is this antenna sutable for dijatle?
----- Original Message -----
From: Max Robinson
To: [email protected]
Sent: Thursday, July 23, 2009 1:00 AM
Subject: Re: [BlindHandyMan] Re: Build a T.V. antenna.
I think it's a variation on a UHF bowtie with reflector. Although the
crossed over feeders remind me of a log periodic.
Regards.
Max. K 4 O D S.
Email: [email protected]
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----- Original Message -----
From: "Tom Fowle" <[email protected]>
To: "blindHandyMan" <[email protected]>
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]
>
>
>
>
>
>
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