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Re: LF: AW: RE: active ant on metallic mast

To: [email protected]
Subject: Re: LF: AW: RE: active ant on metallic mast
From: "Roelof Bakker" <[email protected]>
Date: Sun, 07 Feb 2010 10:39:09 -0000
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Hello Stefan,

A receiving loop will give the best signal i assume, but it is not very easy to handle if one is always /p.

There is floating a lot of untested lore around, regarding reception antennas. When I started listening at LF 8 years ago, I was convinced that loops were the way to go. I spent a whole winter season to get them to work, but failed due to local noise pick up. I decided that it was impossible to get proper results in a city location and almost gave up. As a last resort and just for the fun of it, I build an active whip and much to my surprise it worked.

At the time I have made a lot of tests comparing active whips and loops on a field location. They were aligned for the same output on a local NDB on 399.5 kHz. The results were that I could not find any difference between the loop and the whip, except the directive properties of the loop. The poor results of the loop at home were due to the fact that the house acts as a faraday cage for the electric field. So local noise in the electric field is attenuated, whilst local noise in the magnetic field is not.
At 400 kHz the attenuation was 30 dB.

In a rf-quiet location both antenna types perform equally well.

The whip has been used almost 7 years now as an ongoing experiment with rather unexpected results. I have received with aural copy the now closed down NDB on Easter Island in the Pacific. But I am convinced that a loop at a good location should have given similar results.

And yes, a whip is much easier to handle when going portible; especially when it is housed in a piece of plastic pipe measuring 30 x 60 mm.

73,
Roelof, pa0rdt





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