Hello,
Wednesday night around 2030 pm the WTJR analog Transmitter shut off with a secondary cavity ARC fault. It returned it to air during Richard Roberts Program.
This is the 4th time recently I have seen this fault. It is a terminal fault requiring a trip to the transmitter site to reset. It appears to happen at random and intermittent times.
What this fault is arc in the output cavity or near it.
I detuned the output coupler in the hopes it will give us more head room.
The transmitter needs to be retuned.
We do not have the equipment to do this so I am working on a Harris broadcasting visit this may help eliminate sources of problems.
The tube trolley was removed and the output cavity examined a while back to look for the source, with minor dust and dirt found and no obvious arcing going on.
A cracked air hose was replaced at this time.
Yesterday I tested the arc sensors they are working but this sensor shows a very slow recovery time (2 min)… indicating aging ( most likely it needs replaced ) not a easy job as this is the old design and requires the entire tube and trolley to be rolled out and the output cavity to be disassembled. This may or may not help the situation.
The common causes for this problem are,
1.Lack of air flow
2.Arc across dust or dirt near tube.
3.Problems with the load (transmission line antenna)
4.Faulty Sensor
5.Powerout spike (transmitter power high)
As can be seen by above these conditions still exist here especially #2,3.
In regards to #5. The analog television exciter is acting up with light streaks appearing in the picture from left to right. There is a problem with this unit and it needs to be repaired. I am working on a solution with Harris broadcasting as we have no backup at all for this unit. The frustrating thing here is again its random and intermittent. It is possible that this unit may be emitting high power spikes.
Also the antenna inspection is still pending with the tower crew.. it could be any day now.
We are at 40% power on channel 16 till all this is worked out.
Please Print this out and insert in station log #4
Jim Wilson
Engineering WTJR TV
Quincy, IL
engineering@wtjr.org
WTJR Engineering 