75 Ohm Coaxial Cable Used On a 600 Ohm Output
If I searched right, the unit has a maximum output frequency of 1MHz. A 1MHz wave has 300m wavelength in free space. It will be slightly longer in a cable. So the cable you will use, will be electrically short for sure, and only the capacitive loading of the cable and thus the bandwidth is to be assessed. Such a coaxial cable should have roughly 100pF/m capacitance. 600Ω output resistance and 100pF forms a pole at 2.67MHz, so you are good* up to 1m cable length for the full range of the instrument. If you want a 1MHz frequency with a waveform including harmonics, then you should reduce your cable length, or the output impedance before the cable.
*Only 6% amplitude loss for a 1MHz sinusoid signal