And only the higher frequency radars are really useful for interception or weapons targeting. The lower frequency radars are good at long-range detection but they're far less precise.

Early stealth aircraft designs like the F-117 and B-2 were optimized for signature reduction in the frequency bands most typically used by air defense and fighter radar sets. Newer designs like the B-21 and F-47 supposedly have "broadband stealth" which reduces radar cross section across a broader range of radar bands but details are classified.