Background:

• Problems during previous test  14Feb17:
• rf switches at tx.
  
• they were causing all of the power levels to jump around. They were removed noon on 14feb17.
  
• tx 4
  
• tripped once then came back up and ran the rest of the day
• tx 2:
• output power jumped by 3db a few times.
• When the jumps occurred, we also saw the broad band outputs jumped.

What we did:

• mesh was at 8MHz position. used 8 MHz rcp , freq=8.175 MHz.
• telescope position start: az 285 then moved to az=348, chza=0,grza=11
  
• ch only. 430 transmitter was used. ch -> echotek (5.5,9.5) and ch -> usrp.
• Interim correlator not used to monitor arcing..
  
• The interim correlator monitored the arcing using the ch receiver. It also had the 430 tx sample in the spectra.
• 09:22  430 tx brought up.
  
• 09:42 start to bring up hf txs.
• 
  
• 10:15 50KW each tx. stay here for about .5 hours
• sampled tx power much noisier than before . Jumps around by > 1db.
• 10:54  70KW each tx.
• 11:14  disable hf tx, move az 285 to 348.
• 11:18 back up to 70KW.. leave drive levels unchanged till 14:00
• tx4 output unstable moving around be .5 to 1db
• 13:xx started measuring  tx monitor port outputs with scope
• order: tx2,1,3 skip4, 5,6  
  
• 14:22 tx4 broad band replaced
• 14:xx measure tx monitor ports for tx4 (after new broad band installed).
• 14:37 start auto toggle 2 sec on  4 sec off. 50KW per tx
  
• 14:39 stop auto toggle. raise tx power to 60 to 70 KW
• 14:41  auto toggle back on 2sec on , 4 sec off
• 15:09  auto toggle off, 430 tx off
  
• 15:11  adjust tx 4 up to 65 KW then sit at CW till 15:30
• go under bowl to check out any arcing
  
• tx 4 still wandering around (even with different broad band).
  
• 15:30  hf off.
  

Plots of output and drive power:

The plots show the data we took while the hf was on (.ps) (.pdf)

• The page has 3 frames:
• each color is a different transmitter (1 through 6).
  
• top  frame: rf power (in dbm) measured at the output of the rf coupler.
• middle frame: the same output power, but displayed in KWatts
• bottom frame:
• The synthesizer drive amplitude used
• The dashed green line shows when the rf was on
• the red line at the bottom is the total power from the carriage house 430 receiver (polA 425-435 MHz). When we have arcing, there are jumps in this power (rfi can also make jumps).
• 10. to 11.0 bring power up to 70KW
• 11.5 to 14 : 2nd frame. blue trace tx 4 is jumping around and output power is declining.
• 14.0 to 14.3   tx 4 broad band replaced
• 14.6 to 15.1   auto toggle 2sec on , 4 sec off
• 15.1 to 15.5   sitting at fixed output power. tx4 still jumps around.
  
• 15.5  hf off

Plotting the monitor port outputs

• tx3 and tx4 have a phase shift relative to the other 4 tx.
• This shift was visible back in 2015 using the 5 mhz system.
  
• The shift shows up in the IP ANODE output (the shift may be occurring in the network connecting broad band output to the IPA input.
• Dana guessed that the switches that disabled the unused filters in the network were not getting terminated properly.
• The phase for rcp,lcp was computing using the forward power outputs. this includes these phase shifts. If there is an attempt to correct this phase shift, the phases for the polarizations will need to be remeasured.
  

clp movie during hf test

     The 430 clp data from the carriage was processed and  a movies were made. They showed how often arcing appeared.

links to the movies:

Setup:

•  ch at za=0, looking through the heated volume
• 10ms ipp, 440 usec rf pulse data taken for entire run.
  
• echotek:
• ch, 3 to 10 MHz were covered (upshifted)
• usrp:
• ch, 25 mhz about 430 mhz.
• When processing the data
• the rfi removal algorithm was not used (didn't want to clip the enhanced plasma line).
• Each frame of the movie was a 10 second integration.

• 20:14 -> fof2 above 8.175 MHz. saw strong enhanced plasma line.
• a ham repeater was operating around 440.25  for part of the time.
  
• Images of the plasma line
• in both the usrp and the echotek data there is an image of the plasma line shifted by +/- 8.175MHz,. It is only there when the heater is on.

Summary:

• tx4 output was wandering around
• The broadband for tx4 was replaced. it looks like the wandering continued, so the problem may not be the broadband.
• The monitor ports for the 6 tx were recorded and plotted. tx3 and tx4 showed a phase shift (relative to the other tx) at the IPA anode output.
  
• We continued to see images of the plasma line offset by the heater frequency. It is only seen when the heater is on.]
• We had extremely strong enhanced plasma lines at 8.175 MHz.
  

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