Recently maintenance-free radars are strongly demanded by customers, because the use of radar has increased dramatically for ensuring safe navigation of vessels-consequently making the maintenance costs burden to replace their shorter-lived magnetrons. As if responding the customer demand, the International Maritime Organization (IMO) radar performance standard MSC 192(79) covering shipborne equipment shall come into force in July 2008; which will allow the new technology radar in the S-band frequency, in addition to the conventional pulse radars with a magnetron. In such circumstances, JRC has developed an S-band shipborne solid-state radar for the Safety Of Life At Sea (SOLAS) vessels. This radar has adopted the pulse compression method; for which we developed a several hundred-watt transmitter-receiver unit and the signal processing unit to realize the pulse compression technology. We have confirmed that our new radar achieves as sufficient performance as the conventional magnetron radars, through the field evaluation on a practical vessel.