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.
Check out ON4UN Low Band DX book. Especially on receive antenna RDF.
Sent from my iPad
On May 9, 2011, at 16:31, "Andy Ikin" <andrew.ikin@btopenworld.com> wrote:
> Pete W2PM wrote on the 9th May,
>
> "I notice they repeat the incorrect assertion that these magnetic loops work
> by being sensitive to the "magnetic field" rather than the electric field and
> that has been long shown to be false - these antennas are not sensitive to
> the magnetic field at all but very close proximity to the sources."
>
> Pete,
>
> If what you say above is true; then how does one explain that I can achieve
> up to a 30dB reduction in local noise pick-up with a Wellbrook ALA1530 loop
> antenna compared to a Datong AD370 Active Dipole ( E -Field ) when the two
> antennas are a few metres away from 11kV powerlines. Both active antennas
> have a similar Antenna Factor to signals in the far field. Also if I use a
> Mobius loop with a similar gain as the ALA1530, I get the same noise
> reduction. Note: both loops were positioned not to null the noise.
>
> If the loops were sensitive to the electic field then there would little
> difference in the noise reduction campared to the Active Dipole!
>
> 73
>
> Andrew G8LUG
>
>
>
>
>
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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