Manual FCKL 1528 page - 24
13 Function
13.1 Basics of development
It all began with manually operated in-
terference measurement receivers with a
conventional meter to read
measurement. These receivers
dominated the market for several
decades. Due to their simplicity (few
components) and the concentration on
the important features these receivers
were relatively small, light weight,
reliable, cheap and easy to use. Many of
these Schwarzbeck receivers are still in
use and estimated very high by the
users.
Recent electronic development however
made front panel operation more
convenient and introduced pc-control.
timated very high by the users.
13.2 Basic function
The FCKL 1528 is a interference meas-
urement receiver for 2 bands (frequency
ranges). These are CISPR 3 (vlf) 9 kHz-
150 kHz with 200 Hz 6-dB bandwidth and
CISPR 1 (hf) 150 kHz-30 MHz with 9 kHz
6-dB-bandwidth (also described in VDE
0876 and CISPR publication 16.
The receiver's frequency can be tuned by
an optical encoder on the front panel.
The changes concerning the 2 band are
automatically on 150 kHz. This concerns
bandwidth, charge and discharge time of
the quasi-peak detector, the calibration
generator and the frequency steps. An
info range permits an overview with band
B standards down to 100 Hz. Using the
automatic scanning procedure with a xy-
recorder the receiver records a spectrum
in one range from 9 kHz-30 MHz.
The frequency steps change automati-
cally and the scan speed is adapted to
the spectrum to come by variscan. So no
additional adjustments are needed.
One single rotary switch determines
manual tuning or scanning and provides
for setting of the corner frequencies to
adjust the xy recorder.
The desired input voltage range is de-
termined by programmable step
attenuator from 0 dB
µ
V to 105 dB
µ
V in
1 dB steps. In this way both high
sensitivity (below 1
µ
V) and overload
protection against spikes coming from
L.I.S.N.s are achieved. This input
protection is made by a 10 dB power
attenuator directly at the receiver's input.
The 3 digit display (plus sign) includes
the attenuation of the power attenuator,
the i. f.-attenuation and the correction for
the active magnetic antenna FMZB.
13.2.1 Receiver unit
The receiver unit of the FCKL 1528
begins at the input connector and ends at
the active demodulator, The power
attenuator, the step attenuator, the input
filters, the active part and the frequency
synthesiser generating all frequencies
belong to this unit.
13.2.2 Calibration generator
This unit generates the reference signal
for the calibration in all standards.
The signal is generated for the 2 different
standards band A and B.
13.2.3 Indication unit
It consists of the detectors, the measur-
ing amplifiers, the automatic calibration
and many other circuits.
13.2.4 Control logic
The control logic consists of the front
panel board with all controls and displays
and two back boards.
13.2.5 Power supply
The power supply provides for all volt-
ages. + 12 V and - 12 V can be tapped
on the rear side sub-d-connector for
accessories.
13.2.6 IEEE interface
Converts the bus signals in control sig-
nals for the control logic. Part of this unit
is a 12 bit a/d converter. It converts
directly the meter voltage for PC and
software.