Introduction: Make a High Performance TV Antenna From a Satellite Dish and a Few Parts
I made a high performance TV antenna with a surplus 24 inch satellite dish and some scrap metal and wood.
Step 1: Parts and Tools Needed
1) 24 inch satellite dish and mount (can usually be purchased at surplus electronics stores, ham swap meets or ebay) .
2) Two pieces of scrap wood (1/2 by 4 by 24 inch) The lengths can be cut later.
3) Mini project box. (Radio Shack)
4) Liquid Vinyl Coating of the type to coat tool handles (Home Depot)
5) Gray spray paint (Automotive supply store)
6) RG6 Coax 50 or 100 feet depending on your needs (Radio Shack) I recommend RG6 over RG59 because it has lower losses at UHF frequencies.
7) Sheet copper or sheet steel
8) Aviation shears for cutting sheet metal (Home Depot)
9) Female Chassis mount "F" Connector (Radio Shack or other electronics store)
10) Needle nose pliers, electrical solder, adjustable wrench or socket set, multi-bit screwdriver etc.
11) 10 foot length of galvanized EMT (Electrical Metalic Tubing) 1 inch in diameter. (Home Depot)
12) 3 foot length of ABS black plastic pipe 1 1/4 inch in diameter (Home Depot)
13) Assortment of wood screws.
14) Piece of plumber's metal strapping (Home Depot)
Step 2: Explanation of Technical Details
The actual receiving part of this antenna is called a Bowtie or Butterfly antenna. It is useful for TV because it has a wide bandwidth and has an impedance which is close to the 75 ohm TV coaxial cable impedance. This allows it to be connected directly to the TV. Normally this type of antenna has a flat reflecting element that is placed behind the bowtie. ( I originally experimented by using a flat reflecting element but found the performance inferior to the dish.) This is then placed in the direction of the broadcasting station to be received. I thought that I would try using a variation of this by placing the bowtie in the focal point of a satellite dish with the dish pointed at the signal of interest. I used an online calculator to calculate the dimensions of the bow tie antenna at approximate 600 MHz or American broadcast channel 35 as this was the most distant channel that I wanted to receive. The online calculator can be used here. http://www.changpuak.ch/electronics/Butterfly-Ante...
After assembly and testing, I found that I received 11 channels in my difficult deep fringe area with multiple hills around. I was extremely pleased with the performance of this antenna. Once the antenna is assembled, I will explain some of the adjustments to make as this antenna is extremely sensitive to the direction and elevation adjustments of the dish.
Step 3: Layout of Bowtie Antenna on Wooden Frame With Dimensions
The picture gives the width of the whole assembly as being 15 inches from end to end. The sizes of the wood pieces are not critical but the sizes of the triangles are. For the center frequency of 600 mHz the dimensions of the triangles are 5 inches high by 7 1/4 inches wide. There should be a gap of 1/2 inch between the two pointed ends of the triangles and this is where the two terminals of the RG6 coax are soldered.
Step 4: Mount Plastic Project Box Directly Between Bow Ties.
Before mounting plastic project box, drill a 1 inch hole in bottom directly exposing ends of bow ties. Also drill a 1/4 inch hole in the side of box that is going to face down. This hole will be for mounting the female "F" connector. Make solder connections from center conductor to one side of bow tie and solder the other bowtie to the outside conductor or ground of "F" connector. The project box should be mounted with two wood screws.
Step 5: Once Box Is Mounted; Weatherproof Bow Ties With Liquid Vinyl.
Once connections inside box are made, they should be secured with hot melt glue. The cracks where the plastic box meets the wooden frame should also be sealed with hot melt glue. Once this is all dry the metal should be painted with liquid vinyl. Paint the metal in thin coats letting each coat dry before applying the next. Make sure even the edges of the metal get coated.
Step 6: Put Final Coat of Automotive Spray Paint on Whole Assembly.
I picked this color because I happened to have it around and it matched the color of the satellite dish. I sprayed the whole assembly including the black project box with the cover on. The only part that I covered with masking tape was the "F" connector where it came out of the box. This is where the coaxial cable connector that goes to the TV attaches.
Step 7: Assembly Should Be Mounted on Arm of Satellite Dish.
I mounted the wooden part of assembly to the metal arm of the satellite dish with one screw through the metal arm and four screws through metal strapping. This ensured that the assembly and satellite dish would hold together in foul weather.
Step 8: Attach 3 Foot Length of Plastic Pipe to Satellite Dish
attach a piece of black plastic pipe to back of satellite dish as shown. 1 1/4 inch fit in the mount perfectly. Tighten screws in mount so that it doesn't move. This will later slip over the 1 inch by10 foot length of galvanized EMT (Electrical MetalicTubing). A hole was drilled in the plastic pipe into the EMT and a self-tapping screw was inserted to to keep the satellite dish from moving free of the EMT. More holes and screws can be added if they are needed.
Step 9: Attach Coaxial Cable to Female "F" Connector and Waterproof With Electrical Tape.
The coaxial cable male "F" connector should be hand tightened and then all metal parts should be weatherproofed with a few layers of flexible electrical tape. The lid of the plastic box should also have a couple of layers of electrical tape to cover the seams.
Step 10: Final Mounting and Aiming.
The antenna should be mounted in a place that is away from any obstructions, especially metal ones. It is preferable to keep it away from trees as they will have a definite blocking effect on the signal as these signals are in the lower microwave range. As this antenna is extremely directional, it is recommended that it be aimed in the direction of the weakest station desired. Local stations will come in well without aiming. For extremely distant signals, better reception might be obtained by adjusting the elevation adjustment of the dish. Otherwise just keep the dish at 90 degrees to the horizon. Play with the direction and set the TV to scan. If you have distant stations in a number of directions turn the antenna at 15 degree intervals and scan to see which direction gives you the most stations. This type of antenna is very broadband but you can still optimize it for a certain range of channels by changing the size of the bow tie. As mentioned earlier in the article, this antenna was optimized for 600 megahertz or channel 35.