Pete W2PM wrote on the 9th May,
"Andy. Again, it's the laws of physics which apply. The mag loop can only
be sensitive go the magnetic field and less so to the E field only if it is
very very close to noise source. That's just the way Nature works. The sn
improvement is mostly from the very deep and sharp null. You point the null
to the noise. I have seen 20 over S 9 noise go to s1 with cheaply made mag
loops. That's very good. Problem is in an urban and suburban area there
may be many noise noises so eliminating one may not help. But it may. Even
so the mag loop is sensitive to all signals local or distance in a vertical
donut shape. Most DX at 160 and even higher bands comes in at low angles
and most QRN from lightning etc comes in high angle. The only way to get
meaningful and useful performance in a rx antenna is for directivity in the
right vertical and hortizontal fields. This is all for DX performance. If
you have nasty local crud noise coming from a certain area and it creates s9
plus hash in your receiver and all you want to work is domestic, the loop is
fine. And in some conditions its ok DX. I worked my first VK with a mag
loop. But there's no magical properties for it and if you want predictable
DX performance it's fine as a single tool to have but I'd not spend much
money or other resources on it."
Pete, What I have found is that there is still a significant E Field noise
reduction even when the loop is not nulling the noise. This is not just my
observation. There are approx. 5000 ALA1530s in current use in the US,
Europe and Japan. The feedback I have from users experiencing high levels of
local noise is that in most cases the loop affords a noticeable improvement
in the s/n.
Your point in increasing the antenna directivity for Dxing is quite valid if
the local noise is low. Here I use a 2 x K9AYs spaced 40m apart as a 200kHz
to 2MHz phased array; the antennas are run in anti-phase with a varible
delayline phasing controller. Interestingly with this array; if I replace
the K9AYs with 2 large loops I can get up to a 20dB reduction in the local
noise. However, the reduction in array directivity does make this a non
preferred option.
73
Andrew
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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