[Antennaware] K9AY Terminated RxLoop wire length

K9AY k9ay at k9ay.com
Tue Oct 14 09:59:38 EDT 2008


The signal capture (voltage or current) of a small loop is proportional to 
the area. Thus, double area is 6 dB. My larger loops had almost 1.25x the 
area of the "original" loop, so I expected nearly 2 dB more signal.

With my larger loops, the wires were simply extended horizontally, making 
the loop wider, but not higher. The exact shape of the loop is not critical, 
although it affects the vertical angle of the null. Wider loops have lower 
null angle, taller loops raise the angle of the null. However, at the 
extremes of either shape, the area enclosed by the loop is smaller for the 
same length of wire; a diamond or square shape is more efficient (circle 
would be best!)

73, Gary

> Hi Gary
> Very interresting, 2 dB is not bad for just 2x2 meter (+15%).
> When You added wire, did you strictly maintained the upper to lower wire 
> ratio (8:5), in order to maintain the shape ?  that would elevate the 
> right/left slightly from ground, or did you maintain the 1.5 meter "above 
> ground" at the right/left side of the shape as the original design 
> specifies ?
> --
> OZ1AXG Flam
>> Flam,
>> In 2007, I experimented with larger loops -- same height as the original
>> (about 8 meters), but almost 2 meters more on each side. In theory, the
>> signal increase should have been 2 dB, which is hard to measure, but I am
>> certain that these loops were more sensitive. The improvement was easy to
>> hear in the AM broadcast band.
>> Modeling shows that the F/B will be a little less on 80M, but there are
>> other variables such as ground that also affect this, so it may remain
>> useful.
>> It is easy to try the larger loops since you are not changing the height. 
>> Go
>> ahead and see how much it can help!
>> 73, Gary
>> K9AY
>>> Hi
>>> I put together a Terminated half loop, and it is working very well. Its 
>>> a
>>> simple construction with only one loop (east/west) and a home made 
>>> control
>>> box (no pre-amp, but working on putting one together). Especially the 
>>> F/B
>>> is
>>> very impressive!
>>> Receive signal level is good on 80 meters. However on 160 meter the 
>>> signal
>>> is very low.
>>> Dimentions of the antenna is 7.80 meters highest point; 0.40 meter 
>>> lowest
>>> point. Sides are 8 meter (upper) plus 5 meter (lowerl) = total 26 meter.
>>> I have read on the internet, several people adding wire to increase 
>>> signal
>>> levels on 160 meter. Adding wire to the current construction can only be
>>> done by making the antenna wider.
>>> Question: If I where to add 3 meter to each side of the antenna, i.e.10
>>> meter (upper) puls 6 meter (lower) side, getting a total length of wire 
>>> of
>>> 32 meters how would this effect the vertical and horisontal radiation
>>> patterns ? (Im a aware that this would compromise 80 meter opertation 
>>> with
>>> a
>>> looplength > 0.3wl)
>>> Sincerly
>>> OZ1AXG Flam

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