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QRM in you SSB

Feb 17, 2006
4,940
Lancer 27PS MCB Camp Pendleton KF6BL
QRM, or better known as man-made interference, in your SSB prevents you from really hearing weak signals. Some of the QRM is generated by electrical items such as motors, solar controllers, LED Nav lights, refers, and other items. This interference is usually recognized as a popping or clicking sound. So, how do we fix this interference? Well, you have at a minimum two options; find and eliminate the source of the noise, or, combat the noise by adding the same noise but out of phase.

This is known as X-Phase or cross phase. The theory is that taking two occurrences of the same noise, reverse the phase of one of them, and then add the amplitude of the two will cancel the noise. There are devices that will do this for you called X-Phase QRM Eliminator. These can be purchased here in the US from MFJ Enterprises, or purchased from eBay.

Now, I have not personally tried this devise but I will order one soon. I have installed solar panels on my house and now the low bands on my radio are all but useless. The controller noise and panel circular connections basically make an antenna spewing RFI galore.

Here is a link to a review of a X-Phase QRM Eliminator. The review also contains a video demonstrating how effective it is.

So briefly let me explain how this works. The QRM Eliminator goes between the radio and the tuner. The box is limited to 100 watts, but I am sure 150 watts SSB will not harm it. However, power for data connections should be reduced.

OK, with the box connected between the radio and the tuner, you will see one more jack called AUX, or NOISE. This jack is connected to another antenna in the boat. The manual says 2 to 5 meter (6 to 16 ft) length of wire. I am sure that in the boat it can be shorter. Experiment with length. Now, this is not a transmit antenna. It is only used to pick up the QRM, or interference.

There are three controls on the front. Two each, one for the main antenna and one for the noise antenna, and a phase adjustment. The two antenna adjustments are for the gain. What we want is the unity the gain of both antennas. Once that is done, then the phase can be adjusted to null out the interference.

When we transmit, there are relays that will sense the RF and take the QRM Eliminator out of the signal path. Go back to receive and the QRM Eliminator kicks back in.

Again, I do not have one. I am just describing the theory of how it works. I ordered one from Ukraine for $76 and it will take about a month to get here. I am patient. Once I get it, I will try it out and then move it to the boat for testing.

All this is JMHO.
 
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