I had previously built an 'analogue' power meter using one of the specified HP33330B diodes and a 100uA meter for a completely portable power meter that I could take out to the EME dish without worrying about mains power for the HP435 meters.
The battery-powered F1CJN meter is a step up from this, allowing for auto-ranging and offsets when using attenuator or couplers for range extension.on a nice colour LCD screen. Progress.....