Clean Up The Shack – Part 3

So, the posts are coming thick and fast at the moment but, this won’t continue as there will be a wait for all the bits to arrive.

Having rifled through screen shots taken some months ago you can see the problem I was having with severe interference. These two powerful signals were generated by an LED security light which was quickly  removed and sent for recycling at the local tip

In my previous post, I stated that I wasn’t interested in the science around Amateur Radio. However without applying a bit of science I will not know if the changes I make are making a difference. OK, so the “opticians” approach – see if it works or not – is a form of a measure but I will see if I can actually put a figure on it.

Unfortunately, I have cocked up a little in that I did not take a screen grab of where I was before I removed a load of power bricks, so, you will have to take my word for it that I had S9 of noise on 40m

After removing the power bricks that has fallen to S7

It is well worth going through every word of GM3SEK’s presentation several times as there is always a possibility that you could miss something. I have now done this and learned something in the process so will be doing a couple more things than originally planned.

GM3SEK said in his presentation – words to the effect of – “you shouldn’t need to filter the DC after you have installed the mains filter”.

However, he clearly demonstrated that switch-mode power supplies can quite easily be a major source of interference. This got me thinking.

My main PSU is a switch-mode and, the PSU for the Loop Antenna tuner is a 24V brick PSU. I am assuming therefore, that there is the potential for these to be causing a problem – no matter how small – despite the hope that they should be excellent quality considering what they were designed for.

I have therefore produced 2 DC filters


The first is about 10 turns of 30A DC cable which comes from the back of the PSU and directly into the Flex 6400


The second is many many turns of the cable from the 24V PSU which feeds the Loop’s tuner.

To my unqualified eye, this PSU does not give me a lot of confidence so I plan to replace it for a decent variable voltage PSU at some point in the future

So, has adding these made a difference?

I would say so!

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