Hulsmeyer's work led to intermittent German research only, but in March 1934, before Watson-Watt had even started, Rudolf Kuhnold head of German Navy Research, prompted by the sucess of sonar, obtained a radar reflection from a battleship across Kiel harbour. Six months later he could detect a ship at seven miles distance. This led to the pocket battleship Admiral Graf Spee being equipped with a gun ranging radar known as Seetakt during a refit in 1938. During the earlier experiments it was observed that aircraft caused disturbance when flying through the beam : this was not ignored and two years later, Freya (on the right) was able to detect an aircraft at over fifty miles although not its height. Also Wurzburg was demonstarated as an ack-ack radar with a range of eighteen miles, later to be improved to an accuracy of half a degree and 100 metres. So rather than smugly thinking that we were well ahead with our radar, it may come as a surprise to know that the Germans were thus in some ways more technically advanced than the British by 1940, although their permanent installations numbered only eight and these were confined to the German coastline. The British most certainly did not invent radar, only a version of it. But we did invent the cavity magnetron!

Freya was a metric rotating search radar with a range of 125 miles. It operated on a 2.5 metre wavelength with a power of 125 Kw. PRF was 500 and pulse length 3 microseconds. It had "bed spring" dipole array aerials, the one for receiving being mounted above the transmitter array and the whole thing was originally designed to be trailer mounted. A variant is the model depicted above on the right which has a lower third array with fewer dipoles, perhaps for IFF? During the first winter of the war Freya radars on the German islands caused severe losses to our bomber formations and in May 1940 at Essen-Frintrop a flak battery shot down a bomber that they could not see visually.

Wurzburg had a 3 metre diameter dish and operated on a .5 metre wavelength using a very high PRF of 3750 and a magnetron (not a cavity magnetron) delivered 6 Kw, giving a range of 6 miles when used as an Ack Ack radar. Obviously the problem of Transmit/Receive switching had been solved as there is only one dish for both purposes. A later similar but better version was known as Mannheim.

A larger Giant Wurzburg was developed with a 24 foot skeleton dish.

This version had a 50 mile range due to the more efficient dish with the PRF reduced to 1875 to suit. This radar could be mounted on a railway wagon for mobility.

Overall the German radar system was inferior to ours in that each unit operated independently - they had no central control rooms to amalgamate the information from many units. At that time, lacking the PPI display, the view for the Controller was provided by blobs of light on a vertical cinema type screen which had on it an outline map with a grid : the blobs came from several hand-held devices the operators of which presumably received a stream of updating reports from the radar operators who were using A scan CRT displays. The permanent installations evolved to consist of one Freya and two Giant Wurzburgs. These controlled interceptions only within a surrounding forty kilometre (approx.) square "cell". General Kammhuber oversaw the building of the Himmelbett line of these installations across Germany. The Freya detected a target at long range and handed its range and bearing to a daughter Wurzburg. When the Wurzburg could track it the other Wurzburg tracked and guided a defending fighter from a squadron associated with the radar installation to the target. An installation would not deal with an attacker outside its own cell, although overlap must have occurred during active interceptions of an evasive enemy.

Jagdschloss was another machine for tracking bomber formations at long range. This rotating device of I50 kW had 18 dipoles and the operator had the benefit of a PPI display. Pulse length was 1 microsecond and the PRF was 500.

The Germans also developed an unlikely- to- be- jammed passive radar known as Klein-Heidelberg. This picked up the CH transmitted pulses and the omnidirectional reradiated returns. Presumably at least two such stations would be needed to determine target bearing.

The Mamut (Mammoth) was a huge fixed array, 98 feet wide and 30 metres high, with no less than 192 dipoles which could be fired in groups allowing a variety of angles up to a hundred degrees to the beam produced. It was equivalent to 16 Freyas and had 200kW of power giving a 200 mile range (but no heights). Known as "The Hoarding" to allied pilots it was the forerunner of the modern "phased array". At some sites two worked back to back.

Acknowledgements
The first three pictures were sourced from Wikipedia links under Freya & Wurzburg, the source sites having larger pictures some of which are in colour, and the last two were found in a most informative site Vectorsite, to which you should now go if you need to know a whole lot more about German radar.