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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.
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...
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
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