n1zuk
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join:2001-10-24
South Burlington, VT
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| reply to jacour
Re: Delta Beams
Good subject. I had great success with a 2 element Delta on 6M. A 2-el Delta has about the same gain as a 3-el Yagi, with a very similar radiation pattern.
I feel that there are several reasons that Delta (and for the same reasons, Quad) beam antenna aren't favored over Yagis:
-- Mechanically, more of a bear to set up and maintain. Several spreaders for each element, then the wire element itself.
-- Wind loading. Even though the boom is shorter (and one less element for the gain) you do get a lot of surface area to catch the wind.
-- Impedance matching. Not the easiest setup to get a good match. Most everybody knows and understands the classic yagi Gamma Match.
For my 2-el 6M, I avoided most of it by fixing it facing SW (being in Vermont, where most e skip comes from), and building a very simple antenna. A 1x1 strip of lumber with two holes on the end to hang from some trees, and two more holes appropriately spaced for the elements. Cut wire for the driven and reflector. some 75ohm coax for a tuning stub. I used string to hold out the other corners, tied to other low branches and stuff. Ugly, but worked for over 300+ contacts, including VP6BR on 6M. Even though it was retired for a 5-el yagi that I could rotate, I still have that antenna. 
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GeekGirl1
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join:2007-01-28
Morrisville, PA
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| I used to have a 2-el tri-band HF quad antenna. Fiberglass supports. Carried it up to the top of my 50' Rohn-25 tower over my shoulder (really!).
Then the wind hit it. Wind loading is an understatement.
One thing that you realize after a while is that the wire is stressed at the points it passes through the supports, i.e. the apex where it forms the "squares". Over time, the wire breaks. That will happen. A pain to fix. Hence, the popularity of rigid metal elements (yagi).
If you remember all those CB quad antennas from a long time ago- just about every one had broken wires on it. Not many were kept in good condition. |
