April 2017 - Aerial Phasing Noise Canceller

A few months ago on the GQRP reflector we discussed these devices. How they work and how effective they could be.

I am fortunate not to have a big local electrical noise problem. Nick G8INE (who I often build stuff with) does have such problems. So he ordered two prototype printed circuit boards and sent me one. He managed to completed his unit first and the result was very impressive. The club member doing the development is Terry VK5TM who is now able to offer printed circuit boards and shortly, he hopes even a kit. This will be supplimented by an article in a future Sprat.

My unit produced positive results, but I learned that I probably wasn't the best candidate for one given my better environment.

In the photo below you can see how I build stuff "Alfresco style".

Long ago I discovered that the way to guarantee that a project will not work is to put it straight into a box and only then test it. That is just mocking the radio gods and without doubt they will smite you. I used to find that most of my projects didn't work first time and then I had to remove the circuit boards to start debugging.

So I now always build on a small plank of wood and transfer to a case only when the project actually functions correctly.

On the left, there is a pot to control antenna gain into the unit. The middle pot controls the gain from the smaller sense antenna. The rightmost pot controls the phase of the sense antenna signal.

G8INE Noice CancellerFirstly, a link to a convincing video showing Nick's unit making copy possible as he switches it in and out.

Then a couple of videos of mine. Firstly, just background noise being reduced from S5 to S2. Then a CW QSO where you can see the red LED glow as I switch the unit on and off. The noise reduction is observable, but I would have been able to hear the QSO anyway.

In Nick's example (in a really hostile environment) it was close to being the difference between good copy and none at all.

The noise canceller has been around for quite a while. I'm not sure where the original idea came from but lots of them have been made and the design improved on.

Here is my completed unit in a case.

As you can see, it is a plastic box that really does need to be screened. This was accomplished with the help of the metal tray that last Saturdays barbecue spare ribs came in (and a little self adhesive copper slug tape from the garden centre)..

Nick G8INE managed to find a whole bunch of useful references on the web which are presented below:














Articles (2017)

June 2017
Auto Cut-Off Timer by Bob AE4IC
Saves on batteries.

May 2017
SNA Jr. by DuWayne KV4QB
Unbelievably useful test instrument.

April 2017
Aerial Phasing Noise Canceller
For battling that S9 local noise.

March 2017
QRP for the Tightwad
A Club Talk.

January 2017
A Comb Generator
Handy Wide Band Noise Source.