Instability Problem in LNA

[nuddin]

Hi all,
I have designed an LNA at 145MHz using transistor ATF54143. I have simulated the circuit in ADS with S21=19dB, S11=-20dB, S22=-15dB, k>5 for a wide frequency band, NF=0.3dB.

After realization in FR4 PCB, I have a strange instability problem. It is unstable when powering, but it shows expected gain when I just touch the source pin to ground although the source pin seems well soldered and connected to ground via small inductance.
I am attatching the circuit diagram.

Could anyone give me some idea what might be the cause of such problem.

thanks in advance

nuddin

 

[dgnani]

Don't know much about RF design but if touching fixes it, you either need a cap or a ferrite on that pin...