Mk 2
Collinear with Ribbon
Cable
Slim Jim
The aerial was
made to the stated dimensions (within 1 mm). As RG213 is
thick cable,
3m of RG58 was
used to make the connection to the ribbon cable before being
connected
(BNC to N-type) to the normal RG213 downlead. [Initial tests
were
hampered by a faulty connector]
As with most Marine VHF aerials designed for mast top
mounting, the
aerial came with 18m of downlead moulded into the base of the
aerial.
This downlead was used.
How is it done ?
I'm
using a coaxial relay to
switch the aerials under control of the same PC running
Shipplotter and
plotting the graphs. It is synchronised to plot
message rate (1) or (2) on the graph as the aerial is
switched. Every
alternate message rate is
therefore recorded for a different aerial. The two aerials
are located
at the same height about 10 feet apart, using the same
type and length
of downlead and feeding the same AIS receiver (SR162).