QRM busting

Mads LA1TPA recently visited Julian G4ILO’s shack and was so impressed by his approach to cutting through the QRM using an MFJ-1026 Noise canceler and a pa0rdt-Mini-Whip active broadband RX antenna, he’s replicating the solution at his own QTH.

His post links to info on both the MFJ-1026 and the pa0rdt Mini-Whip.

MFJ-1026 noise canceler
MFJ-1026 noise canceler

Julian G4ILO’s site has an extensive description of the MFJ-1026 explaining that it’s a noise canceler, not a noise blanker or a noise reducer – as well as a ‘look under the bonnet’. It’s most effective when the noise is coming from a single point source, not multiple sources. So the canceler can reduce noise from a neighbour’s switch mode power supply, TV or computer it may be less successful dealing with general powerline noise.

For Julian’s station it did the trick and as he concludes,

“The MFJ-1026 is expensive for what it contains and quite poorly made, so I don’t feel any pride of ownership of it. It’s also a hassle having to tweak its controls whenever I change bands. But pressing the button to take it out of circuit quickly reminds me just why I have it.

I’d probably had sold my equipment and quit the hobby if it wasn’t for the MFJ-1026.”

You can also preview the MFJ-1026 manual here.

pa0rdt mini whip antenna
pa0rdt mini whip antenna

The English-Dutch-Italian pdf about the pa0rdt Mini Whip explains,

“After several fruitless attempts to make an active loop work in a city environment, it was found that the electric field from local noise sources was contained within the house. The magnetic field of local noise sources was not contained inside the house, making weak signal reception at LF impossible.

Hence an electric field antenna was called for. Tests were performed using an active whip antenna, designed by G4COL. Results were encouraging and the whip length could be reduced from 100 cm to 30 cm without loss of performance. It became clear that at LF an active whip is a capacitance coupled to the electric field.

If it is accepted that a whip is a capacitance coupled to the electric field, shape becomes irrelevant, as long as the required capacitance is available. In practice the “whip” can be e.g. a small piece of copper clad printed circuit board.”