tens of meters, but this is independent of range. This means SARH missiles can have much smaller warheads with the same overall effectiveness, although at the cost of having additional electronics on the missile. The downside to the SARH approach is that the signal provided by the ground radar has to contain some form of additional encoding of the signal for the missile to determine the direction of the target within the cone-shaped signal it sees. Normally this is accomplished using a form of conical scanning which uses the timing of variations in the signal to determine the angle within the cone, but this demands that the signal is continuous, or "locked on". This is normally accomplished with SAMs by using a separate target illumination radar dedicated to this task. In both cases, SAMs required separate radars for each missile being guided, which means that the system as a whole can only guide the number of missiles that it has radars. For SAMs in high-traffic environments, especially ships facing salvos of anti-shipping missiles, it is possible to overwhelm the system's capabilities. In theory, the missile can add electronics to allow it to continue tracking a non-continuous signal and thus allow a single radar to provide tracking to several missiles, but using electronics of the 1950s and 60s this would be prohibitively expensive and large; even command guided systems generally lacked this capability. Addressing this was a major concern, especially for the US Navy and Royal Navy. Track-via-missile combines these two concepts to avoid the problems of both. Like SARH, the receiver is placed on the missile and thus has increased accuracy as it approaches the target. Instead of processing it locally, the signal is instead rebroadcast on another frequency and received by the launcher. The launcher then compares the signal it sent to the one received by the missile, and through this comparison can perform the determination of the target location relative to the missile. But because the ground station knows the rough location of the target, and details of the original signal it sent, it does not require the signal to be continual and thus does not demand a separate illumination radar. After comparison and calculation, updates are sent to the missile as in the command-guided case using a data link. TVM solves the accuracy problem of command guidance, but not the issue of requiring separate radars. In theory,