The unit is designed to act as a final stage driving a radiating system, or as an intermediate stage in a chain of amplifiers, thus loaded by the input stage of a subsequent amplifier. Do not handle the unit in any way unless all its protective panels are fully closed and it is connected to a good ground which can ground parasitic currents circulating in the chassis. Do not open the unit for internal inspection of any kind unless the power supply cable is disconnected from the supply and all other connections to other equipment are also disconnected.
If, during a visual inspection, any components reveal themselves to be damaged, broken or incomplete, proceed with extreme caution to avoid contact with the hands or any other part of the body. The main components of the radio frequency unit contain the highly dangerous substance, Beryllium oxide. This is in light of the fact that in addition to the electrical connections required, the sheer physical weight of the unit will not allow a single person to install the unit with complete safety.
The device contains a sophisticated set of supervisory circuits that monitor the operation of the RF circuits in order to maximize operational life and minimize downtime and operator intervention. Control of the stabilized voltage is done by a microcontroller which controls the output voltage as a function of the RF power being developed. The microcontroller on the power supply card monitors the safety of the RF power modules; in case the parameters go outside their limits, it will reduce the voltage supplied to the modules and therefore the total RF power.
The microcontroller's program can be partially customized at the customer's request to adapt it to local operating requirements.
USER INTERFACE
REMOTE INTERFACE
INSTALLATION
When all the equipment is connected and all panels are closed, the units can be switched on in the following order: first the final stage the entire transmitter system, then the intermediate stages and finally the modulator. If the system is configured with the SF150 as the final stage, the modulator must be adjusted to regulate the output power of the SF150 amplifier to comply with the terms of the homologation license for the relevant site. It will clearly be necessary to test not only the correct operation of the system, but also the compliance with parameters with transmission regulations.
If the SF150 is instead an intermediate stage of a more complex transmitter, the final stage calibration instructions should be followed to ensure that the SF150 is not at risk of damage from other devices in the system. The SF150 amplifier has no setting for tuning or other parameters; from a functional point of view it is passive. The operator using the SF150 is therefore only concerned with ensuring that the limits of safe operation are not exceeded indefinitely: the modulator must not exceed the permissible level of excitation power, including situations where environmental factors reduce performance; for sequential stages, the operator must perform calibration of the input stages to ensure safe levels of reflected power displayed by the SF150 meter.
For safety limits on all operational parameters, see the table of typical and maximum specifications. The SF150 features internal circuitry that automatically reduces the output power if other parameters go outside the limits of safety. The operator responsible for calibration may temporarily exceed some of the limits, but must not leave the site with the unit indicating Automatic Power Control (flashing lights on the front panel).
In this case, the stability of the RF output power is not guaranteed (see the chapters entitled TECHNICAL DESCRIPTION and USER INTERFACE of the SF150 manual). Consult the table of typical operating parameters and their safety limits for the SF150 and other related equipment to ensure that the installation operations have been completed.
FRONT PANEL DIAGNOSTICS
- Diagnostic with selector in VOLTAGE position
- indicates that the amplifier is in STAND BY mode as a result of operator intervention or control by external equipment
- Indicates that the unit is ready to generate RF power
- Indicates faulty connection or operating sequence. Confirmed by the Ab message
For any such occurrence, the amplifier will shut down for 7 seconds before trying again. Quite common in this case is the breakdown of the thermal insulator of one of the power transistors of the series regulator. A5: This code appears when there are problems with the RF output of the amplifier, especially when there are sporadic changes in output power.
If the modulator is a frequency conversion type, interference with the radio link receiver's squelch function can cause problems. A6: This code appears when there are problems with the amplifier's RF output, particularly when there is a sporadic or persistent mismatch with the radiating system or subsequent amplifier stage. For each occurrence of this alarm condition, the amplifier will shut down for 7 seconds and will then attempt an automatic reset.
When the amplifier is driving a thermionic tube stage, this alarm condition can occur during the tuning phase of the input, or when the tube is either very new or near the end of its life. A7: This code appears when there are thermal problems with the amplifier, especially excessive heating of the heatsink on which the RF modules and power supply are mounted. Check the output of the amplifier; if the RF load is abnormal, overheating may occur.
This code appears when the amplifier is in STAND BY mode due to operator intervention or control from other equipment. Make sure the modulator is connected to the AUX SUPPLY jack on the back of the device. AC: This code appears when there is no voltage on the input of the power board.
Check the input circuits of the power supply card; the most likely cause is a short circuit. AD: This code indicates that the 'syncro' circuit of the power supply card is not synchronizing with line frequency; the unit is faulty. If, when this sequence is finished, the segments of the alphanumeric display light up in a rotating sequence, the unit is faulty.
TROUBLESHOOTING
Check the front panel for flashing indicators; the instability is due to the reduced operating capacity of the internal protection circuits which avoid an indefinite reduction in power but do not guarantee stability. Remove the cause of the automatic power control intervention by checking environmental conditions or connections to other equipment as indicated, according to the parameter indicated on the front panel. Furthermore, check that the instability is not generated by the modulator, but is reflected by the SF150.
Even consecutive phases can cause power instability. this can happen if the load presented to the unit is unstable or has a high content of harmonic or spurious radio frequencies. Check for harmonic and out-of-band RF content present between the SF150 and downstream devices. Check that the connectors of the radiant system and the successive stage are not damaged or damaged.
Check that the modulator does not generate instability with sudden current fluctuations or even large carrier frequency fluctuations. Check that the modulation frequency deviation is not excessive or that the frequency synthesizer does not lose control. Check the bandwidth of any selective filter attached to the output of the unit; if the frequency deviation is greater than the calibration, the transmitter cannot function properly.
Check that the radio link receiver does not destabilize the modulator during the squelch operation. Many difficult problems can be solved with low-cost solutions: connecting the input filter to the SF150 with the same transfer function as the output filter; powering the modulator and SF150 via mains interference filters; supply of equipment via stabilizers with power reserve.
TOP VIEW
BOTTOM VIEW
F. BLOCK DIAGRAM
POWER SUPPLY and MEASUREMENT BLOCK DIAGRAM
PART LIST OF POWER SUPPLY AND MEASUREMENT BLOCK DIAGRAM
ESPL02 (Power measurement Board)