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Re: LF: Re: MiniWhip antenna, fiber optic /p tests

To: [email protected]
Subject: Re: LF: Re: MiniWhip antenna, fiber optic /p tests
From: Stefan Schäfer <[email protected]>
Date: Sun, 14 Jul 2013 18:37:37 +0200
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MF,

I just came back from a field experiment, using the short active dipole which is resonated to 475 kHz (4.7 mH and 10 mH fixed inductors in parallel plus a few pF (<10) for fine adjustment), with fiber optic cable.

Tests were done in JN49HK94RW, a distance of 2.3 km, see http://no.nonsense.ee/qthmap/?qth=JN49HK94RW&from=JN49IK00WD Since it was 17 AM local time i assume there was no skywave component. The location is an open field without trees or houses in a radius of at least 30m and without electricity in a radius of at least 100m.

Some results were interesting for me. However i have to do the test again because my own signal was so strong that some measurements overloaded the soundcard. I have to reduce the power by 30 dB or so in the next test, or i have to choose another location.

The signal levels were shown in my battery powered netbook using SpecLab Software. Noise measurements were done in 1 Hz NBW.

I do not have a high and stable plastic pole so it was just possible to do the test in 1.75 m above the ground. Tests were done in a horizontal and vertical position of the dipole. For the horizontal test i tried both, poiting of the dipole to the TX location and 90 deg rotated to it. There was no difference. The tests were done with a floating and a grounded dipole (grounded to a local earth rod, just 10cm into the soil).

Images:
https://dl.dropboxusercontent.com/u/19882028/MF/20130714_165114.jpg (Receiver) https://dl.dropboxusercontent.com/u/19882028/MF/20130714_170616.jpg (Vertical) https://dl.dropboxusercontent.com/u/19882028/MF/20130714_165421.jpg (Horizontal)

Results are attached in the image.

Now we can discuss about the results, or not :-)
As i said, i have to repeat the test because a few of the measurements were to close to the soundcards ADC limit and caused nonlinearity...

73, Stefan/DK7FC

Attachment: MFtest2.png
Description: PNG image

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