Re RTL Dongles running WSPRD this is from the WSPRD authors GITHUB account.
I think this answers my own question as I have been unable to get the blue generic Chinese RTL dongles to work with WSPRD.
“WARNING – Crystal stability
Most of RTL dongles use a cheap crystal, and frequency drift can avoid WSPR decoding. The use of no-name RTL dongle for VHF/UHF bands usually require crystal modification, for a better one. External clock could be also used, like GPSDO or rubidium reference clock, aligned on 28.8MHz. In some case, it’s possible to use the factory crystal (usually HC49, through hole), using a good thermal isolation. I successfully used two device with no modification, but it’s tricky, easy to miss the window, and RTL devices does not allows fine frequency tuning. For now, a good option is to buy a RTL device designed for SDR applications and integrating a 0.5ppm TCXO. After many tests, I would recommend this version : NooElec NESDR SMArt - Premium RTL-SDR w/ Aluminum Enclosure, 0.5PPM TCXO https://www.nooelec.com/store/nesdr-smart.html”
I have ordered a Nooelec SNArt dongle from Amazon.