- I needed to change the central frequency a little to 2.4 GHz, so I implemented 1.1pF in input side of the RF2126 module instead of 1pF for C1 and C2. To get 1.1pF, two 2.2pF 0805 in series were used.

- 20 dB attenuator at the output of the RF2126 module:

- no attenuator at the output of the RF2126 module:

https://www.amazon.de/-/en/Performance-Linear-Amplifier-Electronic-Accessories/dp/B09Y5XSMJF

Notes

• The second module was modified with the same modifications. Looks OK.
• 10dB attenuator at RF2126 module input improves gain flatness, so seems like the signal generator source impedance is not perfectly equal to 50 Ohm. See the log for the second module modification results.

No attenuator at the input, only a 20dB attenuator at the spectrum analyzer input

10dB attenuator at the input of the RF2126 module

Short/long cable comparison

• 20dB attenuator at the input of the spectrum analyzer.
• The cable length is 150mm (Wuerth RG174/U 65503503515303) from the generator to the input of the module.
• Comparison between 150mm and approx. 1m (RG174) lengths on the output of the module.
• Seems like 1m cable had approx. 1dB of losses.