Subelement F: Installation, Maintenance & Repair— Topic 46: Equipment Faults-3
Question 8-46F2
Element 8 (RADAR)In a RADAR unit, if the crystal mixer becomes defective, replace the:
Explanation
The crystal mixer in a RADAR unit is a very sensitive semiconductor diode used for frequency conversion in the receiver. It is extremely vulnerable to damage from high RF power. The TR (Transmit-Receive) tube is a gas-filled switch designed to protect this delicate mixer by rapidly shorting out the receiver input during the powerful transmit pulse, preventing high-power energy from reaching it.
If the crystal mixer fails, it's a strong indication that the TR tube may have also failed or degraded, allowing transmit power to leak through and damage the crystal. Replacing only the crystal without addressing a potentially faulty TR tube would likely lead to immediate failure of the new crystal. Therefore, to ensure proper protection and reliable operation, both the crystal mixer and the TR tube are typically replaced simultaneously.
Related Questions
8-45F6 The indicated distance from your own vessel to a lighthouse is found to be in error. What circuit would you suspect?8-46F1 Silicon crystals are used in RADAR mixer and detector stages. Using an ohmmeter, how might a crystal be checked to determine if it is functional?8-46F3 An increase in magnetron current that coincides with a decrease in power output is an indication of what?8-46F4 It is reported that the RADAR is not receiving small targets. The most likely causes are:8-46F5 A high magnetron current indicates a/an: