Ed Murlatt & Associates, Inc.
RF Services for the Broadcast Industry
Basic Passive RF System Maintenance
Transmission lines, antennas, filters, combiners, and other passive RF system components are highly reliable portions of the broadcast plant.  However, they don't last forever and failures are often more spectacular due to a general lack of maintenance.  There are some steps you can take to help keep your RF system operating in general good health.
First and foremost - Make certain you have complete mechanical and electrical data on hand at the transmitter site.  This includes detailed drawings for all components, installation drawings, and reference RF sweep data.  The level of the mechanical data available will depend on the manufacturer.  In order to be meaningful, the reference RF sweep data should follow some basic guidelines (click here for more).  If you don't have some or any of this documentation, you should acquire it now.
Make certain the transmission line is pressurized correctly, and keep the pressurization equipment maintained.  Have any leaks located and corrected immediately.  I plan to have more details on pressurization in the near future.
Make certain your annual tower inspection includes checking spring hanger tension, as well as checking to make certain there isn't any missing or rusted hardware.   
Make sure the fans are operational on your filters and loads.  For liquid cooled loads, make certain the coolant is in good condition, of the proper type, and flow is within specification.
Have your RF system swept annually to detect failures before you experience a total burnout.  It is important to have the correct reference data to assist in diagnosing potential failures.  If your reference data doesn't meet the basic guidelines, consider having new reference data recorded soon. 
Know the normal operating temperature range of your RF system.  Some components operate at higher temperaturs than others, and each system has its own thermal signature.  As with some of the swept data, a good reference is critical to determining if a problem is developing.  Use a good quality thermometer to record temperatures of components that operate at elevated temperatures.  If you use an infrared thermometer, make certain to record data at the same location and from the same distance each time.  Also, infrared thermometers can give errant readings from reflective surfaces.  Apply a small spot of paint or black electrical tape to any reflective surfaces you wish to monitor.
Keep a few spare sections of line, a dozen O-rings, some spare insulators, a couple of bullets, and if possible some elbow innards on hand in the event of failiure.
If you are uncertain about any of the information here, wish additional clarification, or have a system specific question with which you'd like assistance, please call or email.