Not that I have very much QRM problems here, but I live in an urban area so there is always some of it. Sometimes there is a level of S7-S9.
Fortunately, it is not always that loud and it is not always present. Despite many searches in neighborhood, I have not yet succeeded in locating it.
So I was looking for a way to suppress this QRM. Now there are many so-called "Noise Canceler" on the marked, commercial and homebrew.
Since this is for me an experiment I did not want to spend too much money on it. Finally, I'm not sure if it will work so it had to be "Home Made".
On the DARC website I came across a diagram of DK9NL - Hanns W.
The principle is based the fact that the interfering signal coming from the main antenna is the local interfering signal superimposed by an auxiliary antenna phase that
are canceled interference.
It seemed to me a fairly simple circuit that was easy to build myself.
To make it easy DH4YM - Dirk has a PCB-service where you can order the board.
He provides a nice, completely drilled board for a fair amateur price. There are no special or SMD components used.
Most could be found in the junkbox and otherwise at your local shop and of course, on the Internet.
OM Dirk sent me the pcb (V1.4), along with a parts list and the component layout. There are some minor changes between V1.1 and V1.4.
The main change is that the two relays are not longer parallel but in series. Therefore there are no 12 Volt but 6 Volt copies required.
The results of the X-Phase are very dependent on the location of the auxiliary antenna. When this antenna receives enough QRM, but NOT the wanted signal, the results are pretty good.
It is possible to almost completely eliminate the noise. The point is to make the auxiliary antenna not too large and to place it relatively close to the source of interference.
A two inch piece of wire was sufficient for me in order to eliminate the interference from a bad laptop power supply.
Reason enough to experimenting with antennas to achieve maximum results. On YouTube you will find enough videos to see the effect on, for example, Power Line Communication (PLC).
For me it was a nice little project and will certainly be useful in certain circumstances.
I have not used the above X-phase for so long. I didn't really have so much interference and I could also make another amateur happy with it. So get I rid of it.
But over time I did regret it at some point. Times are changing and more and more solar panels are being introduced, with all the consequences that entails.
At the beginning of 2023, Mans Jansen, PA0MBJ came to our VERON section to give a lecture about the X-phase, which was improved.
Originally designed by G4WMX and GW3DIX, improved by DK9NL. This version of the unit is based on the design of DG0KW.
A slightly different design than my previous one, with other components had to make this device work better and there were some more built-in safety protections.
Mans also claimed that this version achieves a decent result in suppressing solar panel interference.
This is a complete kit, but all individual parts can also be ordered separately. Even a completely built and tested device is available for a small extra charge.
Because I wanted to try it again, I ordered a complete kit. The assembly is fairly easy for anyone to do and the operation is also simple after some practice.
The results are quite reasonable. The interference from the panels has not always been completely suppressed, but let me say 80 percent so a decent QSO is possible again.
All necessary information about this QRM Killer can be found on the website of VERON section A34
