On 23/04/17 04:03, Jeff Liebermann wrote:
quote =====
When you're on the water line, antenna height does make a big
difference. Prepare a roll of coax cable setup as an RF extension
cable. Attach connectors and adapters so that they fit the radio and
the antenna. If in trouble at sea, lash the antenna to the top of a
pole or oar to gain altitude. A separate antenna, such as a common
ground plane or coax sleeve antenna at the end of the coax cable would
make a better antenna than a rubber ducky.
unquote =====

A simple alternative to the J-Pole antenna would be a ground plane
antenna made of welding rod material on an SO-239 socket with a 4 hole
square flange with a vertical quarter wave radiator and 4 hinged
radial elements,the latter under 45 degrees when in use .
The SO-239 socket would be connected to a PL-259 connector and a
suitable length of coax.

The socket + connector would be fixed into a plastic pipe ,with the coax
running inside the pipe .
The bottom of the pipe would be fixed to a simple platform the latter
clamped to the canoe.
When antenna is not in use the 4 hinged radials could be pushed in-line
with the plastic pipe mast .

It is useful to initially make the vertical radiator and radials ,say 10
mm longer than a quarter wave for the mid band frequency (somewhere
between 157 and 162 MHz).

The radiator can then be shortened (1mm at the time) to achieve lowest
SWR for the desired frequency ,using an antenna analyser or SWR meter
with the transceiver

Lastly the radials can be trimmed accordingly ,checking SWR

When all is done ,the exposed SO-239 centre pin to which the 1/4 wave
radiator is soldered (or the complete SO-239 socket can be covered with
Epoxy or Bluetack (giving excellent protection)


Frank , GM0CSZ / KN6WH in IO87AT