Pagina166b

Measuring of highfrequency fields

Measuring of highfrequency electromagnetic fields requires quite different mesuring techniques. Because in this region the electrical- and magnetical fields are intertwined into each other, it is sufficient in measuring only one field. In general we use the electrical field.

HF meters do not work with sensors, but with special antennas, which differ per frequency range and target.
An antenna to measure a quantity is different from one which is used fore bearings.

There are hf meters, which contain AGC, (Automatic Gain Control). These amplify certain weak signals, so they are good audible. The disadvantage is that the sound is not proportional to the real strength or intensity of the signal.
There are now good reliable meters, but they do not have AGC, and one needs to get accustomed to this in order to pick the signals.

Professional

Professionally a Spectrumanalyser is used. It looks at what
signals are at what frequency and measure the strength.
It is a precise and accurate work.
The meter, the antennas and the cables must be verified,
checked, calibrated and approved and calculated with the results.
Despite all this precision, one counts with Spektrumanalyzers
with a deviation of + and - 3 dB, and faults can be made also.

Each found transmitter has its own curve
on the display, and its peak shows the signal
strength.
Examples can be seen on the page of
elektrosmog sources, highfrequent 2

Above the first, the second and the third generation highfrequency meters.
If you want to start, I recommend the Esmog Spion or the HF Analyser HF 32C.
The readable values of the Esmog Spion are not reliable, but one can hear the signals at its best, loud and clear. It has AGC.
The Gigahertz HF 35C has reliable uW/m2 readout in scale A to 200 uW/m2 and scale B to 2000 uW/m2. It separates the average and the peak values of the signals. Signal analysis without AGC.
See also the page *het bitje* for publications.

If one wants to measure highfrequency, it is important ot know:
howmuch radiation there is
from whiche direction it is coming
what kind of radiation it is
which frequentcy

Only when one knows all that, one can ponder upon shielding

Reports about measurements and values in Germany:

bericht_messv_final.pdf | Measurements by Bornkessel, COST 281
MOBILF-1.pdf | measurements in living areas
MOBILFUN.pdf | practical experiences of Wolfgang Maes

Read on Shielding materials 1

Broadband

We deal furtheron with the so-called Broadband measuring equipment. They take everything that is in the specific frequency range, which the meter can handle !, and for which the antennas are suited for. Dependent on the used antennas, there is a great difference in tolerances.

I'll give an example. The HF Digitmeter II is well known by the several
issues of *het bitje*. Standard issue are several dipole antennas,
plus a long extending one. They are good for a large range of frequency
ranges but for radiation quantities not reliable.
In order to know a bit more about the radiation quantities I have a special
measuring antenna, which does not have those deficiencies.
Determining the direction of the transmitters is problematic. That is why I
use a logarithmic periodic directional antenna, which has a narrow angle
and allows very well in finding the precise locations of the transmitters.
That way I can pinpoint the exact location of DECT phones at the houses
of neighbours, sometimes three houses away. Of course the quantity of
the radiation can not measured properly this way.

The range of broadband is very wide, and between my received signals
there are also radio and TV transmitters and other signals, which disturb
the representation of GSM transmitters, or obstruct an analysis.

As an option I do have also magnetical *Schleifenantennas*, which measure hf radiation locally. These locally radiation spots we call *Hot Spots* and they often have the size of a small football.
They form local concentrations of all kinds of highfrequency sources and originate by f.i. reflections, a phenomenon which one should look after very carefully and take into account when measuring HF fields.
On my request Gigahertz Solutions, manufacturer of a wide range of meters for LF and HF has promised me to develop such an antenna for their range of HF meters.
I also have found that certain walls absorb HF radiation and start radiating these as a secondary antenna and reflector.

The newest generation of HF meters, like those of Gigahertz Solutions, which are equipped with a logarithmic periodic antenna, and by which reliable can be measured, do have a sharp input filter starting at 800 MHz, and as a result of that, the signals of radio and TV will be cut off and cannot interfere with the results.

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