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Re: [IRCA] Some help with "large" loops?
Nobody's jumped in yet Brian, so some quick opinions.
- How important is the shape and symmetry of the loop; e.g. wire sag,
sloping ground, differing heights of the two vertical components?
You can get away with some variation (I know I've discovered after
the fact that one vertical leg wasn't as tall as I thought it was)
and sag, but it doesn't hurt to aim for symmetry.
- How important is the height above ground for the bottom wire?
I have a Flag that is about 10 feet above the ground for the bottom
wire, and found not a lot of difference from one that is a foot or so
above the ground, at least so far as nulls are concerned. The higher
antenna may be a bit quieter when dealing with local noise.
- Does the type of wire matter much (within reason)?
not that I'm aware of
- If I want something reasonably sturdy and with the possibility of going
up to 20-25' height, am I looking at $100 or more for a suitable pair of
telescopic fiberglass poles? I don't plan on deploying this if it's windy.
I wouldn't go for height to start with, so keep it simple. A
properly tensioned 1x2 x 10 or 12 feet can be sturdier than a
telescoping pole. Poles are great for portability or instant antennas however.
An amplifier can help if you think it's a bit deaf. I really like
the Wellbrook FLG100, but it's pricey.
It sounds like your antenna has to be close to the house by
necessity, so you might be losing some of the characteristics (and
getting additional noise). If you think that might be an issue, you
could look into Mark Connelly's Micro Super
Loop: http://www.qsl.net/wa1ion/loop/car_roof_loop.htm I don't
think it has to be attached to a car, hi. (amplifier necessary)
A remotely adjustable termination can help at least when you are
getting a feel for the antenna. Again, Mark Connelly has
suggestions. I still have mine remotely adjustable, as sometimes
that extra couple of dB less on the splash can bring out the DX.
best wishes,
Nick
At 07:25 18-11-14, you wrote:
I'm hoping to pick the brains of those of you who have experimented with
various "modern" loop designs. With limited room, poor ground
conductivity, and not being able to set up something permanent, I've been a
bit discouraged by the sizes of antennas that people are using to get
nulling patterns other than a figure-eight. However, after looking at
Bruce Conti's page on the "Super Loop" (corner-terminated, corner-fed), I
realized that this was something I could try after all.
This weekend, I threw together a "portable" 8' x 25' loop using PVC pipe
and wood for the two end supports. I still need to do the termination and
impedance matching right, but my "close enough" beta version was promising
as far as signal strength across the BCB and noise levels, although the
quality of the backside nulling wasn't as clear (the whole point of this
experiment is to null out SoCal and/or northern Baja California). This was
squeezed in between the house and carport, the only practical corridor I
have for something this size. I would like the ability to have a support
20-25' high, mainly to get the loop more clear of structures.
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