I have the preliminary results. I can now confirm - when the red LED is lit it does indeed mean the board is working properly! All kidding aside, as bd139 said, it does look like the AD8310 part works well.
Here's the initial data.
First to calculate dBm you need to measure Vo and use a simple equation to get power. I rearranged the equation they had in the datasheet which was using their scale of dBV, added a correction to give answers in dBm, and came up with this:
Pin (dBm) = (Vo - 2.28) / .024
I made an initial power measurement using the known accurate output power of the hp 437b power meter reference (0.0 dBm, 1 mW @ 50 MHz).
I measured a Vo of 2.295 V which results in a calculated input power of 0.625 dBm. I then set my Agilent 8648A to the same settings (50 MHz, 0.0 dBm) and connected the board to the Agilent. I did another measurement with the board and I got the exact same answer. So the error at that point is 0.625 dBm. This shows using the 8648A is good to go forward.
I then proceeded to check other data points @ 50 MHz as follows:
-80, -40, -20, +10 (dBm).
Here are all the results:
-80 dBm
Vo = 0.371, calculated input power = -79.5 dBm [error 0.5 dBm]
-40 dBm
Vo = 1.316, calculated input power = -40.08 dBm [error -0.08 dBm]
-20 dBm
Vo = 1.87, calculated input power = -19.6 dBm [error 0.4 dBm]
0 dBm
Vo = 2.295, calculated input power = 0.625 dBm [error 0.625 dBm]
+10 dBm
Vo = 2.54, calculated input power = +10.8 dBm [error 0.8 dBm]
Instruments used: hp 437 power meter, Agilent 8648A RF signal generator, hp 34401A DMM
Note: The stated power output accuracy of the Agilent 8648A is +/- 1 dB
Initial Conclusions
It works well, better than I thought it would. I don't see any reason why you couldn't design a useful power meter for hobbyist use around the AD8310. I don't think I made any mistakes. I never have before ... well I thought I did once before, but I was wrong about that time.
Next I want to make a set of graphs to better check the performance at different frequencies, which I'll work on in the next few days.
After that, I want to toss in a microcontroller with display to get real-time measurements properly displayed as dBm and watts. With a clock ... no, no clock I have too many clocks even my soldering station has a damn clock.