Copyright ©1998, RF Specialties Group.
A few minutes worth of attention will go a long way with this simple, yet very useful, piece of equipment. Do you keep it clean? Be sure to dust it off occasionally, especially if it is air cooled. If it uses forced air for cooling, blow the unit out so that dust and dirt don't collect on the resistive elements and build up on the blower motors. You change the air filters in the transmitter so it can breathe, right? So be as thoughtful of the dummy load. If you use a coolant-filled load you should "check the oil" periodically. If the level is too low it won't perform properly. Check for leaks if the level is too low, repair any you may find, and add enough oil or coolant to properly fill the load. Don't use anything other than what is specified by the manufacturer, and don't overfill. Doing so might void the warranty on your unit. If your station uses combined transmitters to achieve the desired power output, there is a load on the reject port of the hybrid combiner. Make sure it is capable of handling at least half the output power of the highest power transmitter (both should actually be equal but often are not) going into the combiner. In the event one of the transmitters fails, the load will need to be capable of handling half the output power of the remaining transmitter. Is the load ready to handle the task? That's why they call it a "dummy" load; it usually doesn't tell you anything, you have to check it. You can't always prevent a transmitter failure. But, your dummy load CAN be prepared to handle that situation IF you'll remember to give it a little TLC every now and then.
Stevan
White of our RF Specialties office in Texas has been a chief engineer and operations
manager for stations in Amarillo, Texas. He started in radio as an overnight
DJ while attending the Broadcast Engineering Technology program at Amarillo
College in Amarillo, Texas. He's been with the RF Specialties Group since 1993.
Steve's email address is rfstx@compuserve.com