On Sat, 22 Apr 2017 12:43:39 -0400, rickman wrote:


... 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.

Conservative radio range on VHF is:
Nautical_Miles = 1.225 * sqrt(antenna_ht_feet)
Statute_Miles = 1.415 * sqrt(antenna_ht_feet)
km = 4.124 * sqrt(antenna_ht_feet)
Mo
http://www.qsl.net/kd4sai/distance.html

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.

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.

I've also considered the possibility of a higher powered unit built into
the boat with a small remote control.

A higher power transmitter will help the Coast Guard hear you but will
do nothing for you hearing the Coast Guard. More antenna gain, and a
higher antenna are better solutions.

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.

The biggest headache with using a 25 watt radio on battery power is
that the receive current drain is rather high thanks to the display
backlighting. For example:
http://www.standardhorizon.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=83&encPr odID=1BFCB309CEE0FEE9385740D0F23313FA&DivisionID=3 &isArchived=0
0.45A very low audio
0.8A full audio
5.0A 25 w transmit
1.0A 1 w transmit
So, let's say you start off with a 12V 7A-hr SLA battery commonly
found in a UPS. You don't want to kill the battery so let's only
drain it down to 40% capacity. That would give you:
12V * 7A-hr * 0.6 = 50.4 watt-hrs
In 25 watt transmit, that give you:
50.4 watt-hrs / (12v * 5A) = 0.84 hrs * 60 min/hr
= 50.4 minutes talk time
That's actually quite a long time for a fairly small battery.

However, if you leave it running in receive, you get:
50.4 watt-hrs / (12v * 0.45A) = 6.22 hrs listen time
That's at low audio. If you wanted to hear something or transmit, it
would be much lower.

You could do better with a LiIon battery pack. The problem is that
most such packs either 3 cells, which yields about 10.8V which is
insufficient, or 4 cells, which could be as high as:
4.1v * 4 = 16.4v
which might be over the maximum voltage rating for the radio. The
Standard GX1600 is rated for 11 to 16.5V operating voltage, so you
should be ok with 4 cells.

Yep, a 25 watt radio might work.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558