Background:

• We needed to test how bad the harmonic output level was when we input 2 tones directly into the broadband amplifier. We had previously measured the harmonics when sending 2 tones through dana's phase shifter and then into the tx. This had very high harmonics since the two tones were both applied to the lo input of a mixer.
  

What we did:

• The mesh was in the 5 MHz position
  
• we transmitted at 5.125 MHz rcp.
• no 430 tx,
  
• interim correlator recorded  gr 430 receiver to check for arcing
• 
  
• 11:54 50 kw each tx
• 12:00 up to 450 KW. left running to check for stability
• 12:24 stopped so christiano could give a platform tour !!!!
• 13:20 started 2 tone test.
  
• 13:26 -7 -7 siggen drive,
  
• 13:25 off
• 13:29 -4,-4 siggen drive (into combiner,filter)
• 13:31 off
• 13:32 -3,-3 siggen drive
• 13:34 off
• 13:35 -2,-2 siggen drive
• 13:37 off
• 13:39   operator error, skip
• 13:42 -1,-1 dbm siggen drive
• off
• 13:45:30   tried 0,0 dbm.. but tx tripped.
• 14:04  airline trip
• 14:12  bring up . lots of arcing
• toggled a few broad bands off, on to stop arcing.. mainly tx 6
• 14:14 75KW each tx..
• 14:18  arcing tx 6 off,on stopped arcing
• 14:20 arcing tx 1 off,on stopped arcing
• 14:23 arcing. tx 4 off on  stopped
  
• 14:30  done
  

HF output power

Plots showing hf tx drive and output power (.ps) (.pdf)

• page 1:
• Top: hf rf coupler output vs hour of day
• Each color is a different tx.
• middle: output power in KW
• bottom: synth drive amplitude (in dbf)
• page 2: hf drive power vs hf output power
• the output power (in KW) vs input drive power (in dbf) is plotted for each tx.
• values that lie below the trend, occur when an rf off occurs during a spectrum analyzer power average.
  
• 
  

• dbf Drive for 50 KW output.. 5MHz

  tx	dbf drive
  1	-6
  2	-12
  3	-9
  4	-11
  5	-6
  6	-9

  
  

Generator power vs hf output.

    The data from the 3 running generators was used to measure how much generator power was needed to drive the 6 hf transmitters.

Generator output power vs hf output power (.ps) (.pdf)

• Top: generator output power vs time.
• middle: total rf output from 6  hf tx
• bottom: gen power vs hftx output power

2 tone test

    We tested the harmonics generated on output when we input 2 tones directly into the broad band input
The setup was:

• siggen 1: 5.115 Mhz
• siggen 2: 5.125 Mhz  (delta=  10Khz)
• we varied the output amplitude of the the two siggens.
• cabling:
• siggen1,siggen2  combined in a splitter -> 5 Mhz filter -> tx 3 cable to broadband
• We measured the loss through the combiner, filter.
• 4.2 db loss.. so -5 dbm out of each siggen gave -9.2 dbm   for each tone on the spectrum analyzer (before begin sent to the broad band)

The observing cycle was:

• -7 dbm each siggen output
• -4 dbm each siggen output
• -3 dbm each siggen output
• -2 dbm each siggen output
• -1 dbm each siggen output
• 0 dbm each siggen output .. but tx  3 tripped (probably exceeded the power level)

Plots showing the harmonic levels from the 2 tone input. measured at the rf coupler (tx output) (.ps) (.pdf)

• Page 1: rf coupler output in dbm
• Each frame is a different 2 tone drive level (the levels are for a single tone)
• Each color is a different Tx. Green tx3 had the 2 tones. All the tx coupled from the dipoles back into the rf couplers.
• The dashed horizontal lines are spaced every 10 db.
• The tones are at 5.115 and 5.125 Mhz.
• for the stronger drive levels 3*f0 - 2*f1 is stronger than 2f0-f1.
• Page 2: tx output power in KW (linear scale)
  
• Only tx3 tone power is visible. All the harmonics are less that 1 KW.
• Page 3: The harmonic levels for each tone output power
• each frame overplots the harmonics from all 6 tx.
• You can see the harmonics from tx3 and the coupling levels into the other dipoles.
• In general tx4 (dipole 90 from tx3 on the same tower) has the lowest coupling.
• Page 4: single tone output power vs broadband single tone input.
• The dashed horizontal lines are spaced every 5KW.
• The max value was 47 Kw for 1 tone
• This was for -1 dbm drive at siggen.
  
• 2*47 = 94KW total tx output
  
• When 0dbm siggen drive was tried, it tripped tx3. The output was over 100KW.
  
• For the last few db drive increase, the output power is not increasing as fast as the input..while the harmonics increase.
  

Summary:

• For the highest single tone output level (47.6 KW) the harmonics were 20 db down
• For 46 KW single tone output, the harmonics are down 25 db.
  

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