The basic theory of a jamming system is that when the target receiver(handset devices, walkie talkie, IED, drone, etc.) receives an "effective interference signal" more than the "original signal" 6dB to 20dB in the target channel and location, at this time, target receiver can be jammed.
The following is a general estimating formula for signal level from Jammer.
Rg=10lg [Pg/(Wg/Ch)] +Ag – Lg (1)
Lg=32.4+lg(FD) + Lf (2)
Rg: The received output power from Jammer unit to target channel (dBm)
Pg: The full output power of Jammer (W)
Wg: The bandwidth of jamming band (MHz)
Ch: The channel bandwidth of jamming target (MHz)
Ag: The comprehensive gain of antenna (dB), including the gain of the antenna and the loss from the cable.
Lg: The path loss between antenna and jamming target (dB)
F: Center Frequency (MHz); i.e.: 1842.5MHz of 1805-1880MHz
D: Distance between antenna and jamming target (km)
Lf: The frequency compensation from the loss (for example, the Lf of the DCS system is 6dB)
100W DCS jammer for instance:
The frequency range of the DCS system from 1805 to 1880MHz with 0.2MHz channel width and 100 watts output power. When the comprehensive gain of an antenna is 0dB, Theoretically, the "effective interference signal" to 100 meters jamming distance should be:
The jamming coverage diagram can refer to The Jammer Coverage Model