Measuring the Sband transmitter power

Overview:

The continental power measurement.

• the rf signal is taken from a directional coupler after the comber (see dana's schematic).
  
• The signal is detected and the  the voltage from the detected power is returned via the TTI_8 analog input module (schematic 190162 XA08) word 08.
• The 732.c program processes and displays the value
• the variable meter[23] holds the input value
• the input voltage in converted to power in the routine: metering (in metring9.c)
• metring9  calls  rfpwr3 (in math9.c)
• rfpwr3 converts voltage to watts with a lookup table
• the returned value in meter[23] is then scaled by scale[23]/1.c0000. (2400/10000) to put the value in Kwatts.
• The voltage to watts lookup table was changed by phil on 11feb04
• jon hagen measured a new set of values which were then installed in rfpwr3().
  
• The old table is accessible in the routine rfpwr33. this routine is only there for reference.
• The rfpwr3() lookup table is used also used for the kly1,kly2,and waster forward power measurements.
  

The lro power meter.

• The lro power meter was installed around 17nov11.
• dana's schematic shows the connections. It uses the 2nd port of the continental coupler.
• The power is read by the monLro  program running on the da crate (/home/phil/vw/datatk/mon/monLro.c)
• It reads the power meter via the gpib bus that goes up to the dome.
  
• The program records the power every 10 seconds. It writes to the file /share/obs4/lro/pwrdata.log.000
• The output is ascii   mjd.fract   dbmPower
• Sometimes there are some extra ^@@@ at the beginning of each line
• The dbm power has +/- in front of the number. Sometimes this sign gets dropped. Just look at the numbers around it to see what the sign should be.
• There is 82.8db attenuation (as of aug12). add this to get the measured dbm.
• The users starts, stops the lro power meter from the vw% prompt on the da crate
• the tcl procedure: monlro
• helpdt monlro      to get a description
  
• source: /home/online/Tcl/Proc/gen/monrlo.proc
• doc: /home/online/Tcl/Help/monrlo.help
  

Measurements:

• 18nov11: comparing sband 723.c "ant" power reading with the lro power meter (.ps) (.pdf)

• This plots lro power vs continental power.
  
• at fit was done to the data points giving:
• lroPwrKw=19.68 + 78238*antP + .000605475*(antP)^2    where antP is the continental measurement.
• The continental power meter was re-calibrated between nov11 and jul12.
• 31jul12: comparing sband 723.c "ant" power reading with the lro power meter (.ps) (.pdf)
• fit: lroPwrKw=-5.771 + .86078*antP + .000324966*(antP)^2

• 07aug12: Plotting the power vs detected voltage lookup table (.ps) (.pdf)
• I took the current and old lookup tables from the 732.c program and plotted power vs voltage.
  
• The black curve is the conversion from voltage to power table installed 11feb04.
• The green curve is the original voltage to power table that came from continental.
• The green line shows what the lro power reading would be given the black line.
• You can see that the old red table is a closer match to the lro values than the current black line.
• processing: x101/120807/sbpwr.c
  

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