The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

crackling sound. What they were hearing was high-frequency static, but
because they had already discounted high frequency for radar – they were
using very-high-frequency (VHF) and ultra-high-frequency (UHF) ranges –
it did not occur to them that they were in fact picking up beams from a
radar network.
The Zeppelin had been picked up immediately by one CH station after
another, its course plotted and tracked carefully. Going into cloud, it
actually drifted over Hull, well into British airspace, but despite the
temptation to send a radio signal telling them so, those charting its
movement decided to keep shtum. Soon after, the Zeppelin turned for home,
with General Martini none the wiser. Convinced there must have been some
kind of technical defect with the airship’s own kit, Martini sent it over
again. In August, in bad weather, the Zeppelin came over a second time.
This time, however, it picked up nothing at all, not even static. By sheer
fluke, the radar chain had been turned off that day to sort out some minor
malfunction.
Less than a month later, war broke out and any further investigations
into the strange high towers dotted along the British coast were put on hold.
This did not unduly concern Martini, however, or any of the Luftwaffe High
Command. Because of their size, shape and use of high frequency, the
masts had been discounted as being radar. Unwittingly, the crude, rather
ungainly appearance of these monster masts had worked very much in
Britain’s favour.
Just to put the seal on it, they discovered a British mobile radar set that
had been abandoned near Boulogne. Although rather like the German
‘Freya’, this was even more rudimentary. Instead of being impressed by
their find, the Germans who examined it were delighted to discover the
British had such crude pieces of kit and were operating a DeTe set so
technologically behind their own.
Now, as they looked across the Channel to the high masts perched
above the white cliffs of Dover, they still had no clear idea what these
pylons were for. Soon enough, though, once they were over England, they
would find out.