Why didn't I come up with this simple upgrade to the QMX+?

This is an upgrade to the QMX+ which is so simple that I keep saying to myself: why did it take so long for someone to come up with it?

It consists only of doubling the PA transistors. The original 4 BS170s are paralleled with 4 more as shown in my implementation in the image. Very simple!

It is, as far as I understand, the brain child of Roelof PA0RDT and is described in detail on the QRPLabs website. I essentially followed those guidelines, and got more or less the same results as reported there.

There are several advantages:

• Approximately doubled output power
• More robustness to applied voltage. My QMX, wired for 9 Volts, now runs fine on 11 and more Volts, with a current limited power supply (approx. 2 Amps). 

I have had many FT8 contacts with it - where the transmitter is on continuously for 13 seconds - and have not had any problems. The only downside that I have heard of is slightly reduced power on 6 m due to the effect of the increased gate capacitance with two instead of one transistor.