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

On Sun, 23 Apr 2017 15:16:40 -0400, rickman wrote:

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.

It's my understanding the propagation over the Great Lakes is similar
to that over the ocean. However, I have no experience on the Great
Lakes.

Your info is helpful. Thanks.

Y're welcome. I mentioned the problem to a friend who was into
kayaking when he was younger. He said that kayaks often carry push
poles to get them off the rocks. These are often used as an
improvised distress flag mast. I found this one:
https://thesuperstick.com/product/push-pole/
which goes to 17ft extended. Hopefully, there are cheaper models.

To attach an antenna, there's the usual roll of coax cable and some
kind of temporary mounting clip. Perhaps something like this, but
with lower loss coax cable:
http://www.dhgate.com/product/nagoya-rb-clp-window-clip-mount-rg-174-u/176624090.html
https://www.aliexpress.com/store/product/NAGOYA-RB-CLP-Window-Clip-Mount-RG-174-U-3m-Cable-BNC-for-walkie-talkie-Radio/1295452_32312249435.html
Or, just an L-bracket with a connector attached. Or, a big rubber
band. Whatever gets the antenna higher.

You're on your own on how to keep the push pole mast upright.

Vessels sometimes carry "emergency" antennas. The idea is that if the
main antenna is in some way lost, the emergency antenna would be
substituted. Examples:
https://www.westmarine.com/buy/shakespeare--stowaway-emergency-vhf-antenna--519058
http://shakespeare-ce.com/marine/product/sl-156-emergency-vhf-antenna/
They're usually small and have little gain, but might offer some
useful ideas.

Lunch beckons...
--
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 4:26 PM, Jeff Liebermann wrote:
On Sun, 23 Apr 2017 15:16:40 -0400, rickman wrote:

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.

It's my understanding the propagation over the Great Lakes is similar
to that over the ocean. However, I have no experience on the Great
Lakes.

I believe the issue of salt water came up because of a materials
concern, aluminum vs. stainless steel.


Your info is helpful. Thanks.

Y're welcome. I mentioned the problem to a friend who was into
kayaking when he was younger. He said that kayaks often carry push
poles to get them off the rocks. These are often used as an
improvised distress flag mast. I found this one:
https://thesuperstick.com/product/push-pole/
which goes to 17ft extended. Hopefully, there are cheaper models.

Not sure who told you about "push poles", but I've never run into
kayaker with a push pole. If you get on rocks, you have a paddle. I
don't even know where you would stow a push ploe. Much better to not
get on the rocks.


To attach an antenna, there's the usual roll of coax cable and some
kind of temporary mounting clip. Perhaps something like this, but
with lower loss coax cable:
http://www.dhgate.com/product/nagoya-rb-clp-window-clip-mount-rg-174-u/176624090.html
https://www.aliexpress.com/store/product/NAGOYA-RB-CLP-Window-Clip-Mount-RG-174-U-3m-Cable-BNC-for-walkie-talkie-Radio/1295452_32312249435.html
Or, just an L-bracket with a connector attached. Or, a big rubber
band. Whatever gets the antenna higher.

You're on your own on how to keep the push pole mast upright.

Vessels sometimes carry "emergency" antennas. The idea is that if the
main antenna is in some way lost, the emergency antenna would be
substituted. Examples:
https://www.westmarine.com/buy/shakespeare--stowaway-emergency-vhf-antenna--519058
http://shakespeare-ce.com/marine/product/sl-156-emergency-vhf-antenna/
They're usually small and have little gain, but might offer some
useful ideas.

If I find a kayak with a roll down window I'll get one of these and try it.

A kayak is not a large fishing vessel. It is a small, narrow boat with
little deck space. I had a deck mounted light on a two foot pole and it
was always a problem by being in the way, especially when getting in and
out of the boat. You wouldn't believe how stupid and crappy many
kayaking products are.

I seriously doubt any sort of deck mounted antenna will be acceptable to
a serious kayaker, but if it is unobtrusive and light enough it might
work. There are a number of commercial marine VHF antennas that should
do the job. The trick will be finding one that works as well on a kayak
deck as a power boat. That's the main reason why kayakers use hand held
radios.

--

Rick C

On Sun, 23 Apr 2017, rickman wrote:

On 4/23/2017 4:26 PM, Jeff Liebermann wrote:
On Sun, 23 Apr 2017 15:16:40 -0400, rickman wrote:

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.

It's my understanding the propagation over the Great Lakes is similar
to that over the ocean. However, I have no experience on the Great
Lakes.

I believe the issue of salt water came up because of a materials concern,
aluminum vs. stainless steel.


Your info is helpful. Thanks.

Y're welcome. I mentioned the problem to a friend who was into
kayaking when he was younger. He said that kayaks often carry push
poles to get them off the rocks. These are often used as an
improvised distress flag mast. I found this one:
https://thesuperstick.com/product/push-pole/
which goes to 17ft extended. Hopefully, there are cheaper models.

Not sure who told you about "push poles", but I've never run into kayaker
with a push pole. If you get on rocks, you have a paddle. I don't even know
where you would stow a push ploe. Much better to not get on the rocks.


YOu have the length of the kayak. A bamboo pole is light, and making an
antenna out of wire won't burden the pole. The real issue, I'd say, is
figuring out something to put on the kayak to hold the pole. For
emergencies, you can probably just have some fishing line tied to the top
of the pole, and hold that as a "guy wire".

If there was some way to hold the oar against the kayak, some clip on
antenna that used the oar as a mast would be better than nothing, and of
course doesn't require an extra pole.

A bit of height probably does make an improvement, after that the "mast"
has to get higher and higher to be useful.

Michael

On 4/24/2017 3:44 PM, Michael Black wrote:
On Sun, 23 Apr 2017, rickman wrote:

On 4/23/2017 4:26 PM, Jeff Liebermann wrote:
On Sun, 23 Apr 2017 15:16:40 -0400, rickman wrote:

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.

It's my understanding the propagation over the Great Lakes is similar
to that over the ocean. However, I have no experience on the Great
Lakes.

I believe the issue of salt water came up because of a materials
concern, aluminum vs. stainless steel.


Your info is helpful. Thanks.

Y're welcome. I mentioned the problem to a friend who was into
kayaking when he was younger. He said that kayaks often carry push
poles to get them off the rocks. These are often used as an
improvised distress flag mast. I found this one:
https://thesuperstick.com/product/push-pole/
which goes to 17ft extended. Hopefully, there are cheaper models.

Not sure who told you about "push poles", but I've never run into
kayaker with a push pole. If you get on rocks, you have a paddle. I
don't even know where you would stow a push ploe. Much better to not
get on the rocks.


YOu have the length of the kayak. A bamboo pole is light, and making an
antenna out of wire won't burden the pole. The real issue, I'd say, is
figuring out something to put on the kayak to hold the pole. For
emergencies, you can probably just have some fishing line tied to the
top of the pole, and hold that as a "guy wire".

If there was some way to hold the oar against the kayak, some clip on
antenna that used the oar as a mast would be better than nothing, and of
course doesn't require an extra pole.

A bit of height probably does make an improvement, after that the "mast"
has to get higher and higher to be useful.

Bamboo poles are not all that light and they get water logged.
Everything on a kayak gets wet.

So far I haven't found anything definitive that even shows a better
antenna is needed. It would appear if you are trying to contact a
station with a high antenna some 20 miles away you might have trouble
with range, but the problem isn't that your antenna isn't high enough.
Reaching other handheld units is limited by line of sight which would be
helped by a higher antenna. I'm not sure which problem was being
addressed. Next time I talk to my buddy I'll ask more about this. I
think in reality this was prompted by someone recommending a home brew
antenna when the nature of the problem wasn't even explored.

--

Rick C

On Mon, 24 Apr 2017, rickman wrote:

On 4/24/2017 3:44 PM, Michael Black wrote:
On Sun, 23 Apr 2017, rickman wrote:

On 4/23/2017 4:26 PM, Jeff Liebermann wrote:
On Sun, 23 Apr 2017 15:16:40 -0400, rickman wrote:

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.

It's my understanding the propagation over the Great Lakes is similar
to that over the ocean. However, I have no experience on the Great
Lakes.

I believe the issue of salt water came up because of a materials
concern, aluminum vs. stainless steel.


Your info is helpful. Thanks.

Y're welcome. I mentioned the problem to a friend who was into
kayaking when he was younger. He said that kayaks often carry push
poles to get them off the rocks. These are often used as an
improvised distress flag mast. I found this one:
https://thesuperstick.com/product/push-pole/
which goes to 17ft extended. Hopefully, there are cheaper models.

Not sure who told you about "push poles", but I've never run into
kayaker with a push pole. If you get on rocks, you have a paddle. I
don't even know where you would stow a push ploe. Much better to not
get on the rocks.


YOu have the length of the kayak. A bamboo pole is light, and making an
antenna out of wire won't burden the pole. The real issue, I'd say, is
figuring out something to put on the kayak to hold the pole. For
emergencies, you can probably just have some fishing line tied to the
top of the pole, and hold that as a "guy wire".

If there was some way to hold the oar against the kayak, some clip on
antenna that used the oar as a mast would be better than nothing, and of
course doesn't require an extra pole.

A bit of height probably does make an improvement, after that the "mast"
has to get higher and higher to be useful.

Bamboo poles are not all that light and they get water logged. Everything on
a kayak gets wet.

I was thinking of the bamboo stakes sold for tying plants to. Those are
thin, but so long as the antenna is made of wire, and thus light, would
work fine.

I've used the stakes, because they were handy, to get a TV loop up a bit
higher to scan the channels on the tv set.

But I wasn't thinking of the water, and you're right, they wouldn't hold
up after being kept wet a few times.

How about fibreglass? Those flags seen on bicycles to give some height
for oncoming vehicles, one of those might do. Or I have a vague memory of
seeing such things sold for kayaks, to be seen a bit sooner than when a
bigger boat stumbles on them. If they have them for kayaks, that's a good
route to take, they would come with something to use to mount on the
kayak.

Michael

On 4/25/2017 1:46 PM, Michael Black wrote:
On Mon, 24 Apr 2017, rickman wrote:

On 4/24/2017 3:44 PM, Michael Black wrote:
On Sun, 23 Apr 2017, rickman wrote:

On 4/23/2017 4:26 PM, Jeff Liebermann wrote:
On Sun, 23 Apr 2017 15:16:40 -0400, rickman wrote:

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.

It's my understanding the propagation over the Great Lakes is similar
to that over the ocean. However, I have no experience on the Great
Lakes.

I believe the issue of salt water came up because of a materials
concern, aluminum vs. stainless steel.


Your info is helpful. Thanks.

Y're welcome. I mentioned the problem to a friend who was into
kayaking when he was younger. He said that kayaks often carry push
poles to get them off the rocks. These are often used as an
improvised distress flag mast. I found this one:
https://thesuperstick.com/product/push-pole/
which goes to 17ft extended. Hopefully, there are cheaper models.

Not sure who told you about "push poles", but I've never run into
kayaker with a push pole. If you get on rocks, you have a paddle. I
don't even know where you would stow a push ploe. Much better to not
get on the rocks.


YOu have the length of the kayak. A bamboo pole is light, and making an
antenna out of wire won't burden the pole. The real issue, I'd say, is
figuring out something to put on the kayak to hold the pole. For
emergencies, you can probably just have some fishing line tied to the
top of the pole, and hold that as a "guy wire".

If there was some way to hold the oar against the kayak, some clip on
antenna that used the oar as a mast would be better than nothing, and of
course doesn't require an extra pole.

A bit of height probably does make an improvement, after that the "mast"
has to get higher and higher to be useful.

Bamboo poles are not all that light and they get water logged.
Everything on a kayak gets wet.

I was thinking of the bamboo stakes sold for tying plants to. Those are
thin, but so long as the antenna is made of wire, and thus light, would
work fine.

I've used the stakes, because they were handy, to get a TV loop up a bit
higher to scan the channels on the tv set.

But I wasn't thinking of the water, and you're right, they wouldn't hold
up after being kept wet a few times.

How about fibreglass? Those flags seen on bicycles to give some height
for oncoming vehicles, one of those might do. Or I have a vague memory
of seeing such things sold for kayaks, to be seen a bit sooner than when
a bigger boat stumbles on them. If they have them for kayaks, that's a
good route to take, they would come with something to use to mount on
the kayak.

I think the best fiberglass for a marine VHF antenna would be the stuff
you can get when you buy a marine VHF antenna. lol If you are talking
about a simple wire the paddle would be ok. They are typically around 7
foot long. Clip the wire on the end of the paddle and Bob's your uncle.
It's not like you will be transmitting for hours, so you can just hold
the paddle up.

Yesterday I couldn't think of the term for the antenna style they use in
the commercial marine VHF antennas, but I believe it is called
"co-linear" or something like that. It is a bunch of coax sections
connected inner to outer at specific lengths. I have never seen a Ham
recommend using that type. But I guess Hams go more for permanent
installations with ground planes of some type. The co-linear needs no
ground plane I believe.

--

Rick C