RF Sniffer / level indicator

In the last post I talked about a low power 1W amplifier that I was building for WSPR TX. This amplifier has a variable gain - a simple potentiometer at the input, nothing fancy. This will set the output level.

The Amp output will go through a 40m LPF, on to my VSWR/Power meter, then my auto ATU and small loop antenna.

Wouldn't be nice to have some indication of the level of RF output? 

So I have looked into this and have come up with a row of LEDs, four green, one yellow and one red. The idea being that if the red one is alight the amp is close to overload.

To implement this I found on eBay an Audio Sound Level Indicator . I wired this to a simple peak detector and bingo it lights up when it detects RF.

The diodes are germanium low drop.

Here's a mock up, driven from a +12V supply, RF is detected on the short yellow wire at the bottom, when my ELAD FDM-DUO is transmitting at 7W power into my loop on the window sill!!!