Tom and Joshua King delayed their return home to the U.S. until tomorrow to allow more time to fine tune the antenna system.  We have not worked previous Saturdays, but we thought it best to do so this Saturday starting at 8:30 am–that’s the time the 100,000 watt AM transmitter signs off.

Tom and Joshua making minor adjustments in the phasor room

Tom and Joshua started fine tuning in the phasor room, while I continued trying to find what could be causing the 270 kw limit mentioned yesterday.  I decided to check the tightness of all the RF (radio frequency) power connections inside the transmitter and to make sure there were no tools or packing materials left in the transmitter.  It is possible that either of these could be the cause.  I only found one connection, out of hundreds, that was loose and it could only be tightened less than 1/4 turn.  Result–no change in 270kw limit!

One bolt on the left side of the capacitor on the top right needed slight tightening.

Next, Daryl and I bypassed the antenna/dummy load switch to see if that could be the source of the problem.  Result–no change in 270kw limit!

It was noticed that the new transmitter was showing that the dummy load was not as good a match as some of the antenna selections.  I asked Tom, whose company manufactured this dummy load, whether it was adjustable.  Tom said the it could, so we removed a side panel of the dummy load only to find the adjustment capacitor was not there!  It seems the padded box containing the capacitor was not clearly marked as being for the dummy load, so it ended up being stored as a spare part.  After Tom installed this capacitor, the matching and reflected power was considerably improved.  Result–still no change in 270 kw limit!

When we opened the dummy load side panel the place where the tuning capacitor was supposed to be located was empty. Notice the hundreds of load resistors to each side.

Tom and Joshua continued to fine tune the antenna system and managed to adjust all three patterns to within 2% of 50 ohms– a very good match!!

Tom and Joshua reviewing the results of the change just made.

The transmitter’s computer readout does not agree with Tom’s measurements and indicates the matches to be closer to 45 ohms.  The above 50 ohm readings were from using a network analyzer (seen in above photo).  As another way to do the same measurement, we decided to use an operating impedance bridge  utilizing 5 kw of transmitter power.  Tom and Joshua made the measurements and confirmed that the 50 ohm measurements from the network analyzer were indeed accurate.   We need to ask Nautel why their transmitter measurements are different.

Joshua and Tom using the Operating Impedance Bridge to confirm the impedances of the three antenna configurations.

The time was now 7 pm.  Tom and Joshua began packing all their specialized equipment in preparation for leaving tomorrow.  Tom decided to store some of it at the transmitter site as he is returning next week with his wife for the dedication.  That way it will be here if further measurements are desired.  He can then take it back on that return trip.

Got back to the duplex about 7:30 pm.  Virginia made baked spaghetti and garlic bread for supper and took some to share with Tom and Joshua.  They plan to return to the site around 8:30 to see if they can observe an arc trip that seems to occur every evening about that time.

I worked on our blog until 11:30 pm and made some progress on getting it up-to-date.