Inhaltsverzeichnis
Rohde & Schwarz Mobile Tester SMFP
Manufactured by Rohde & Schwarz, Munich.
The Mobile Tester SMFP is a compact, complete radio tester from Rohde & Schwarz. In the SMFP version, it is fully equipped, in the SMFS version, some functions are only available as options. The set allows receiver and transmitter measurements, partially automated tests and can be remote controlled from a computer.
Technical data
- Frequency range: 0.4 - 520 MHz (optionally up to 1000 MHz)
- Frequency memory: none
- Output power: CW/FM - 137 to + 13 dBm (0.032 μV - 1 V); AM - 137 to + 7 dBm (0.032 μV - 0.5 V) at 50 Ω
Power supply
- Mains operation: 115 - 125, 220 - 235 V
- Batteries: 11 - 33 V (95 W)
Dimensions
- 470 x 198 x 485 mm, weight 24 kg
Accessories
- SMFS-B9 analogue display: including oscilloscope function to display demodulated signals when performing transmitter tests and AF during receiver test as well as automated sweep of a filter
- SMS B1 reference oscillator: improved frequency accuracy to ± 10^-8/month
- SMFP B2: 1 GHz frequency extension
- SMFP B6: adjacent channel power meter
- The simpler SMFS set can be upgraded to the capabilities of the SMFP with the SMFS B7 AF synthesiser module and a freely adjustable modulation generator and with the SMFS B5 control interface for computer control.
Operation
The Mobile Tester SMFP consists of various components.
For receiver testing, it serves as a signal generator that can be set to an accuracy of 100 Hz in the range 0.4 to 470 MHz. Operation mode is selected using the EMPF button at the top left, the various parameters can be set using buttons in the upper part of the front panel with a light grey background. A frequency can be entered quickly using the numeric keys and by pressing the SIGN GEN key. The level can be set in the form of μV, mV, dBm and dBμV, a signal can be amplified by + 6dB or switched off completely when the HF/RF OFF button is pressed.
The signal can be modulated in different ways: FM, phase modulation or AM (amplitude modulation) can be selected with the buttons on the left, the buttons below the MODULATION display can be used to modulate with an external signal or an internal tone generator can be used to modulate the signal. FM, φM or AM is selected with pushbuttons below the MOD INT button, you can choose between seven fixed modulation frequencies from 300 Hz - 6 kHz using the arrow buttons or enter a freely selectable frequency using the keypad.
The AF signal from the receiver is fed to the SMFP via the AF AC meter BNC socket and the level is shown in the PEGEL LEVEL display and it dan be heard from a small monitor speaker for monitoring.
If the signal generator is set to a specific frequency and connected to the antenna input of the receiver and the AF from the receiver is connected to the AF AC Meter socket, the SMFP can be used to carry out automatic sensitivity measurements. SINAD and S/N (signal / noise ratio) can be measured. For a given frequency and output power, the level can be read using the S/N button; for automatic measurement, the desired S/N level can be entered (e.g. for 10 dB S/N, the button sequence 1 - 0 - S/N), the signal generator starts with a very weak signal and increases the level step by step until the target level is shown on the RESULT display. The sensitivity is shown in dBm on the PEGEL display; the sensitivity can also be calulated to μV by pressing the μV button.
For transmitter testing, a transmitter can be connected to the combined input/output N type socket. The SMFP displays the transmission frequency and the transmission power in W and dBm (from 50 mW to 30 watts) and can also measure adjacent channel emissions. The FRQ.METER input can be used to measure the frequency of a signal (level 10 mV - 1 V) and also the deviation or modulation. When doing a transmitter test, a signal can also be fed to the audio/microphone input of the transmitter via the MOD.GEN output, and the modulation, distortion factor and S/N value of the incoming RF signal can be measured.
The SMFP has a number of special functions. The U/I DC button can be used to measure direct currents and voltages and acts as a volt/ampere meter via four sockets.
Thanks to the functions stored behind the REF button, standardised measurement tasks can be processed repetitively. The SMFP is programmable, can be remote controlled from a computer and could be used as a fully automated radio test set, for example in production control or for checking after repairs. For the Rohde & Schwarz SMFP-K1 software, Rohde recommended the use of the PPC or PUC process controller as a computer and also offered a PUD printer to print out the measurement logs and attach them to the radio for example after a repair or calibration.
For receiver testing, the antenna input of the receiver is connected to the N socket HF RF, the signal from the loudspeaker or headphone output is fed to the BNC socket NF AC Meter, and the sound from the receiver can be heard from the monitor loudspeaker. All functions can be controlled using the buttons, a triangular marker under all digits of the display can be moved using the arrow buttons and changed using the + / - buttons. If the cursor is positioned in a field, a value can be entered using the keypad and accepted using the function key.
For example, to test a shortwave receiver in AM mode, the SMFP is set to receiver test mode using the EMPF and AM buttons. Amplitude modulation is selected with MOD INT and the AM button, „50 - MOD“ sets 50 % amplitude modulation from the internal tone generator, the standard frequency of 1000 Hz can be changed with the arrow buttons. The RF can be interrupted at any time using the HF/RF OFF button.
The desired frequency is entered using the keypad, for 6,000 kHz this would be 6 and SIGN GEN. The output level of the RF is now set, for example with 1 - 0 and μV. The receiver can now be tuned and the 10 μV signal should be clearly audible as a whistle.
The signal is rhythmically modulated when the S/N button is pressed and the RESULT display shows the signal/noise ratio at the set level. For the automated sensitivity test, the S/N ratio to be tested is entered, for example „1 - 0 - S/N“. The set now starts testing with a very low output level, which is gradually increased until the signal/noise ratio is 10 dB. The value can be read in dBm, by pressing the button the display of the value also changes to μV. Pressing S/N again ends the measurement, during which the receiver must not be detuned, as otherwise the SMFP will greatly increase the output power as it assumes an insensitive receiver input. By entering a new frequency, level to locate the signal and pressing 1 - 0 - S/N, the sensitivity is measured at another point within a frequency range or another frequency band of the receiver.
Technical principle
Automatic receiver and transmitter test equipment.
Components
The set is solid state.
As with many R&S sets of this generation, critical areas in the ageing of the set are the power switch, which no longer engages; the plastic lug that engages the switch in the ON state wears out after long use, and replacements for the original switch are no longer available.
The LCD displays are also problematic, in a whole series the potting compound was probably faulty or too thin and the LCD displays become faulty and leak, resulting in black spots and clouds, without replacement of the display, the set is unusable in these cases.