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Mast shadow

There are no limitations on installation height as we state on each case     ' Mount the higher the better' due to the curvature of the earth. Mast shadow applies to all reflectors as the mast prohibits the interrogating radar from seeing the complete reflector. Below is a chart of mast shadow.

As there are variables if you take 22/24 degrees as a mast shadow on a typical 30ft yacht with fitted with an EM230 them you will not be far out.

Mast size length x width Centre tocentre spacing Azimuth Shadow angle Remarks
130mm x 93mm 215mm 24.40 20' - 25' Yacht
155mm x 104mm 228mm 25.70 25' - 30' Yacht
177mm x 124mm 239mm 29.10 30' - 35' Yacht
206mm x 139mm 253mm 30.70 35' - 40' Yacht
237mm x 162mm 269mm 33.50 40' - 45' Yacht
130mm x 93mm 265mm 19.90 20' - 25' Yacht
155mm x 104mm 278mm 21.20 25' - 30' Yacht
177mm x 124mm 289mm 24.20 30' - 35' Yacht
206mm x 139mm 303mm 25.80 35' - 40' Yacht
237mm x 162mm 319mm 28.50 40' - 45' Yacht

John Firth the inventor of the Echomax symmetrical array was adamant that no radar reflector should be fitted to a mast but suspended from the cross trees or halyard which virtually eliminates mast shadow and enables compensation at heel retaining virtually full response up to 20 degrees.