In this article we compare two types of shielded power cords, the shielded power cords produced by Gigahertz Solutions and the shielded power cords that we have made entirely by hand.
In particular we compare the cables when they are used to power a common computer.
The instrument used is an ME3030B from Gigahertz Solutions, it is an electric and magnetic field meter with sensitivity of 1 V/m and 1 nT in the frequency band 16 Hz - 2 kHz.
Of course all the measures were taken with the same instrument and with the instrument in the same position near the cable, which was with the instrument's box just above the cable and aligned with it.
The following are the measures of electric field.
| PC status | G.S. shielded cable | Our shielded cable |
| on | 3 V/m | 4 V/m |
| off | 2 V/m | 2 V/m |
The following are the measures of magnetic field.
| PC status | G.S. shielded cable | Our shielded cable |
| on | 70 nT | 15 nT |
| off | 20 nT | 3 nT |
There is a noticeable difference between the commercial product from Gigahertz Solutions and our hand made product, in favor of our product, about the magnetic field shielding, while the electric field shielding is almost the same.
In addition, these measures have been taken with an instrument that is sensitive only to the band 16 Hz - 2 KHz so it excludes the higher frequency magnetic fields, like those caused by the switching power supplies.
Even if the commercial shielded power cords block the electric field almost completely, the magnetic shield effectiveness is unsatisfactory. The low frequency magnetic field near the power cord can easily influence other cables like keyboard cable, mouse cable, headphones and microphone cable, loudspeakers cable, and the VGA cable which goes to the monitor, and then these devices will emit low frequency fields, with all the noise that is associated to the mains power.
The difference between our cables and the commercial products with respect to magnetic shielding is huge when another kind of device is attached to the power cord, we will report measures for that in our next article.
Read about measures of EMF from power cords.
Read about problems created by cables in offices.