From: =?iso-8859-1?Q?VIGILANT_Luis_Fern=E1ndez?= <luis@vigilant.es>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Thread-Topic: Small MF ferrite antenna games
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Date: Wed, 27 May 2015 09:22:59 +0000
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Subject: LF: RE: Small MF ferrite antenna games
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Hi Stefan, MF

>Today i've played a bit with a small ferrite antenna for 630m.

Adults never have enought toys ;-)

Vey interesting experiment Stefan. I take your message to call atention to four videos by
Leif Asbrik SM5BSZ. There he shows the complete process of finding the interferences
caused by home appliances in his own house. Understanding the electric and magnetic
field disturbances caused by the offender devices and isolating this noise from the antenna


Viewing and understanding the four videos takes some time but it really worths !
Ramiro, EA4NZ, has got amazing improvements in his hoise floor in Madrid urban enviroment
just using the tips provided by Leif in this videos. He will write an article in his blog
with the basics of this which are really a must for anyone trying Rx on MF/LF in the
noisy enviroment we all suffer actually (IKEA lamps are Chinese after all !)

This are the links to Leif's videos
https://www.youtube.com/watch?v=ItLkn8r4s3E
https://www.youtube.com/watch?v=zsZTX7MQSGQ
https://www.youtube.com/watch?v=kgMbaJDFu9M
https://www.youtube.com/watch?v=C65u7Pmz7a0

73 de Luis
EA5DOM
 

-----Mensaje original-----
De: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] En nombre de DK7FC
Enviado el: miércoles, 27 de mayo de 2015 2:12
Para: rsgb_lf_group@blacksheep.org
Asunto: LF: Small MF ferrite antenna games

MF,

Today i've played a bit with a small ferrite antenna for 630m.
It is 14 cm long and has 8 mm diameter.
Without any calculations i wound a winding of unknown number of turns around the rod and quickly found C about 200 pF at resonance (475 kHz).
Then i added a few turns for a 50 Ohm output (measuring the voltage of an induced signal at resonance. When applying 50 Ohm, the voltage has to decrease to 50%) to the RX.

https://dl.dropboxusercontent.com/u/19882028/MF/small%20MF%20ferrite%20antenna.jpg

As expected the input signal is to low, it does not rise the noise of the RX, so i'm missing about 20 dB. It can't be much more though because i can receive IQ2MI/B clearly in QRSS-30 on 476.180 kHz with 25 dB SNR in 122 mHz, see attachment.
The antenna is hanging in 6m AGL in a tree in my garden...

I'm playing with the idea of a rotary H-field RX antenna for MF, maybe in combination with a stereo receiver and a E-field antenna. Oh and maybe with a colour spectrogram as known from DF6NM. A lot of things to do :-)

73, Stefan

PS: Yesterday, in a CW QSO with DK6SX/p on the loop he once completely disappered into QSO which never happend before when receiving on a omni-directional antenna. So i guess the colour changes in such a spectrogram must be quite interesting and informative...