Who is the 500mhz version appealing to?
ISM band 433.05 MHz - 434.79 MHz
My opinion is that if do any kind of serious work there need look least 3rd harmonic.
So, for check example ISM band tx minimum is 1.5GHz spectrum.
Some smartcards run at 13.3..something mhz (the NXP MiFare RFID chips you got on the Metro in DC, MBTA in Boston and tube in London). Also, casual testing your board for EMI - e field probes for oscillators, h field probes for SPMS. It's a real ghetto ghetto way to pre-test (youre better off renting an actual high bandwidth spectrum analyzer, rather than risking having to re-design/re-run a new revision) but haha in a pinch!