Hints

Tips and hints

Finding QRM source

Two loops can help you to find the QRM source (beware of coupling with other antennas and object). When nulled, from the QRM source point of view both loops must have the same angle.

Loop as a reference antenna

When working on your other antennas you can use the loop as a reference antenna. When for example exchanging antenna tuners, you can measure the difference in receive signal strength for both tuners. And so determine (an estimation) the difference is loss between the tuners.

Is the QRM source local?

Not all QRM is local. When noise cancelling gives you not the expected attenuation of the QRM, or again and again only during a short while, then the QRM is not local.

Amplifier with a short dipole instead of the loop

The amplifier can also be used on the higher bands with a short (2 ´ 1 meter) dipole.

The lower bands need tuning (coil) in the dipole.

Using smallband/tuned loops

In principle this is possible. The main problem however is controlling the phase difference between the loops. When both (identical) loops are tuned exactly to the same frequency the phase difference (time delay) is defined only by the distance between the loops. As should be.

But when the resonance frequencies of the loops are not the same, the phase difference becomes frequency dependent. When the bandwidth of the loops is very small even within the 3kHz used for SSB the phase difference varies over this 3kHz and can not be neglected.

This considerably degrades the noise cancelling depth and the properties of the loops in an array.

Last updated: September 24, 2006