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

On Sat, 22 Apr 2017 20:03:49 -0700, Jeff Liebermann
wrote:


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)

Something is wrong with the km line above. Perhaps the antenna height
should be in meters? Or, the constant should be 2.278.

On Sun, 23 Apr 2017 07:10:17 -0400, Pat wrote:

On Sat, 22 Apr 2017 20:03:49 -0700, Jeff Liebermann
wrote:


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)

Something is wrong with the km line above. Perhaps the antenna height
should be in meters? Or, the constant should be 2.278.

Oops and thanks. That should be:

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

In article ,
says...

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


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.


Going from 5 to 25 watts of FM will gain almost nothing. Raising the
antenna several feet from the sitting down position will gain a lot.

On 4/23/2017 10:17 AM, Ralph Mowery wrote:
In article ,
says...

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


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.


Going from 5 to 25 watts of FM will gain almost nothing. Raising the
antenna several feet from the sitting down position will gain a lot.

Are you saying that a hand held 5 watt transceiver with a rubber ducky
antenna will reach all receivers because of the line of sight
limitation? Is that true even for contacting a land station with a 200
foot high antenna? A 3 foot high antenna and a 200 foot high antenna
give nearly 20 statute miles of range. Will 5 watts be heard that far
away?

--

Rick C

On 4/23/2017 12:00 PM, rickman wrote:
On 4/23/2017 10:17 AM, Ralph Mowery wrote:
In article ,
says...

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


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.


Going from 5 to 25 watts of FM will gain almost nothing. Raising the
antenna several feet from the sitting down position will gain a lot.

Are you saying that a hand held 5 watt transceiver with a rubber ducky
antenna will reach all receivers because of the line of sight
limitation? Is that true even for contacting a land station with a 200
foot high antenna? A 3 foot high antenna and a 200 foot high antenna
give nearly 20 statute miles of range. Will 5 watts be heard that far
away?

Opps, make that nearly 20 nautical miles. It's over 22 statute miles.

--

Rick C

rickman wrote:
On 4/23/2017 10:17 AM, Ralph Mowery wrote:
In article ,
says...

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


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.


Going from 5 to 25 watts of FM will gain almost nothing. Raising the
antenna several feet from the sitting down position will gain a lot.

Are you saying that a hand held 5 watt transceiver with a rubber ducky
antenna will reach all receivers because of the line of sight
limitation? Is that true even for contacting a land station with a 200
foot high antenna? A 3 foot high antenna and a 200 foot high antenna
give nearly 20 statute miles of range. Will 5 watts be heard that far
away?

Radio amateurs have launched satellites which usually have about 1 to 5 W
of power on VHF and UHF. Those can be clearly heard on a portable
with a very small antenna even when 2000-3000km away.

The loss of signal on line of sight is easy to overcome with narrow
band modulation and this kind of power. It is the "beyond line of sight"
attennuation that is the problem. Everything you can do to remove that
will help a lot more than power.

Today I was working at the repeater in our local radio/tv tower. We
were at 220m above ground level and it was easy to work over a repeater
about 80km away from us using only a handy with 1W of output. Only
because at that height this is (almost) line of sight.

In article , rickman
wrote:

A 3 foot high antenna and a 200 foot high antenna
give nearly 20 statute miles of range. Will 5 watts be heard that far
away?

Rick-

I have not done the calculations, but think your limit is line-of-sight
rather than power. I once talked 50 miles to an aircraft on Two Meters,
using a 1 watt handheld with rubber ducky antenna.

This assumes the Coast Guard does not have their squelch set too tight.

Fred

On Sun, 23 Apr 2017 12:00:09 -0400, rickman wrote:

Will 5 watts be heard that far away?

Let's see what the Fiis equation says, assuming line of sight, perfect
conditions, and no obstructions:
http://www.proxim.com/products/knowledge-center/calculations/calculations-system-operating-margin-som

Distance = 20 statute miles
Operating frequency is about 156MHz
Rubber ducky antenna gain is about -3dB
Coax cable loss is zero.
5 watts tx power is +37dBm
25 watts tx power is +44dBm
Rx sensitivity is 0.18uV = -122dBm/12dB SINAD

Plugging into the above calculator, I get for 5 watts:
106.5 dB path loss
-75.5 dbm rx signal strength
46.5 dB fade margin

In other words, with this arrangement, your receive signal is 46.5dB
stronger than the minimum level (12dB SINAD) necessary to hear a
fairly weak and noisy signal. You should theoretically have no
problems being heard at 20 miles.

However, that's theory, not practice. At 156 MHz, the Fresnel zone is
rather large. Quite a bit of signal is lost bouncing off the water
surface, or being absorbed. There are waves that get in the way. The
curvature of the earth raises the wave height at mid span, resulting
in more blockage. My experience is about 5 miles maximum for reliable
communications between two handhelds over water. Icom sorta suggests
3 to 8 miles:
https://www.westmarine.com/WestAdvisor/Selecting-a-VHF-Handheld-Radio
Please read the "What are the limits of range and power?" near the
bottom of the page.

Propagation over water is also full of oddities and anomalies:
"The propagation of VHF and UHF radio waves over sea paths "
https://pdfs.semanticscholar.org/a6ca/1fe1ca92e96a7e7150217b265816891b102e.pdf
I've been in situations where I can see the person or station that I'm
trying to communicate but because of inversion layers and surface
reflections, the signal was weak, variable, or gone.

You mentioned that it's not over salt water. In that case, land
topography has a huge effect on propagation. If your friend is in a
river canyon, raising the antenna a few feet isn't going to do
anything useful. For such situations, land the kayak, climb the walls
of the canyon, and try the radio where there's fewer obstacles.


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

On 4/23/2017 2:31 PM, Jeff Liebermann wrote:
On Sun, 23 Apr 2017 12:00:09 -0400, rickman wrote:

Will 5 watts be heard that far away?

Let's see what the Fiis equation says, assuming line of sight, perfect
conditions, and no obstructions:
http://www.proxim.com/products/knowledge-center/calculations/calculations-system-operating-margin-som

Distance = 20 statute miles
Operating frequency is about 156MHz
Rubber ducky antenna gain is about -3dB
Coax cable loss is zero.
5 watts tx power is +37dBm
25 watts tx power is +44dBm
Rx sensitivity is 0.18uV = -122dBm/12dB SINAD

Plugging into the above calculator, I get for 5 watts:
106.5 dB path loss
-75.5 dbm rx signal strength
46.5 dB fade margin

In other words, with this arrangement, your receive signal is 46.5dB
stronger than the minimum level (12dB SINAD) necessary to hear a
fairly weak and noisy signal. You should theoretically have no
problems being heard at 20 miles.

However, that's theory, not practice. At 156 MHz, the Fresnel zone is
rather large. Quite a bit of signal is lost bouncing off the water
surface, or being absorbed. There are waves that get in the way. The
curvature of the earth raises the wave height at mid span, resulting
in more blockage. My experience is about 5 miles maximum for reliable
communications between two handhelds over water. Icom sorta suggests
3 to 8 miles:
https://www.westmarine.com/WestAdvisor/Selecting-a-VHF-Handheld-Radio
Please read the "What are the limits of range and power?" near the
bottom of the page.

Propagation over water is also full of oddities and anomalies:
"The propagation of VHF and UHF radio waves over sea paths "
https://pdfs.semanticscholar.org/a6ca/1fe1ca92e96a7e7150217b265816891b102e.pdf
I've been in situations where I can see the person or station that I'm
trying to communicate but because of inversion layers and surface
reflections, the signal was weak, variable, or gone.

You mentioned that it's not over salt water. In that case, land
topography has a huge effect on propagation. If your friend is in a
river canyon, raising the antenna a few feet isn't going to do
anything useful. For such situations, land the kayak, climb the walls
of the canyon, and try the radio where there's fewer obstacles.

I said the particular case I was being asked about was not over salt
water. I didn't say it was on a river. The particular case is for use
on the Great Lakes. Other uses I might have at other times would likely
be on salt water such as the Chesapeake Bay and tributaries or the
Atlantic ocean.

Your info is helpful. Thanks.

--

Rick C