Occurred now with two OMs of a similar constellation: PTT configured by DTR/RTS. Selected as VARA modem type: VaraHF, selected for the QO100 varasat.exe. In the settings we can try PTT and the transmitter is also keyed. However, no PTT is switched in the working window. If select "VaraFM" as the VARA modem type, then the PTT is switched. Shouldn't it also work with VaraHF? Settings like this 73 Thomas DL5BCA