My twin tuner digi-recoder has two aerial inputs and two aerial outputs, with one of the outputs connected by a special connector to one of the inputs. It only needs one aerial lead in and the output cam be connected to the tv so no splitting of the signal is neccessary.
In practise the digi-recorder is only used rarely as i mainly record off Freesat, and as a result I split the signal to go to the main tv and other sets as well as one split to the digi-recorder which is normally switched off as it is very noisy even in stand-by - hint avoid Thomson PVRs.