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

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

In article , says...

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


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?

AT VHF and above antenna height is more important than power.

I have worked someone in an airplane that was at 30 to 40 thousand feet
thta was using a handy talkey and I was using about 10 watts. He was
almost 200 miles away. The space station has hams on it that are using
about 5 watts and I have heard them many times. Not sure of the
range,but would guess several hundred miles at times.

I know a couple of local guys that used the family radios to talk over
50 miles from one mountain top to another. Not sure of the power but
probably l watt or less.

While going to much higher power, like 500 to 1000 watts will give more
range, just going less than 10 times the power gains very little in
range on vhf and above.

I don't know how to mount an antenna on what he wants to do. There used
to be some coaxial type antennas made that fed from the bottom and did
not require a ground plane.

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 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

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 4/23/2017 2:34 PM, highlandham wrote:

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


Frank - Thanks for the Bluetack reference. It looks quite versatile so I
have ordered it to try.

Cheers,
John N1JLS

On Sun, 23 Apr 2017 20:34:31 +0100, highlandham
wrote:

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).

Nope. You want to tune the antenna for lowest VSWR in the transmit
range (156.0 to 157.5MHz) and take whatever you can get in the 162MHz
receive only region. If you try to tune the antenna for the middle of
the 6 MHz split, you'll end up with lousy VSWR at both extremes where
you want to operate, and good VSWR where you're not operating.

Frank , GM0CSZ / KN6WH in IO87AT
--
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 Sun, 23 Apr 2017 20:34:31 +0100, highlandham
wrote:

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).

Nope. You want to tune the antenna for lowest VSWR in the transmit
range (156.0 to 157.5MHz) and take whatever you can get in the 162MHz
receive only region. If you try to tune the antenna for the middle of
the 6 MHz split, you'll end up with lousy VSWR at both extremes where
you want to operate, and good VSWR where you're not operating.

Frank , GM0CSZ / KN6WH in IO87AT

Thats correct, tune for lowest SWR at the transmit frequency and take
whatever you get at the receive frequency. If you don't , most
transmitters cut the power back, or else you burn up the transmitter.