Hey Tom,
Are the plans and such on the web and if so can you give us a link. Some of us
partials might make use of those.
Ron
----- Original Message -----
From: Tom Fowle
To: blindHandyMan
Cc: [email protected]
Sent: Wednesday, July 22, 2009 5:15 PM
Subject: [BlindHandyMan] Re: Build a T.V. antenna.
Here it is folks, hope it makes sense.
BTW, the plans schematics and all are free under the good old "GPL" public
license.
Complaints about my discription welcomed, complaints about the resulting
device
are not my job! <GRIN>
http://www.digitalhome.ca/ota/superantenna/
Text description how to build the Gray-Hubberman U.H.F. T.V. antenna
Tom Fowle
Smith-Kettlewell Rehab Engineering Center
San Francisco
This antenna will seem strange to anybody with experience in "normal"
looking
TV. antennas, it looks like it'd be seeing the sky but it seems to work.
Materials:
1 piece of wood; 1 by 3 or 1 by 4, 22 inches long.
about 25 feet of No. 14 bare copper wire.
8 No. 8 by 3/4 inch wood screws, round or pan head.
8 No. 4 by 1/2 inch wood screws round or pan head.
8 flat or fender washers for the No. 8 screws, mine are 3/4 inch diameter
but that's maybe a bit large.
2 each metal screens 9 by 15 inches. I bought 4 vent screens measuring
about 4 by 15 which had lighter frames and were cheaper than
the 9 by 15 inch units.
1 each 75 or 300 ohm "Balun" or matching transformer, used to connect 300
ohm T.V. twin lead to 75 ohm cable. Available at Radio shlock
or anywhere that sells T.V. accessories.
Tools:
ruler:
drill with bits for pilot holes for the screws;
wire cutters;
screw drivers;
"vise for holding the wood while measuring and drilling.
The antenna consists of 4 pairs of V shaped elements whose points are
mounted in pairs across from each other on one surface of the
board. The V's have 7 inch legs and have 3 inch spread at the
open ends. There points are mounted under screws and washers
along the board in pairs with a separation of 1 inch across the
board and 5-1/4 inches between pairs. These pairs of V's are
connected together by "feeder" wires as detailed below.
The two screens, called reflectors, are mounted on the opposite
surface of the board centered between each pair of 2 V's.
With the board long way pointing away from you,
Starting from the close end of the board, measure up 2 inches for the first
pair of screws for the V's. If you're using a 1 by 4, which is
actually 3 and a half inches across, measure in from each edge
of the board 1-1/4 inches. Thus your first holes are an inch
apart and 2 inches up from the end of the board.
Drill pilot holes for the No. 8 screws. Measure up from these holes 5-1/4
inches and locate the second pair of pilot holes also an inch apart centered
on the middle of the board's crosswise dimension.
Again go up from the second holes 5-1/4 inches for the third pair
and similarly again up 5-1/4 inches for the 4Th pair. This
should leave about an inch free at the "top" of the board.
Now turn the board over. Starting from the bottom, measure up the center
line of the board 4-1/2 inches. Mark this point.
This mark is in the center of the long rectangle made by the
lower 2 pairs of No. 8 screws but on the opposite surface of the board.
find the center of the similar rectangle made by the upper 2 pairs of holes,
not the middle of the entire antenna. Put another mark there.
These marks are to be the centers of the two reflector screens. The 9 by 15
inch screens are mounted across the board centered below each 2 pairs of No.
8 screws. Since I have 2 scrreens each measuring 4-1/2 by 15,, I screwed
the centers of each long edge of 2 screens to the marks I've mentioned. I
then aligned the screens to be at 90 degrees from the long axis of the board
and installed No. 4 screws in the remaining long edges of of each screen.
Now turn the board back over with the No. 8 screws up and install
No. 8 screws with flat washers in each hole. Do not tighten down
all the way, leave room for wires under the washers.
Cut 8 14 inch lengths of wire. Bend each into A "V" with 7 inch
legs and 3 inches between the open ends of the V's
Fasten each V under one of the No. 8 screws and washers with the open ends
of the V's pointing out away from the center of the board.
Now cut 2 lengths of wire about 22 inches long. These connect the pairs of
V's as follows.
With the antenna in front of you long wise pointing away from you, start the
first feeder wire at the bottom left V's screw. It goes up and across to the V
that's second up on the right. This first feeder wire then goes straight up
to the third right hand V. Then it goes across to the top left V.
The second feeder wire starts at bottom right, goes up and across to the
second up left, then straight up to the third left and up and across to the
top right V's screw.
Make sure the feeder wire's don't touch where they cross, I had no trouble
just bending them apart, but some tape between wires here wouldn't hurt.
Now you can tighten down the No. 8 screws that hold the V's and feeders.
Check that the V's still have 3 inch open ends and that they all
point symmetrically outwards.
Find the middle of each feeder wire.and install a No. 4 screw exactly
adjacent to it. These screws also take the open "lugs" from your matching
Balun or transformer.
Connect your chunk of 75 ohm cable to the transformer and route it straight
down the antenna's center and off the close end.
If I were going to use this out doors, I'd give it a spray of
paint the screws will probably rust pretty fast.
Remember the antenna is to be mounted standing up on it's end. The most
effective direction is from the reflectors towards the V's.
Hook it to your.V. and move it about and turn it till you get best
reception.
Your sightlings will love you.
Tom Fowle
Embedded Systems Developer/ Rehab engineer
Rehabilitation Engineering Research Center
The Smith-Kettlewell Eye Research Institute
2318 Fillmore St.
San Francisco, CA 94115
415-345-2123 (Voice)
[email protected]
[Non-text portions of this message have been removed]
