[Paleo Conservative]

Passive radars are not vulnerable to HARM missile attack, since they do not emit any signal. They monitor existing VHF/UHF TV transmissions and cell-phone tower transmissions. A stealth aircraft may absorb radar directed towards it, but it will cast a "shadow" if it flies between a TV tower and a passive radar station.

If you target the electrical power generating and distribution systems, there won't be enough power available to run cell phone towers and TV stations.

[steveegg]

That'll work too. I'm sure that there's a couple of other tricks up the USAF's sleeve.

[Mad_Tom_Rackham]

If you target the electrical power generating and distribution systems, there won't be enough power available to run cell phone towers and TV stations.

Weapons systems will have backup power (local generators, etc.).

[Darksheare]

An EMP would work. And it wouldn't even be nuclear to start with. We developed an EMP a couple years back, has energised copper coils inside it packed around a couple HE charges. When the HE goes, the coils collapse and an EMP pulse is produced. (VERY brief and as undescriptive as possible. Don't want to be helpful to anyone other than us.)

A passive radar would be just as sensitive to an EMP pulse as any other electronic system. Not to mention, the local power grid would suffer dramatically.