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Intro
compression levels

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Intro

    The downstairs if/lo 260MHz amplifiers are located in racks 7-17 (left amp) and 8-16 (rightAmp). They are composed of a an 11 db variable attenuator (before the amps) followed by 5 10 db amplifiers.
    The front panel switch is labeled:

• 40: 1 amp inserted
• 30: 2 amps inserted
• 20: 3 amps inserted
• 10: 4 amps inserted
• 0 : 5 amps inserted
  

    They are wide band amplifiers  (not sure the bandwidth since i can't find the drawings :).

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Compression levels:

 
    On 14feb20 the compression levels for the 260MHz amps were measured. The setup was:

• Signal generator outputting 30MHz tone
• 3 db attenuator (using the 1db step attenuator between 0 and 3 db).
  
• at 0 db attenuation there was a .5 db loss at 30 MHz)\
• two cables each with .2 db loss at 30 MHz
  
• hp spectrum analyzer

The cabling was:

• signal generator -> cable (.2db loss) -> variable atten (0,3 db) (.5 db loss at 0db)-> 260 MHz amp input-> cable (.2db loss)-> hp spectrum analyzer

The measurement sequence was

•  Step the signal generator power level in 5db steps from a low level to a high level
• At each step measure the power thru the setup on the spectrum analyzer with the variable attenuator set at 0 and 3db
• To the stepping for the 260 MHz amps set to 0 (all amps in)  and set to 10 (only 4 amps in)
• This was repeated for the left amp and the right amp.

The plots show the output versus input power for the tests (.ps) (.pdf)

• Page 1: amps set to 0 (all amps in)
• Page 2: amps set to 10 ( 1 amp left out of chain).
• Top: output power vs input power
• black: amp in left chassis
• red: amp in right chassis.
• * are the measurements
• Middle: 3db step vs input power
  
• The green dashed lines show a 1db compression.
• Bottom:
• The 2nd and 3rd level harmonics (relative to the input power).
• black, green are the left amp 2nd and 3rd harmonic levels
• red, blue are the left amp 2nd and 3rd harmonic levels.

Summary:

1db compression levels for 260MHz Amps

	inputPwr dbm		outputPwr dbm
ampSetting	amp0	amp10	amp0	amp10
left Amp	-28	-17	24	23
rightAmp	-30	-20	17	16

•  The rightmost amp is compressing about 7 db before the left amp.
• The 2nd harmonic of the right amp is about 10db higher than the left amp.
• You should stay 10db below the 1db compression level if you want no compression.
• When reporting  the power levels, i ignored the .7 db loss through the cables and variable amp.
  

processing: x101/100214/if2260amps.pro