Ground Direction Finding

Loren and Gee

Ground Based Direction Finding [D/F] is similar to the aircraft based system but more powerful as bigger / more powerful installations were possible. The aircrew, perhaps the radio operator, held the Morse key in transmit mode for a minute while the ground operator took a bearing on the signal. If two ground stations were used, the point at which the bearings intersected produced a nav fix.

In the 1930's the onboard aircraft transmitting equipment included a 250 ft trailing aerial that was unwound after takeoff and wound in before landing. Sadly, Amelia Earhart left hers behind on the fatal flight. [Gwynn-Jones P.230]

These ground based D/F stations were still listed on pilot charts up to at least the late 1950's. The DF code in the airport's text box indicated the D/F facility.

The Marconi Adcock D/F installation as used by Pan Am at their Pacific Island bases had a range of up to 1,500 miles over the ocean. These Pan Am bases were established in 1935. [John G. Borger]

The Pan Am Pacific bases were Honolulu, Midway Is, Wake Is, Guam, Manila for the Asian route. The South Pacific route from Honolulu was Canton Is than Noumea to Auckland. [Gwynn-Jones P.224]

The Auckland Adcock base was called Musick Point after Capt Edwin Musick, the pioneering Pan Am pilot lost when the Pan Am S-42B "Samoan Clipper" disappeared January 1938. [Gwynn-Jones P.215] [Parnell / Boughton P.122]

In 1937 Australian Marconi Adcock bases were planned for; Cooktown QLD, Port Moresby PNG and Salamaua PNG. [Parnell / Boughton P.166]

1935 saw AWA establish a D/F station at Essendon Airport, Melbourne, using Bellini-Tosi equiptment. More Australian ground based D/F stations were soon built at other locations in Australia. [Job 1991. P.127]

The 1939 map of Australian D/F bases and air routes is available for viewing.  (please note this contains a 181kb gif image) [Job 1991. P.149]

In addition, radio facilities were also established at Lord Howe Island in the Tasman Sea, between Norfolk Is and Sydney. [Parnell / Boughton P.122]


Page last updated on 31/12/03

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