On 4/22/2017 12:25 PM, Fred McKenzie wrote:
In article , rickman
wrote:

Can you explain what would be preferable about the J-pole antenna? One
big disadvantage is that it appears to be more like 6 foot long for 2
meter use. That could be rather heavy and clumsy on a kayak.

Rick-

You are correct about the size. On the other hand, any separate antenna
for the VHF Marine band will be a bit clumsy on a kayak.

The "J" end of a J-pole is used to match a cable to the high impedance
of the end of a half wave element. One advantage of a vertical half
wave entenna is that it directs more energy towards the horizon,
compared to a quarter wave ground plane antenna.

Jeff Liebermann's analysis sounds like the best approach to VHF on a
kayak. But no matter which way you go, you are transmitting from a
point close to the water. You are limited to line-of-sight to another
kayak. Range to a base station will be mostly determined by the height
of the base station antenna.

That is an issue I have already explored. There is not much hard
information available, but it would appear that the rubber ducky antenna
is adequate for use from one kayak to another for the most part. BTW,
that range is twice the distance to the horizon which is about two
nautical miles.

Communications to a land station such as the Coast Guard would be much
longer given the height of their antennas, unless your transmitted power
level is too low to reach them. You might be able to receive their
transmissions which are at a higher power, but they might not be able to
hear your transmissions. In that case a better antenna might make the
difference between rescue and not.

I've also considered the possibility of a higher powered unit built into
the boat with a small remote control. A cordless remote would be the
best option I believe and I expect they are available. A power boost
from 5W to 25W would easily beat the performance of a larger antenna.
Not sure how much this would weigh with a battery, but I don't think the
battery would need to be so large. It's not like 25W has to be used for
every transmission.

--

Rick C