not ? If not, I would spray paint it with a thin covering coat for outdoor use. I personally wouldnt spray paint the driven element though.

She didn't say, but I assumed it wasn't so I took off all the copper and gave everything a nice flat black finish.

Here's a closer picture showing how the reflectors are assembled. The white tube in the middle of the reflectors actually has 2 turns of electrical tape around it to give the 3/8" cable clamp a nice snug fit, without the tape it was a bit too easy to slide side-to-side.

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Schmerm

· #82 · Jul 29, 2009

Any tips on straightening that #10 wire before making it into a zigzag?

Also, going back to PVC-related discussion, my fittings arrived this week. Everything is 1/2". I noticed that when putting conduit into the fittings that it inserts 3/4" when it goes in all the way, as far as it will allow. Is this normal? I remember 300ohm's instructions with 1/2" sch40 pvc fittings said to insert everything 5/16", so maybe one is not supposed to insert things all the way in? And if so, why 5/16" and not some other arbitrary amount?

I do notice that when fitting all the way it sometimes takes effort (and possibly lubrication may be in order). Is this why it's not a good idea to insert the tube all the way into the fittings?

johnpost

· #83 · Jul 29, 2009

Schmerm said:
Any tips on straightening that #10 wire before making it into a zigzag?

thread

Wire Straightening Tricks For Antenna Builds

is at

http://www.digitalhome.ca/forum/showthread.php?t=100636

DdDave

· #84 · Jul 29, 2009

I noticed that when putting conduit into the fittings that it inserts 3/4"

All of my fittings also went in 3/4". I would think you would want to bottom everything out so you could dry fit it and possibly take it apart if you want to make slight changes as you progress through the build, and you want everything to go back the exact same way. Not sure about the 5/16", maybe other brands of fittings have different stop depths.

and possibly lubrication may be in order

Don't use lube, because if it's easy to go in, it's easy to come back out when you don't want it too. It may also interfere with the glue if you plan on gluing it all together when you are done. Just give a bit of a twist as you insert it and it should bottom out easily.

johnpost

· #85 · Jul 29, 2009 (Edited)

Schmerm said:
Also, going back to PVC-related discussion, my fittings arrived this week. Everything is 1/2". I noticed that when putting conduit into the fittings that it inserts 3/4" when it goes in all the way, as far as it will allow. Is this normal? I remember 300ohm's instructions with 1/2" sch40 pvc fittings said to insert everything 5/16", so maybe one is not supposed to insert things all the way in? And if so, why 5/16" and not some other arbitrary amount?

I do notice that when fitting all the way it sometimes takes effort (and possibly lubrication may be in order). Is this why it's not a good idea to insert the tube all the way into the fittings?

3/4" depth is normal for that size fitting.

300ohm dry fastens with a bolt when finished so all of the strength of the joint isn't from overlap as would be with gluing. leaving some additional depth allows for adjustments if needed during assembly.

the fittings are designed to be glued (solvent welded for these plastics) which requires lots of very close contact, so it is very hard to insert fully sometimes when dry fitting. with glue on it acts as a lubricant and it will slip all the way in most of the time with moderate force and a twist.

if you cut all the pieces to fit with full insertion then if any are not fully inserted or pieces not cut square it will cause that joint to be larger. by the end of a total assembly your outside dimensions, which is where the wire is, may be off. so leaving some play allows adjusting joints for a final good result. as you assemble mark the outside of each piece with pencil to show the insertion depth needed.

using for intended purposes of plumbing or conduit may require full insertion. also often when doing those tasks you measure, cut and glue individual pieces and so adjust as you go along. when making structures like antennas or furniture you have to modify construction methods sometimes.

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300ohm

· #86 · Jul 29, 2009

300ohm dry fastens with a bolt when finished

Nope, just a single #4 X 3/8" or 1/2" wood screw. It holds it well enough. A pop-rivet is another possibility.

Schmerm

· #87 · Jul 29, 2009

Cool, thanks guys. I have the wood screws from the parts list for the meshed GH, along with PVC cement, so I might partially insert to 1/2" and use those to keep it in place.

stampeder

Discussion Starter · #88 · Aug 6, 2009

Nylon nuts and bolts in the Plumbing section

Some toilet seat bracket nuts/bolts are fairly lengthy and made of nylon, so if you can get used to the backwards threading on some of them I think they'd be a good option for someone needing non-metallic joiners for antenna building. I have no idea if they're UV-resistant though.

300ohm

· #89 · Aug 6, 2009

I have no idea if they're UV-resistant though.

Nope, not UV resistant. They would have to be painted or protected from the sun in some way.

johnpost

· #90 · Aug 6, 2009

stampeder said:
Some toilet seat bracket nuts/bolts are fairly lengthy and made of nylon, so if you can get used to the backwards threading on some of them I think they'd be a good option for someone needing non-metallic joiners for antenna building. I have no idea if they're UV-resistant though.

nylon is also very slippery (self lubrication) and deformable (it will stretch).

so you may need to use thread locking to count on some degree of tightness. because it might stretch you might never get real tightness before the bolt fractures.

balm

· #91 · Aug 6, 2009

Some toilet seat bracket nuts/bolts are fairly lengthy and made of nylon, so if you can get used to the backwards threading on some of them I think they'd be a good option for someone needing non-metallic joiners for antenna building. I have no idea if they're UV-resistant though.

been there, done that...they dont work...dont waste your money & time...you will have to buy a toilet accessory kit just to get a couple screws if you cant buy them individually (which is the case in Montreal at least!).

And when you tighten them they dont get tight...same thing for license plate fasteners, they dont work....

BTW, toilet fasteners are NOT UV, whereas license plate fasteners ARE UV..

stampeder

Discussion Starter · #92 · Aug 6, 2009

balm said:
license plate fasteners

That's an interesting possibility, but they're not very long though.

300ohm

· #93 · Aug 6, 2009

whereas license plate fasteners ARE UV..

Yeah, forgot about those. So are marine nylon (Derlin ?) nuts and bolts, but pricey.

balm

· #94 · Aug 6, 2009

the plate fastners can be up to and more than 1" sometimes...but they dont tighten, they ONLY FASTEN (big difference!), also at close to $2 a screw - a real rip-off...

as for marine derlin, thats a no-find here in Montreal....no surprise...ironical considering we are SURROUNDED by marine!

Schmerm

· #95 · Aug 22, 2009

When gluing PVC, is it absolutely necessary to use cleaner/primer first? I did a test fit with a scrap piece of pvc and a scrap part-of-a-T-fitting, just to see what would happen if I used PVC cement on them (this is my first time working with PVC), and when the gunk dried it seemed to hold together well (but my senses could be deceiving me).

loveota

· #96 · Jan 5, 2010

Durability of rubber grommets for reflector mounts on GH?

Perfect for testing the durability of our creations.
2 weeks ago we put a gapless GH10 on a 30' tower my brother had open. My only concern is that i used rubber gromets to hold the reflectors in the mast. As of now the reflectors are held inplace very well with them but not far down the road they`ll become a problem. My questions to this would be : if i drilled the reflector holes in the mast to the size or slightly smaller than the 1/4" rods used , eliminating the gromets , is there a certain cement that would adhere a steel mast with aluminum rods ? Would the contact of the reflectors and the mast affect the performance of the reflectors ? I`m after the simplest and cheapest build with this design but it has to last. I think i have 2 of the 3.
The performance of this GH is very good . Slightly weaker than my XG but its now abit closer to the target stations in Erie. Unpowered, 3 Erie stations came in around 80% . 2 ch were unobtainable . About 60' of rg6 was used . Only a static discharge block in the line to the tv. We put in a Wineguard 8275 pre-amp and that brought the 3 Eries in at 100% and found the other 2 at 82 & 87 % . Picked up all the local analogs with nice picture .

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johnpost

· #97 · Jan 5, 2010

loveota said:
My questions to this would be : if i drilled the reflector holes in the mast to the size or slightly smaller than the 1/4" rods used , eliminating the gromets , is there a certain cement that would adhere a steel mast with aluminum rods ? Would the contact of the reflectors and the mast affect the performance of the reflectors ?

having dissimilar metals touch will cause one of the metals to corrode. you could find a nonmetallic tube/pipe that the elements could fit snugly into (and be glued in place) and drill the mast to accept the nonmetallic tube/pipe.

300ohm

· #98 · Jan 5, 2010

Yeah, depending on the rubber, it can deteriorate in a couple of years in the sun. But its not something you should run up the tower and change now. Wait till warmer weather, heh.

The performance of this GH is very good . Slightly weaker than my XG but its now abit closer to the target stations in Erie.

For channels below 30, it should be a bit better than the XG91.

ScaryBob

· #99 · Jan 5, 2010

But its not something you should run up the tower and change now. Wait till warmer weather, heh.

I was going to suggest waiting until the grommets fail. But that's just me.

loveota

· #100 · Jan 6, 2010

Thanks for the reminder John .
The gromets will do for the winter.
I`ve read on this site that running rods through pvc may "electrically lengthen" the reflector rods so that would be out of the question. Next alternative would be rubber tubing. I have all winter to search for the best material. I think i`ll use a short pc of mast and try different materials and options of mounting reflectors to see what weathers the best.
What i did on my buddies attic GH build was use some cable clips i picked up at save&replay . They hold the rods very secure when screwed into a pvc mast . I used 3/4" but next time i`d go with the 1" pvc. I`m skeptical on how this option will hold up outdoors but i`ll add it to the test mast. There was nothing stated about a AV rating on the clips.
The XG was only up to 3% stronger than the GH on ch 35 & below . Nothing to really speak of. Thats what really impressed me with the GH performance along with the wider beam angle. The XG really shines on the top end tho. I`m still recieving a Cleveland station at 114 miles most of the time. And only at 20' up, thats alittle hard to beat.

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