My Grey-Hoverman Antenna

SBGH-6

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SBGH-6
NARODs for VHF
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I chose the SBGH-6 for both the ease of construction and the option of adding NARODs for VHF reception, which I need as I have 3 stations in NY on VHF-hi. (Ch's 7, 11 & 13) Plus I think it's a rather unobtrusive design - handsome even, as antennas go.

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For the full story of the Grey-Hoverman antenna click here

Design Dimensions
SBGH-6_dim.jpg

I first have to admit I'm pretty much the definition of a pack-rat ;-)
So I had much of what I needed for this project lying around somewhere.

Here are the construction details...
(For a UHF only antenna, the NARODs have yet to be added.)

Background & basics...

I used #8-AWG copper wire for the driven elements (actually recycled from the trial version) and 1/2" copper pipe (~$7.29 I think for 10' at HD or Lowes) for the collinear reflector rods. 1/2" sch 40 PVC was used for the spline, along with 1/2" CPVC for the reflector rod spacers and the posts of the element supports. I cut up 1/4" thk Lucite (actually measured .220" thk.) for the element support plates and 3/32" thk Lucite for the NAROD supports on my table saw. Once drilled these will also help me align the NAROD reflector rods. But these details will follow on another page...

The inside diameter of 1/2" sch 40 PVC is just shy of 5/8" and the outside dia of both 1/2" CPVC & 1/2" copper pipe is .625" so a very nice fit was attained by "reaming" the sch 40 with a 5/8" spade bit. This was done in a hand drill at very low speed. Just as an aside, I tried using the grey elec conduit first but didn't like it, as it was too soft and didn't ream well. The white plumbing pipe is harder and shaves nicely for this process. I also figured the stiffer the better. All sch 40 was reamed before assy where it had to accept either 1/2" CPVC or copper pipe.

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Fig 1

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Fig 2

To get accurate cuts when cutting the PVC I first used a std pipe cutter to start the cut. [fig 1] Be careful to use even pressure and not to cock the piece as it will spiral on you. Then I finished off with a ratchet PVC pipe cutter. [fig 2] A fine tooth saw in a miter box would also get good results.

Fig 3 shows the spline assy laid out. Both the reg & cross tees I got from HD & Lowes measured 2-1/2" overall, with a 3/4" inset for the pipe - which worked out perfect for the close dim's, where the tees butt, only needing 1-1/2" joiner pieces. 4" pieces are req'd at the rest of the locations. Be sure to immediately wipe away the excess glue that will form a "fillet" where the tees have to butt each other, or you won't end up with the right dimensions.

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Fig 3

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Fig 4

To maintain squareness of the spline assy I clamped a speed square to the table and held the element support tees against it while gluing with PVC solvent weld. [fig 4]

2-1/2" pieces of PVC were glued into the 4 middle cross tees for the reflector rods. The rods themselves were cut to length with the pipe cutter. 1/2" CPVC cut & sanded to .787" (20mm) are the spacers inserted between the reflector rods. I should note that the pipe seemed to tighten up a bit after it was glued in place - my removable keyless chuck from my 18v Firestorm drill came in handy to do a final quick ream by hand with the 5/8" spade to get a good fit on the 1/2" copper reflectors

Fig 5 shows the rearward facing support tees for the NAROD reflector rods, the only pieces not glued. I did glue 3/4" pieces of pipe in one side of each tee, and the 1-1/2" "nubs" of pipe are glued into the spline tees. These will be held together with brass screws locking the copper rods from the backside of the antenna. (This is also how the rest of the reflector rods themselves are held in place, once inserted into the PVC.) If you're building a UHF only version then the NARODs are not required, and you can replace these tees with 2-1/2" lg pieces of pipe also.

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Fig 5

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Fig 6

The element supports...

I glued 1-1/2" lg pieces of 1/2" sch 40 PVC into the forward facing element support tees, then drilled & tapped for #10-32 nylon bolts to hold the 1/2" CPVC element support posts. [fig's 6,7 & 8] (Yes, I had nylon bolts lying around ;-) And my removable keyless chuck once again came in handy when I couldn't find my tap handle!)

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Fig 7

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Fig 8

For the element support plates I cut 1/4" Lucite into 1"x6" strips and laid out the mounting holes with a caliper for accuracy. Upon the advice of one of the resident experts on the DHC forum (300ohm) I chose 89mm (3-1/2") as a feedgap dimension as this is known to increase gain over the previous 44mm gap. I center punched & drilled all three holes, then counter-bored the center hole 1/16" deep with the 5/8" spade bit to accept the CPVC standoff post. [fig 9] I then tapped the element mtg holes 10-32. (I also ran the tap thru the center hole just to get a little thread so I could seal the hole against moisture intrusion with a nylon bolt.)

I cleaned all parts with acetone and glued with super glue. I did do a test to see if the PVC solvent weld would attack the Lucite and while it did somewhat, the super glue appeared to attack both materials better & seemed stronger. Fig 10 shows the completed post assy's.

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Fig 9

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Fig 10

I put washers on the nylon bolts to mimic the element wire & lock washers and cut off the excess screw. [fig 11] I then assembled the element supports into the tees and set the height. [fig12] Once everything is working a bead of solvent weld glue applied with a Q-tip where the CPVC meets the PVC will make it more permanent if desired.

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Fig 11

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Fig 12

Straightening & securing the elements...

For the driven elements I straightened the #8 wire using the drill-n-vise method: Lock one end in the bench vise and put the other in a cordless drill and spin. This not only straightens the wire, but also work-hardens it, making it much easier to make nice tight bends. (Better, smoother results are achieved spinning in only one direction; spinning back & forth seems to create "ripples" in the wire.)

I measured off the bend points and marked with a sharpie, drilled a piece of scrap wood & put a 10 penny nail thru and made the bends.

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Fig 13

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Fig 14

I wanted to make sure the elements wouldn't turn out from under the screws so I silver soldered #10 brass flat washers onto the element wires at the hold down points with a propane torch. I made a quick jig from a piece of asbestos shingle I had lying around. I drilled & tapped a 10-32 hole and put a stainless screw in it, then positioned the wire over the washer with a little weight on top. [fig's 13, 14 & 15] In retrospect I would just drill a press-fit hole for a #10 nail in the shingle 'cause the solder filled in the threads of the screw, causing me to have to unscrew the jig from the washer/element after soldering. It also needed to be drilled out afterwards - easily done by hand with my trusty removable chuck.

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Fig 16

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Fig 15

Then I mounted the elements using double flat washers at the balun connection, and lock washers under all the screw heads. [fig 16] I chose to use brass screws at only the balun feed points for a secure connection, as I was trying to maintain a "no metal" rule throughout the rest of the antenna to avoid the possibility of any extraneous interference.

Once finalized I removed the driven elements & masked the reflector rods, and all plastics were painted. Then the ends of the copper reflectors were capped with plastic caps to keep water out - which I of course have lying around... 1/2" CPVC end caps could be substituted here.

I'd also like to get an accurate weight on it as it is a bit on the heavy side, I estimate it at around 7 Lbs. Due to the weight, and the stem mounted design, I plan to reinforce the 2-1/2' - 3' stem, which will be glued into the bottom cross tee. I plan on reaming the 1/2" sch 40 with my spade bit & extensions and putting ~6" of CPVC at the top and filling the rest with the remaining copper pipe. Hopefully that should give it some extra rigidity.

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Here are some photos of the assembled antenna before and after paint.

If all you need is UHF, then this is ready to go.

For me, I still have to add the NARODs for VHF reception. The details can be found on next page...

On to the NARODS...

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Hope this was of help to someone!

Hooper

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The Gray-Hoverman antenna designs, schematics, and diagrams on this site are Copyright 2008 and are free: you can redistribute them and/or modify them under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at our option) any later version.

These designs, schematics, and diagrams are distributed in the hope that they will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

For your complete copy of the GNU General Public License to go along with the designs, schematics, and diagrams, see:

http://www.gnu.org/licenses/gpl.txt

Thanks for dropping by and having a look at my work.
Please let me know what you think - any comments or suggestions are appreciated!

  

Click here to email me directly if you have something you'd like to discuss.

All done just for fun,

And to see if I can produce something that performs...

And if I can ditch Dish Network in the process, all the better! :-)