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How to make antenna?

dl09

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I know this is probably a dumb question. but i have been studying radio technology.
if i use a aluminum strip that is 1/4 of a wavelength long as an antenna, will it have
an impedance of 36.5 ohms if above a groundplane that is large compared to the wavelength?
Copper wire cost money and aluminum would be far easier to obtain. I live below the poverty line, please answer the question.
 

BradtheRad

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In college we used anything made of metal for an antenna. Including ordinary steel coat hangers, Three feet long only has 4 ohms of DC resistance.

Reactive impedance is not the same as resistance. Reactive impedance comes from rf interaction with the antenna size and shape.
--- Updated ---

I recall the dipole antenna was popular. Easy to make from 300 ohm twin lead. That was antenna cable in the old days. I don't recall hearing anything about needing a ground plane to bring in FM band.
 

danadakk

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This might help -



Regards, Dana.
 

dl09

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This might help -



Regards, Dana.
I don't think this told me if an aluminum strip 1/4 of a wavelength above a groundplane that is large compared to the wavelength, has an impedance of 36.5 ohms, so does it have an impedance of 36.5 ohms?
 

volker@muehlhaus

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If you read the article that I linked, you can see a picture what it must look like.
Direction of the wire matters, it must be vertical away from the ground plane.
Material is not critical
 

EdwardJohn

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In the matter of a few hours, you can provide yourself with access to hundreds of digital channels. Follow the steps listed below and have your own, homemade digital TV antenna in no time.

Materials:


  • 21 ½-by-2 ½-inch wooden board
  • 18 washers
  • 20 screws
  • 15 feet (457.2 centimetres) of wire
  • Reflector Grid
  • Balun
Tools:

Here's what to do.

  1. Mark the wooden board You will be making four sets of two holes, as follows: two holes 2 inches (5 centimetres) in from the edge of the board, and two more holes every 5 1/4 inches (13 centimetres) along with the board [source: Current]. Using a measuring tape and pencil, mark your 21 ½-by-2 ½-inch wooden board where you will drill holes.
  2. Drill the holes Drill holes into the board using the pencil marks as your guide.
  3. Cut the wire Using wire cutters, cut eight 17-inch (43.18-centimetres) pieces of wire. Bend the wires into "V's" with 7-inch (17.78- centimetre) sides and a 3-inch (7.62-centimetre) gap between the two legs of the "V."
  4. Attach the wires to the board Attach the wire "V's" to the board with screws and washers, using a screwdriver.
  5. Zigzag the wire to attach the connections Using more wire, connect the "V's." Coil the wire around the screws moving in a zigzag pattern across and down the board. Make sure the wires don't touch where they cross one another.
  6. Attach the reflectors Secure the reflector grid to the back of the board using screws and washers.
  7. Attach the Balun The Balun has two wires with screw holes. Feed a screw through the holes. Secure the Balun to the zigzagged wire by screwing it into place. Make sure the wires don't touch where they cross one another
 

betwixt

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Post #5 describes a poor quality Yagi antenna for a specific frequency (not specified) and with no impedance quoted, no specification for the balun and no specification for the feeder. It will probably work for something but please do not assume it will work for your particular needs.

Perhaps EdwardJohn, you can explain the difference between this digital antenna and an analog one. Also can you name one of the "hundreds of digital channels" it will let me access.

Brian.
 

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