I’ve done some basic testing using the RF modulator in an old Philips VCR (VR 710) fed with composite video from a PS2, outputting PAL-G. The VCR was connected to the expansion board over a 2.5 meter (8 ft) cable with F plugs and an F to Belling-Lee adapter on the VCR end. The tests were made at a few frequencies in the range of 500-600 MHz with default and custom comb filtering settings.
I’m very happy with the picture over RF in this case. There was no visible interference with the above setup. Unfortunately the VCR I used has a problem with its audio input, so I couldn’t test sound demodulation there.
With a less well shielded cable, a weaker and/or worse quality signal (RF modulators in home computers and consoles tend to be worse than those in VCRs) and at other frequencies there may be issues, but I haven’t been able to test that so far.