There was a couple of transmitter cutbacks early this morning. I reduced the audio input by 0.1dBu to 7.9dBU. Will be doing some arc gap adjustments this afternoon at the transmitter site.

Upon arrival at the site, I found Benny cleaning about 6 layers of paint off of the ball gap for Ant 4. I had him set the gap to about 0.560″ (about 1/8″ wider than it was). This is the only ball gap that has shown recent signs of arcing and is suspect in causing the VSWR trips when on the south pattern.

I resumed the search for the PA Module test cables. I had called Rich West earlier this morning and he was not aware that there were any, nor where they might be found. When Benny returned to the building, he thought of a couple more places to look without success.

With confidence that everything had checked out properly, I decided to check the repaired module (Ser# H154) using full voltage in the transmitter. The module in position 6 (Ser# H145) was removed to make room for testing the repaired one.

The transmitter was ran at 25kw and the repaired module looked OK. Verification of the repaired module’s performance as done by inhibiting it to see how much the output power dropped. This was then compared to the drop from a couple of ‘good’ modules. The drop was the same, indicating the repaired module was operating properly.

This test was repeated at full power (100kw) with the same results. I then momentarily increased the power to 120 kw without modulation and it continued to preform well. Power was reduced back to the 100 kw in preparation for the evening broadcast.

Tomorrow I plan to return all PA Modules to their original positions.

After taking safety precautions, I went out to Tower 3 to check the gaps and reduced the ball gap to 30mm (1.18″) compared to the 1.75″ that it was before. It is still a little wider than it should be, but did not want to go too far at one time.

I then checked the arc gap inside (antenna tuning unit) ATU 3 more closely than on Friday. There has been a lot of arcing here with melted brass on the grounded ‘point’ (possibly partly caused by the lightning strike that broke the red sidelight glass on top of the tower). I filed off some sharp edges and ‘cleaned’ the arc gap, then increased it to 1.375″ (an increase of 1/8″). I am fairly convinced that this is cause of VSWR trips on the non-directional antenna pattern (NDA).

After completing these adjustments, I tested the transmitter at full power to verify everything was in order for the evening’s transmissions.