Background:

• During the heating campaign the 8 MHz radial element on tower 1 had arcing problems when we were transmitting with the 5 MHz dipoles.
• After the hf run, the 8 MHz radial balun was removed. holes were found in the heliax (toward the top of the balun).
• The heliax going through the balun was replaced.
• On the 3rd day of the oct16 hf campaign, tx 5 failed. It remained offline for the rest of the campaign.
• alfredo and victor have worked on the tx 5 since the campaign.

What we did:

• mesh at 5 MHz reference position.
• use 5.1 MHz, rcp
• we used the 430 MHz ch and the interim correlator to monitor any arcing.
  
• bring all 6 tx up at lower power (25 to 45 KW)
• At 13.3 hrs tx5 was at 40KW. When we increased the power,  power went to 0.
• alfredo said that the tx did not trip, but that the output of stage 2 was not working properly.
• We brought the other 5 tx up to 60 to 70 KW
• The ch spectra showed arcing.
• We then went down to the bowl.
  
• We could here an arcing coming from the 8 MHz radial tower 1 (though not very loud).
• At 13.48 hrs we brought the power of the the 5MHz radial (tower 2) to 0. The arcing stopped.
• At 13.8 hrs - switch to 8 MHz check the reflected power (1 tx at a time) to see if we damaged 8MHz radial tower1
  
• a tx was brought up to about 16 KW and then we measured the reflected power (on the fieldfox).
  

• tx	tower	fwdPwr KW	rvsPwr dbm
  tx1	1 radial	16.9	.27
  tx2	1 tangential	15.6	1.64
  tx3	3 radial	16.9	-0.14
  tx4	3 tangential	15.3	0.11
  tx5	5 radial	rvs power note connected
  tx5	5 tangential	16.8	-4.68

  
  
•  Tx 1 reflected power was no larger than the others.. so it probably isn't damaged (at least  we didn't see it at low power).
• See page 2 of the plots..
  
• Carlo mentioned that the safety cable for tower 1 was passing close to the ground cables of the two elements.
• He  climbed the tower and removed the metal safety cable.
• At 14.7 hours we switched back to 5MHz and brought the 5 transmitters up to 50 to 70 KW.
• We went down to the bowl to listen for arcing from tower 1.. we didn't hear anything
• Looking at the ch monitor, there was still some arcing seen (14.84 hours..).
• see page 3 of the plots..
  

Summary plots of the day (.ps) (.pdf)

• Top frame: transmitted power measured from rf coupler in dbm.
  
• middle frame: transmitted power converted to KW.
• bottom frame:
• colored lines: synth drive level used for each transmitter (dbf)
• red lines. Total power measured from carriage house monitor.
  
• 1 second dumps. Used to check for arcing.
  
• Page 1: 5 MHz 13:00 to 13:42
• this shows when tx 5 failed (13.3 hrs).
• The arcing is seen in the bottom panel (red lines).
• The arcing stopped when we brought tx3 down (13.47)
• Page2 : test 8MHz. 1 dipole element at a time
• We measured the reflected power for each forward power.
  
• Page 3: tx  5 MHz after tower 1 safety cable removed.
• We did not hear arcing down at the bowl.
• The ch monitor still showed some arcing .. but it could have been coming from something else.
• The power level for the test with no safety cable was less than the first test (that showed arcing)...
  
• So maybe we need to crank the power up next time..
  

Summary:

• TX 5 at 5 MHz still has problems.
• The arcing on 8 MHz radial , tower 1 is still occurring when we use the 5 MHz tx.
• the 5 MHz radial on tower 2 is causing the arcing (at least turning it off stops the arcing).
• We did not see high reflected power from tx1 8MHz (twr1 radial which had the arcing) when we used 16 KW.
• so hopefully it is not damaged.
• After removing the safety cable on tower 1 and then transmitting with 5 MHz.
  
• we could no longer hear arcing from the tower
• There was still some arcing seen in the ch data.
• the power for this test was a little lower than the value used to generate the initial arcing.
• initial:  5MHz tower3 radial - 65 KW,
  
• after  : 5MHz tower3 radial  - 60 KW.
  

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