On December 9, 2019 at 02:21, edmund said...
Not helpful in the least.
How do you figure? You said they know one frequency, which is 100% false. The OP may decide to go to eBay and pick up a MRF350 and end up with an "i" series because its a urc base, and according to you, will work with his mx780. He'll then be back to ask how does he get this mrf350i to work with his remote.