Inhaltsverzeichnis
Rohde & Schwarz SMDA BN 41314
Manufactured by Rohde & Schwarz, Munich.
The signal generator SMDA with its analogue frequency display can be expanded with the SMDF/SMDA frequency controller with a digital frequency display and with a high power measurement adapter to form a complete wireless measuring system.
Technical data
- Frequency memory: none
- Features: Modulation generator 300 Hz to 6 kHz
- Transmit power: 0.1 μV - 1 V resp. - 140 to 0 dBV
Power supply
- Mains operation: 115, 125, 220, 230 V; 22 - 26 V DC
Dimensions
- 484 x 238 x 338 mm, weight 17 kg
Accessories
- Frequency controller SMDF/SMDA BN 413115
- High power measurement adaptor for SMDF/SMDA BN 413116
Operation
The RF signal generator is built into a metal cabinet and, with its 19„ rack width, is significantly smaller than the extra-wide SMFA.
The frequency is set on a drum dial, the entire frequency range from 0.4 - 484 MHz is covered in seven subranges: 0.4 - 48 / 47 - 74.7 / 74 - 129.5 / 129 - 184.5 / 183.5 - 294.5 / 293 - 404 / 401 - 484 MHz. The corresponding sub-range is selected with a pushbutton to the left of the dial. Please note that not all ranges cover the entire dial range, i.e. you can tune below or above a freuqency range, but the oscillator will then no longer oscillate cleanly. For example, if you switch to the next higher frequency range, you may find an empty area of the dial and no clean signal is generated there.
The desired frequency is set using the large tuning knob, the round auxiliary scale on the knob can be turned, and the two coloured lugs are turned upwards to match the colour marking on the frequency dial. The frequency range is displayed in the viewing windows when the fine scale is turned and the distance between two graduation marks is indicated. With the fine frequency adjustment, a small deviation upwards or downwards from a known frequency can be set if the coarse tuning is left unchanged.
The output voltage of the signal generator can be set using the crank knob at the bottom right of the front panel. When turned fully clockwise, the output is set to maximum; when turned anti-clockwise, the signal is attenuated and the corresponding value in (μ/m)V can be read off the dial. The signal can be taken from the N socket below, the input is protected against external (DC) voltages.
The RF signal can be unmodulated (both switches below the instrument in position UNMOD.), amplitude modulated, frequency or phase modulated, combinations are also possible. In the INT. position, the built-in modulation generator is active, which oscillates on frequencies between 0.3 and 6 kHz; frequencies between the fixed values can be set with the FREQ control below. The red centre buttons of the FM and AM switches change the modulation level for AM and the frequency deviation for FM operation. The modulation level (0 - 95 %) or deviation can be displayed with the instrument switch in the corresponding positions marked in red. The signal can also be modulated with external signals that are fed in via the corresponding FM/AM-EXT BNC sockets.
Frequency controller - SMDF / SMDA
The frequency controller is used together with the SMDA and with it, the exact frequency to be read from a red Nixie tube display; the operating mode switch must be set to FREQ.INT. Frequencies can be read with an accuracy of 10 Hz: if the measuring time switch is set to 0.1 sec. on the far right, the reading accuracy is 100 Hz, in the 1 sec. position it is 10 Hz. The first digit is cut off for frequencies above 100 MHz and the display is moved one digit to the left so that the 10 Hz digit can be displayed. At first, the display with the missing first digit may look like a malfunction, but with the switch set to 0.1 sec. the frequency display is correct.
Even in areas outside the frequency markings in certain ranges, the display can be misleading; according to the manual, these can be recognised by the fact that the display is not stable - so you can only trust the display in the ranges in which the frequency dial of the SMDA has frequency marks.
The SMDA and the frequency controller can be operated in synchronised mode. After pressing the SYNCHRONISATION button, the instrument pointer is moved to the black marked area in the centre with the fine tuning of the transmitter. You can now leave the tuning on the SMDA and make small frequency changes on the controller using the FREQ.FEIN control; the grey button is used for coarser tuning and the central red button for finer tuning.
The operating mode switch on FREQ.EXT.B can be used to measure frequencies applied to input B with a level between 0.3 and 3 V in the 1 - 490 MHz range, while the operating mode switch on FREQ.EXT.A can be used to measure frequencies fed into input A in the low frequency range between 50 Hz and 5 MHz.
The operating instructions provide information on deviation measurements of frequency and phase-modulated signals.
Technical principle
RF signal generator, amplitude modulation 0 - 95 %, frequency modulation 0 - ± 75 kHz, built-in AF modulation generator
Components
The set is fully solid state.
Technical documentation
- Rohde Schwarz SMDA repair instructions, german - please enquire by email if required
- Rohde Schwarz frequency controller for SMDA repair instructions, german - please enquire by email if required
