[300ohm]

I picked up some of these usb devices cheap today:
http://siouxchief.com/Resource_/ProductMedia/63/522 Spec Sheet 10-08.pdf

Heh, usb stands for universal slider bracket.

These would be great for clamping on a CM4221 type mesh reflector onto a round pipe from 1/4" to 1 1/8" OD. Not good for a GH mesh model because of the need for a split screen.

Another thing, the clamps on it are UV resistant plastic. They clamp down on both sides just like electrical wire ties do.

 

[300ohm]

Polyurethane glues like Elmers Glue All Max or Gorilla Glue work great for joining styrofoam and metal. I had been wanting to test this out and just recently did. It holds the piece of coat hanger to the styrofoam panel extremely securely and most importantly, it does not eat its way into the styrofoam.

So if building a GH for attic use on a styrofoam panel, all you would need to do is apply a small drop of the polyurethane glue every six inches or so. The polyurethane glues expand to about 3 - 4 times the size of the original drop as it dries. A slightly damp, but not wet, surface also helps.

 

[300ohm]

It holds the piece of coat hanger to the styrofoam panel extremely securely and most importantly, it does not eat its way into the styrofoam.

Its also great for joining or repairing Styrofoam end to end. I just repaired a custom cut piece I had that the wind broke. If it breaks again, it wont be at the original break point, the joint is that strong.

 

[300ohm]

I did some experiments using Gorilla glue on vinyl siding and plastic outdoor lattice. The result, very poor bonding on those materials. The amazing world of plastics, I guess. Next test with Gorilla glue, grey pvc pipe to white pvc fitting.

 

[300ohm]

Update on black "UV resistant" Walmart nylon wire ties

The black "UV resistant" Walmart nylon wire ties aren't as UV resistant as I had hoped they would be. After 4 years outdoors, they are starting to fall off and are getting brittle on my DBGH gen1 mesh reflector antenna. Of course, that's still 4 times as long lasting as the white nylon wire ties outdoors in my area.

Ill probably use aluminum wire to secure the mesh to the pvc pipe instead of nylon wire ties.

All the 1/2" pvc pipe pieces and even the cheap 96 cent flat black spray paint (thin coat) I used on them and the mesh reflector are in fine condition after 4 years. Just starting to get that right touch of dark greyness in them.

Edit:
Darn it, I just remembered I used black nylon wire ties to secure the fiberglass reinforcing rods on the CM1221. Ill have to redo them too, crap.

 

[coloradotrout]

carbon arrows as reflectors

Anyone know if those carbon hunting arrows can be used as uhf reflectors where aluminum foils is wrapped around them?

They are ridgid, straight (as an arrow ;-) ) and strong.

I used what I think was mostly a fiberglass one, but needed another. The $3 one at WalMart says "carbon composite" or such.

Will the "carbon composite" itself act as a reflector? I'm hoping "no" so that my aluminum foil tape wrap approach will work.

What do others use for this?

 

[coloradotrout]

material for reflectors

What's a good material for the split reflectors -- those that are 12" or so on the left side and 12" or so on the right, with a few inches inbetween?

I am using an arrow shaft (hunting arrow). It's a carbon composite material, but nicely 27" long such that 12.25" on each side with a 2.5" gap is perfect. I wrap around it some aluminum foil tape.

What's are others using?

 

[nikiml]

your method should work

many people use two separate pieces of metal fitted on both sides of a plastic (let say tube)

 

[holl_ands]

FYI: Electrical Properties of Carbon Fibre Materials in fol. U.K. Report:
http://www.dtic.mil/dtic/tr/fulltext/u2/a140261.pdf
Carbon Rods they tested were fairly conductive....but actual "Conductivity" was very poor...much worse than Stainless Steel....but we've also seen claims that Carbon Fibre is "transparent" to Radar frequencies....so it would still be interesting to see a report on how effective it would be as TV antenna elements....

So what is the End-to-End Resistance measurement for a Carbon Fibre Arrow Shaft (please provide dimensions, incl. diameter)??? [VOM or Milliohm capable DVM should do the job....if your meter has it, also try Transconductance function.]

 

[coloradotrout]

PVC frame

I've seen the original frame, but am wondering for a GH2n2 if I should put the main element directly on the frame and then use pvc t-coupler standoffs to mount the 2 uhf relectors, narods, and 2 vhf reflectors?

The frame would be something like this:

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| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
------
with the center verticals spaced to support the interior antenna elements and the outside verticals to support the antenna "tips" and also to support the reflector standoffs.

 

[300ohm]

For indoor use, you could skip the pvc frame altogether and just go with 3 levels of Styrofoam with Styrofoam spacers.

Personally, with a fairly simple design as the GH2n2, I would go with the traditional center pole method. The 2 center sets of uhf reflectors would go into thin tubes (to hold the spacing between them) and then go into a hole in the 1" diameter center pvc post. The 3 vhf-hi back elements would be mounted from tees and pipe in the center post. The front driven element would be mount on 3 sets of tees and pipe from the center post. I would use 1" to 1/2" reducers out from the center post tees to reduce cost and wind resistance. The NAROD to stub separation would be held in place with scrap vinyl siding spacers. The top of the top hat NAROD would be attached to the center pvc post.
I would not glue the pvc joints, but rather use a small #4 screw to hold the fittings in place.
If built this way, using the cheaper grey electrical pvc pipe, it would be durable and wind resistant to use outdoors in the future.

 

[coloradotrout]

Yes, my build is intended to be outdoor-ready, though I may use it indoors for awhile. I'm having difficulty with obstructions to the SSW direction, so getting it on the roof might help.

For the UHF reflectors I have a hunting/target arrow (fiber/graphite) wrapped with aluminum foil. I was planning to just use 2 vhf reflectors.

And yes, I love the snap-on t-fittings. I cut off about 40% on the bandsaw and they work wonderfully.

The single T standoff just seems "wobbly", so that is where I was thinking about supporting both ends of the reflectors.

I was thinking to give 1/2" pvc a try -- thinking the framework will add rigidity. 1/2" is $1.59/10' stick and fittings are $2-$3 for a pack of 10.

 

[300ohm]

The single T standoff just seems "wobbly", so that is where I was thinking about supporting both ends of the reflectors.

I always glue in an old broomstick in the center of the 1 inch pvc mast to add rigidity.