CHIRP

What does the radio do if you put 136.0MHz in the VFO? CHIRP cannot control whether this radio is in AM or FM, because the radio chooses itself by the frequency. When this has come up in the past, a user confirmed that 136.0MHz was regarded as "FM" by the radio this driver is based on, and one step down from that was regarded as "AM". If you report differently for this model, then CHIRP can be updated to mirror the radio's behavior, but it cannot allow you to choose AM or FM along lines not chosen by the radio itself. If you want to do that, you need to buy a higher-quality radio.

Nearly every Chinese radio that I have dealt with the frequency range of a band is >= low limit but < high limit. The radio doesn't give you a choice of which mode to choose (AM or FM). The selection is automatic based on selected frequency. In other words only the frequencies from 108 MHz to current STEP size below 136 MHz will automatically be AM. 136 MHz and up would automatically be FM (or NFM). Neither the user or CHIRP can change that.

Copy that. It is indeed a radio limitation then.