[Mondial]

Yes the RF cable should be terminated in 50 ohms with any generator, especially at VHF frequencies. It does not matter much at AM broacast freqs as the wavelengths are hundreds of meters long. But at 100 MHz, a wavelength is only 3 meters, and a 1/4 wavelength cable (only a few feet) which is unterminated will act as a resonant circuit causing the output to vary wildly as the freq is changed. So you really want the cable terminated in its characteristic impedance at VHF for accurate measurements.