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eHam Forums => DXing => Topic started by: AF5CC on November 06, 2013, 10:53:55 AM



Title: Antenna question: Doublet vs horizontal loop
Post by: AF5CC on November 06, 2013, 10:53:55 AM
OK, here is a question for the antenna gurus and software modelers on the forum.

I currently have a 100 foot long doublet fed with 300ohm twin lead, to a balun, and then with RG-11 coax to the shack. I am getting ready to redo it, but also realize with some extra work, I could convert it into a 200 or so foot horizontal loop. Part of the loop would slope down to a lower height than the rest of it.  It would be in a sort of pentagon shape, and most of it would be 25 feet or so above the ground. 

Would there be any advantage to going to a loop over my current doublet?  I would be using it on 80-10m with a tuner.

John AF5CC


Title: RE: Antenna question: Doublet vs horizontal loop
Post by: NU1O on November 06, 2013, 11:43:49 AM
My first directional antenna was a 2 element Gem Quad at about 20 feet.  I've read a loop antenna is a very quiet antenna and I worked about 270 countries with that Quad in 3 years so I was very happy with it.  I currently have an inverted V fed with 450 ohm ladder line going to a balun and it's so noisy I no longer use it.

73,

Chris  NU1O



Title: RE: Antenna question: Doublet vs horizontal loop
Post by: VK3HJ on November 06, 2013, 05:30:30 PM
I have a large doublet that is 160 metres from end to end and about 22 metres above the ground. It is fed with open wire (2 x #14 spaced 10 cm) all the way into the shack where I use a balanced coupler.
It worked me my first DXCC, and is pretty good 160 m to 20 m.
I have since put up some other antennas and do find the doublet picks up noise. Still, it works extremely well on 30 m, 40 m and 80 m.
Reports from users on air claim the loops are a quieter antenna on receive.
For 20 m and up, you can build a rotary beam relatively easily. Quads are favoured by many. Hex Beams are easy to build and are small, and work well. I've worked over 300 countries with mine in the past three years, so I think that speaks for itself.
Try the loop idea and see how you go. Modeling is limited as there are many variables that are difficult to quantify.
73,
Luke VK3HJ