Richard
The display will read out the frequency well beyond the limits of the chip to produce a signal at that reading. I checked mine and at about 100 MHz and the voltage of the signal starts to go down. At about 200 MHz it is very weak and somewhere above that no signal. I would say from those rudimentary facts the VFO is practical to use from about 3MHz to about 100MHz with out additional circuitry to boost the signal. Most of us are interested in the HF spectrum anyway and if you were interested in VHF or UHF frequencies there are other methods to get to those bands.
Bill N7EU
