Roger, quote from Warship Profiles No 4, The Graf Spee;

'The Graf Spee was the first German warship to be fitted with radar in 1938 (then known as “De Te-Great” = “Deutsches Technisches Great” = “ German Technical Equipment”). Though it could determine the range of a target, direction was, however very inaccurate. Though for this reason unsuitable for fire control, the radar was nevertheless of considerable use at night and in poor visibility. During the Spanish Civil War its effective range was increased from5 to 13 km. The aerial array, popularly known as the “Matress” among seamen on account of its shape was fitted to the revolving cupola on the foremast and coupled to the optical range-finder. A further installation, peculiar to this ship, consisted of a radio-monitoring unit that constantly swept the horizon and indicated any transmission, enabling it to be intercepted.'

So it would seem range was not a problem, just direction????