I did some testing with WSPR this week to see how well my digital mode portable station performed in the field. The setup consists of a QRP transceiver and a new half-wave end-fed dipole. The s/n plots attached to this email were compiled from the WSPR data I collected when I got home.
One interesting thing revealed by the data was how the reports clustered around the same distances on both the 40 and 20 meter bands. The 40 meter band favored short NVIS distances (no surprise there) while the 20 meter band favored longer distances out to 4000 miles.
The plots also show that the bulk of my reports were below 0db which explains the limited performance of my QRP station and likely the reason why the majority of my contacts were logged while working weak-signal modes like FT8 and JS8-Call. A few CW contacts where made as well.
The exception was on 40 meters at short distances where signals were consistently high enough above the noise to make SSB contacts and certainly good enough to work any digital mode. Unfortunately, there weren't any 40 meter stations running PSK31 or any other chat modes at the time.
It was an interesting day in the field and if there's anything to be learned about digital mode portable its:
a) use an efficient multi-band antenna so you can take advantage of openings as they come and b) load a bunch of digital modes onto your portable PC so you're ready to pounce on any station that comes along.