QRP /P

I have an FT-817, which has seen hard use with SOTA, which I exhumed for a short break in Cornwall last week. I took a ZM-3 ATU - a manual Z match ATU, which I built a few years ago. And strung up a LW up the side of the house, with a counterpoise. The ZM tuned this quite happily, and it sounded especially perky on 30m. RX. TX was useless. Stations clearly couldn't hear me at all. Do I conclude that QRP operation running <=5W with a poor antenna is a waste of time? Or is it the ZM ATU? I use a LW at the home QTH quite successfully, and have worked VK and other DX easily with it. hmm... ZM-3 reviews
SOTA UK