that can dramatically change the reflected signal. For instance, changes in the target aircraft's direction can present different portions of the fuselage to the antenna, and dramatically change the amount of signal being returned. In these cases, a conical scan radar might interpret this change in strength as a change in position. For instance, if the aircraft were to suddenly "brighten" when it was off-axis to the left, the circuitry might interpret this as being off to the right if the change occurs when the lobe is aligned in that direction. This problem can be solved by using two simultaneous overlapping receiver beams leading to the monopulse radar, so-named because it always compares signal strength from a single pulse against itself, thereby eliminating problems with all but impossibly fast changes in signal strength. Conical-scan receive-only (COSRO) COSRO systems do not modify the transmit signal sent from the antenna. Antenna waveguide in COSRO systems includes an RF received feedhorn structure that produces a left/right RF receive sample and an up/down RF receive sample. These two signals are multiplexed inside a waveguide device that has a rotating vane. The output of the multiplex device is a single RF signal and two position signals that indicate left/right and up/down. The COSRO technique does not transmit any signals that indicate the position of the rotating vane. Antenna sampling RF receive signals from multiple transmit pulses are combined mathematically to create a vertical and horizontal signal. The vertical signal is created by adding RF samples when the vane/feedhorn is in the up direction and subtracting RF samples when the vane/feedhorn is in the down direction. The horizontal signal is created by adding RF samples when the vane/feedhorn is in the left direction and subtracting RF samples when the vane/feedhorn is in the right direction. This produces a pair of angle error signals used to drive antenna positioning drive motors. Jamming Conical scan radars can be easily jammed. If the target knows the general operating parameters of the radar, it is possible to send out a false signal timed to grow and fade in the same pattern as the radar lobe, but inverted in strength. That is, the false signal is at its strongest when the radar signal is the weakest (the lobe is on the "far side" of the antenna compared to the aircraft), and weakest when the signal is the strongest (pointed at the