Radiator; Gear Box; Rf Unit; Scanner Unit - Furuno FR-1505 MARK-3 Series Service Manual

2.3 Scanner Unit

General
New cast aluminum scanner gearbox and new series of streamlined antenna are employed on the
FR-2115 and FR-2125 radars. These are not compatible with the traditional Furuno scanner
gearbox and radiator used for a long period. The mounting dimensions are remained unchanged.

Radiator

A feeder waveguide is built-in the radiator XN-12 AF, XN-20 AF and XN-24 AF for ease-
installation. The XN-20 AF and XN-24 AF are the same electrical characteristic with XN-3 A
and XN-4 A respectively.

Gear Box

The mounting dimensions, the size of the gear box, and cabling layout have not been changed
from the traditional Furuno radars. Changed is the radiator mounting bracket for a new radiator.
The gear box can be equipped with a motor of either 24 rpm or 42 rpm type.

RF Unit

The 10 kW and 25 kW RF units are the same in size. The magnetron of 25 kW is a new type,
smaller in size. The RF modulator generates short pulse 1 (S1) which has pulselength of 0.07 us
and pulse repetition rate of 3000 Hz. Traditionally, the S1 is 0.08 us and 2200 Hz.
The magnetron current monitor circuit ensures a defective magnetron being found easily. When
the magnetron is short- or open-circuited, the magnetron current detector reads 1 to 1.5 V.
2-36