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In Reply to: RE: diy outdoor fm antenna posted by email@example.com on November 30, 2011 at 18:52:33
2 nos 88cm rods, reflectors?
- These two go behind the dipole driven element
4 nos 68cm rods, directors?
- These four go in front of the dipole driven element
1 no 74cm, diapole.
- This is the driven element
I'm not sure about the spacing. I would start with everything evenly spaced unless you get an educated response from someone else.
Thanks AbeCollins for the prompt responce. Will do this first and wait for input from others on the spacing of the parts.
That's the place to go. He may even have the diagram of your particular antenna!
This year I replicated an older Winegard FM antenna which had 9 elements if you count the horizontaly oriented unique dipole matching of the driven semi-folded element. The spacing went this way:
Distance 1 bewtween reflector 1&2 = 17.46cm
Distance 2 between reflector 2 & rear driven element = 42.07cm (this was a short 70.8cm split element insulated where the 300 ohm antenna leads attached near the boom or baton as you describe it)
Distance 3 between rear driven element & front driven element = 9.525cm (the total length of this element was 160.65cm. The outer ends of the short driven element are connected straight across from their ends to a point perpendicular to this element).
Distance 4 between long driven element and first longest director = 12.38cm
Distance 5 between first director & second director = 32.385cm
Distance 6 between second director & third director = 34.45cm
Distance 7 between third & fourth director = 36.51cm
Distance 8 between fourth & fifth director = 36.83cm
Overall length of the elements from rear most reflector to front most director was 221.62cm. Distances between elements were from center of diameter to center of diameter of the rod elements.
All the reflectors and directors plus the front driven element were grounded to the boom or baton at the point where they met. The only exception was the short driven element which was split at its center and cut about 2.5 cm from the boom outer dimension and attached with a plastic insulator.
If you compare these spacings to some of the ones you see on Brian Beezley's site I think you will be very close to usable spacings for your antenna.
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