ETS-Lindgren 4630 Refrad Reference Radiator (Archived) - Manual (Page 15)

MODEL 4630 REFRAD REFERENCE RADIATOR APPLICATIONS
© EMC TEST SYSTEMS, L.P. – MARCH 2002 11
REV F – PN 399214
CABLE LOSS
The cable loss D
K
is the difference between two measurements of
the receiver power level.
D
K
(dB) = P
O
(dBm) – P
K
(dBm)
P
O
is measured with the comb generator connect to the test receiver
via the 30 dB attenuator. For the measurement of P
K
, both the
cable and the 30 dB attenuator are connected between the comb
generator and receiver.
CHAMBER FACTOR
The chamber factor is intended for the testing of absorber – lined
chambers, where the +/- 4 dB – tolerance given by ANSI and
CISPR is exceeded in the frequency range of 30 MHz
approximately 200 MHz. Chamber factors are determined by
comparison measurements with a standard open area test site.
The REFRAD acts as a field-strength transfer standard. It is
operated separately with both the dipole and the loop transmit
antennas. This is necessary in order to generate both fields having
a high wave impedance in the near-field of the source and fields
having a low wave impedance.
The reflection loss of common broadband pyramidal absorber
material is a function of the wave impedance. This procedure,
therefore, simulates extreme cases of possible characteristics of
equipment under test.
The “volume method” given by ANSI and CISPR is applied
similar to the NSA measurement. For each point, a comparison
measurement is carried out using the dipole as the transmit antenna
and another measurement using the loop. Each of these comparison
measurements yields a correction factor. When all of the correction
factors for one polarization are plotted onto one graph, a typical
spread is found at each frequency. The upper envelope curve of the
Archived 3/18/10