Re: LF: Re: VLF in Spain

[Daniele Tincani <danieletincani@yahoo.com>]

Hi Stefan, VLF,

 

yesterday evening I sent a message on this topic which probably was discarded because of > 200KB attachments. Anyway, I walked through old files on my hard disk looking for results of my tests with an active loop antenna and a couple of active whips. I can confirm that both the H-field antenna and the E-field ones performed more or less the same, because of the fact that performances were limited by my very noisy environment rather than by antenna characteristics. With either type of antenna there were no chances to receive Stefan's transmission in the 5KHz and 6KHz ranges, while it was possible to consistently receive the 8970Hz signal. In that case, the active loop showed some marginal advantages, probably because of its directional radiation pattern and nulling capabilities. However I have to remark that during my tests the E-field antennas were installed on my balcony at 5th floor (the same as the loop antenna), close to domestic noise sources, with no attempts to put them e.g. a few meters in the high by means of a fishing rod or other support, which probably would have produced significant improvements.

In fact, it is common opinion that E-probes perform very well if you can install them at least say 5 meters away from your house perimeter or high above the roof (and far from other noise sources of course). This is because in the near field they react mainly to the E component of noise, which is attenuated significantly by walls, distance, etc.. In case your are forced to stay close to your domestic environment or have other nearby noise sources like high-voltage powerlines, etc., may be a properly built loop antenna could offer some advantages because of its eigth-shaped radiation pattern and nulling capabilities.

I add a wideband capture of the spectrum at my location to show you how it looks usually. It was captured using an E-probe that I built based on Stefan's design.

Best regards

Daniele

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From: Stefan Schäfer <schaefer@iup.uni-heidelberg.de>
To: rsgb_lf_group@blacksheep.org
Sent: Thu, June 16, 2011 2:51:37 AM
Subject: Re: LF: Re: VLF in Spain

Hello Alberto and Daniele and VLF,

Yes, this is what Chris/4X1RF observed as well. It can make a very significant difference just to lift the antenna by 2m higher above the previous location!

73, Stefan/DK7FC

Am 15.06.2011 16:50, schrieb Alberto di Bene:

On 6/15/2011 3:54 PM, Daniele Tincani wrote:

Additionally, I didn't perform specific tests with the E-probes, like for example attaching them to a fishing rod (or other support)
to put them well outside of my balcony at 5th floor, that probably would have given a substantial improvement.

I can confirm from my direct experience that an E-probe must be placed up in the air, free from obstacles.
When I built for the first time the Roelof's mini-whip I tested it on the balcony of my house, on the second
floor of a two-story single house. It performed so badly that I thought to have wasted my time and my money.

Then, remembering a few suggestions read on Internet, I moved it to the highest point of the highest chimney
of the house, far from obstacles, with a free 360 degrees range, on top of a 2-meter pole.

It resurrected to a new life ! This is how the Russian Alpha stations are received from my mini-whip on the roof :



So my suggestion is to place an E-probe antenna as high as possible, free from nearby obstacles.

73  Alberto  I2PHD

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