But in this case passive radar would help enormously? It could detect the aircraft and help to launch an IR missile, effectively rendering the stealth capabilit

But in this case passive radar would help enormously? It could detect the aircraft and help to launch an IR missile, effectively rendering the stealth capabilities useless. Deployed at borders, it could provide good air defense against F35. You obviously need strong signals for passive radar to work but those could be positioned inland and they don't need to be where the passive radar is, making it harder to disable it.