Thanks to @csete and many contributors, we are quite fortunate to have GPredict! Gr-gpredict-doppler from #ghostop14 Mike provides very useful OOT blocks to interface to GNUradio. Recently, while upgrading from GPredict 2.3-115 to 2.5.1, doppler correction stopped working.
Thanks to mdblack98 #Michael Black, Gpredict 2.4 and 2.5 extended the hamlib protocol significantly and added long-form backslash-prefixed commands. Mike is also the author of lots of HamLob code. Thanks Mike!
It seems that Gpredict waits for RPRT 0 after every single command before sending the next one. The very first unrecognized command, e.g.,\set_vfo_opt 1, sent immediately upon connection between updated GPredict to legacy gr-gpredict-doppler caused the connection to hang.
To address this, with Claude AI help, an updated version of doppler.py in the python folder of gr-gpredict-doppler was created.
If interested, please see GitHub - N6RFM/gr-gpredict-doppler at GPredict_2.5_support · GitHub . There is a detailed explanation of changes made to the doppler.py file in the docs folder.
Good hunting all,
Bob
N6RFM