mcHF Kit, issue with RF where it shouldn't be.

[TheBay]

I recently built a mcHF kit, but having an issue with a distorted output,
basically what is happening is RF is getting through the Tx/Rx section and on to the Bias circuit for the Rx pin diode 
so RF is getting all the way up to U7 which is a 74 series logic IC, it's either causing issues with neighbouring IC's through close
tracks or directly from U7. I can see this RF with a RF probe or a spectrum analyser.

RF is supposed to be blocked by a 47uh inductor labeled RFC2, if I remove either C78 or RFC2 from the circuit the issue has gone, but obviously I have no Rx!
checking that path with the RF probe or SA there is no evidence of RF getting back so it's definitely getting in through RFC2.

I've tried resistors inline or on top of the inductor and can remove the RF at some frequencies but it still appears on other bands.

I have spoken to other owners some have it some claim they don't but having changed every component in that section and it remains I just think some don't notice it personally.
It's unusable for me on JT65 as it's outputting awful distortion and causing a lot of spurious signals when using phone modes.

Attached is a screenshot of the schematic and some screenshots of my SDR with and without the noise/distortion/oscillation.
The link to the schematics are here:
http://www.m0nka.co.uk/wp-content/uploads/2016/03/mcHF_rf.pdf

[DimitriP]

Have you tried bodging  100nF on U7 p3 to p7 and p1 to P7?

[TheBay]

Have you tried bodging  100nF on U7 p3 to p7 and p1 to P7?

I've tried another 100nF on R54 and also on Pin 2 of U7, I'm getting around -8v on R54 when I Tx but only -0.85 on the other side of R54
If I remove R54, RFC2 or C78 the problem has gone.

Really puzzled with this.

[CJay]

Remove the drive through the PA/LPF and check the DC conditions on the PIN diodes to make sure you have the correct TX/RX switching happening.