I've understood that spread-spectrum type of modulations are more resistant to narrow band jamming, for obvious reasons. What is less obvious is why someone would try to jam for example a cellular phone, GPS or ADS-B (Mode S) transmitter using a narrow-band jammer? (Whatever "narrow" or "wide" means in this context?)
What are the criteria and essential details for a jamming resistant modulation?
I have since understood quite a bit more about this topic. A wide-band jammer would spread all its energy over the entire spectrum of frequencies it tries to cover. This is extremely energy consuming and thus due to the inverse-square relation for radiation, you quickly loose energy with distance, so narrow-band beam formed jamming is preferred. However, narrow band jamming is weaker since certain frequency hopping methods can be applied to foil the jamming.