QO-100 - RF preamp

In search for a suitable pre-amplifier for the SG-Labs PA V3 I was pointed by a fellow ham to this amplifier on Amazon for abt.€17,-

The advertised gain was 40dB - lets check this out :-)



  • Siglent SSA3021X with tracking generator
  • 40dB attenuator on RF input -> so add 40dB to the measured signal on the SA

Data @ 2.4GHz

Input (dBm)  Gain (db) Output (dBm)
 -20 34,4  -25,6
 -17 34.2 -22,8
-15 33.6 -21.4
-10 30.0 -20.0

Conclusion: Maximum input power @ 2.4GHz is about -20dBm

Data @ 1GHz

Input (dBm)  Gain (db) Output (dBm)
 -20 39.8 -20.2
 -17 37.6 -19.39
-15 35.7 -19.24
-10 30.75 -19.25

Conclusion: Maximum input power @ 1GHz is about -20dBm


The advertised amp gain of 40dB will be nearly reached at least at 1GHz.

The maximum output power of +20dBm (100mW) will be also reached at 1GHz.

At 2.4GHz the maximum output power is abt. 14.4dBm (28mW).

Usability for QO-100 Uplink

 To use this amplifier as a preamplifier in front of the SG Labs V3 PA will result in an (estimated) ouput power of 14W.

Lets check again the real amplifier when it arrives.