In article , rickman wrote:

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.

"Colinear" or "collinear", depending on whom you read. They're
basically a vertically-stacked array of individual radiating sections.

http://www.rason.org/Projects/collant/collant.htm

There are quite a few commercial ham antennas which use this approach
(the "Stationmaster" probably being the best known). They're fairly
popular for use on the 70 cm ham band, and some repeaters and base
stations use them on 2 meters.

This design is generally used when you want a substantial amount of
directional gain, and are willing to pay the price (length) for it.

I don't think this design would be a great choice for a kayak antenna,
because the individual coax sections in the "stack" are a
half-wavelength long (at the coax's velocity factor) and there are
usually quarter-wave sections at the top and bottom. The shortest
2-meter collinear (one half-wave section and two quarter-wave) would
be 2 meters in length - over six feet - and a marine VHF antenna
wouldn't be much shorter.

With a collinear of the type shown in the above link, you'd need to
mast-mount it up some distance - the bottom quarter-wave tube is
RF-hot, and if its bottom end is near water (or anything grounded) it
would tend to de-tune the antenna.

As others have noted, the OP really doesn't need a high-gain antenna.

On 4/25/2017 3:19 PM, Dave Platt wrote:
In article , rickman wrote:

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.

"Colinear" or "collinear", depending on whom you read. They're
basically a vertically-stacked array of individual radiating sections.

http://www.rason.org/Projects/collant/collant.htm

There are quite a few commercial ham antennas which use this approach
(the "Stationmaster" probably being the best known). They're fairly
popular for use on the 70 cm ham band, and some repeaters and base
stations use them on 2 meters.

This design is generally used when you want a substantial amount of
directional gain, and are willing to pay the price (length) for it.

I don't think this design would be a great choice for a kayak antenna,
because the individual coax sections in the "stack" are a
half-wavelength long (at the coax's velocity factor) and there are
usually quarter-wave sections at the top and bottom. The shortest
2-meter collinear (one half-wave section and two quarter-wave) would
be 2 meters in length - over six feet - and a marine VHF antenna
wouldn't be much shorter.

With a collinear of the type shown in the above link, you'd need to
mast-mount it up some distance - the bottom quarter-wave tube is
RF-hot, and if its bottom end is near water (or anything grounded) it
would tend to de-tune the antenna.

As others have noted, the OP really doesn't need a high-gain antenna.

I think the real problem is this antenna for 2 meter operation is 20
feet long! For marine VHF it can't be used on shore, so hanging it from
a tree would not work. When you say using a single half wave section
wouldn't be much different from a marine VHF antenna, what type of
antenna would a marine VHF antenna be? I thought they used a colinear
design.

--

Rick C

rickman wrote:
I don't think this design would be a great choice for a kayak antenna,
because the individual coax sections in the "stack" are a
half-wavelength long (at the coax's velocity factor) and there are
usually quarter-wave sections at the top and bottom. The shortest
2-meter collinear (one half-wave section and two quarter-wave) would
be 2 meters in length - over six feet - and a marine VHF antenna
wouldn't be much shorter.

With a collinear of the type shown in the above link, you'd need to
mast-mount it up some distance - the bottom quarter-wave tube is
RF-hot, and if its bottom end is near water (or anything grounded) it
would tend to de-tune the antenna.

As others have noted, the OP really doesn't need a high-gain antenna.

I think the real problem is this antenna for 2 meter operation is 20
feet long! For marine VHF it can't be used on shore, so hanging it from
a tree would not work. When you say using a single half wave section
wouldn't be much different from a marine VHF antenna, what type of
antenna would a marine VHF antenna be? I thought they used a colinear
design.

I wonder, why is the "2 meter band" not called the "6 1/2 feet band"
in the USA? This alternating between meters and feet is getting a
bit funny.

On 4/25/2017 4:24 PM, Rob wrote:
rickman wrote:
I don't think this design would be a great choice for a kayak antenna,
because the individual coax sections in the "stack" are a
half-wavelength long (at the coax's velocity factor) and there are
usually quarter-wave sections at the top and bottom. The shortest
2-meter collinear (one half-wave section and two quarter-wave) would
be 2 meters in length - over six feet - and a marine VHF antenna
wouldn't be much shorter.

With a collinear of the type shown in the above link, you'd need to
mast-mount it up some distance - the bottom quarter-wave tube is
RF-hot, and if its bottom end is near water (or anything grounded) it
would tend to de-tune the antenna.

As others have noted, the OP really doesn't need a high-gain antenna.

I think the real problem is this antenna for 2 meter operation is 20
feet long! For marine VHF it can't be used on shore, so hanging it from
a tree would not work. When you say using a single half wave section
wouldn't be much different from a marine VHF antenna, what type of
antenna would a marine VHF antenna be? I thought they used a colinear
design.

I wonder, why is the "2 meter band" not called the "6 1/2 feet band"
in the USA? This alternating between meters and feet is getting a
bit funny.

Why is the 70 cm band not the 700 mm band or the 0.07 meter band? Not
sure what issue you have with feet other than it not being familiar
perhaps. As much as I use metric, feet and inches are still ingrained
in my soul. When I look at a flag pole I don't think, geeze, that's 10
meters high! I think 30 feet. It's that simple.

--

Rick C

rickman wrote:
On 4/25/2017 4:24 PM, Rob wrote:
rickman wrote:
I don't think this design would be a great choice for a kayak antenna,
because the individual coax sections in the "stack" are a
half-wavelength long (at the coax's velocity factor) and there are
usually quarter-wave sections at the top and bottom. The shortest
2-meter collinear (one half-wave section and two quarter-wave) would
be 2 meters in length - over six feet - and a marine VHF antenna
wouldn't be much shorter.

With a collinear of the type shown in the above link, you'd need to
mast-mount it up some distance - the bottom quarter-wave tube is
RF-hot, and if its bottom end is near water (or anything grounded) it
would tend to de-tune the antenna.

As others have noted, the OP really doesn't need a high-gain antenna.

I think the real problem is this antenna for 2 meter operation is 20
feet long! For marine VHF it can't be used on shore, so hanging it from
a tree would not work. When you say using a single half wave section
wouldn't be much different from a marine VHF antenna, what type of
antenna would a marine VHF antenna be? I thought they used a colinear
design.

I wonder, why is the "2 meter band" not called the "6 1/2 feet band"
in the USA? This alternating between meters and feet is getting a
bit funny.

Why is the 70 cm band not the 700 mm band or the 0.07 meter band? Not
sure what issue you have with feet other than it not being familiar
perhaps. As much as I use metric, feet and inches are still ingrained
in my soul. When I look at a flag pole I don't think, geeze, that's 10
meters high! I think 30 feet. It's that simple.

Maybe yes, but it should be obvious that when you are discussing
antennas for the "2 meter band" their dimensions will be nice multiples
of those same 2 meters.

When I think about a "halfwave dipole for 2 meters" I think "1 meter",
not "3 1/4 feet" or "39 inches". So when you want to discuss antenna
sizes I think it would be more convenient to use the same units all
around.

For me, that of course is meters. Scaling like "milli" or "centi"
is natural in the metric system, I don't have to think about that.
(contrary to converting feet to inches or meters to feet)

On 4/26/2017 3:55 AM, Rob wrote:
rickman wrote:
On 4/25/2017 4:24 PM, Rob wrote:
rickman wrote:
I don't think this design would be a great choice for a kayak antenna,
because the individual coax sections in the "stack" are a
half-wavelength long (at the coax's velocity factor) and there are
usually quarter-wave sections at the top and bottom. The shortest
2-meter collinear (one half-wave section and two quarter-wave) would
be 2 meters in length - over six feet - and a marine VHF antenna
wouldn't be much shorter.

With a collinear of the type shown in the above link, you'd need to
mast-mount it up some distance - the bottom quarter-wave tube is
RF-hot, and if its bottom end is near water (or anything grounded) it
would tend to de-tune the antenna.

As others have noted, the OP really doesn't need a high-gain antenna.

I think the real problem is this antenna for 2 meter operation is 20
feet long! For marine VHF it can't be used on shore, so hanging it from
a tree would not work. When you say using a single half wave section
wouldn't be much different from a marine VHF antenna, what type of
antenna would a marine VHF antenna be? I thought they used a colinear
design.

I wonder, why is the "2 meter band" not called the "6 1/2 feet band"
in the USA? This alternating between meters and feet is getting a
bit funny.

Why is the 70 cm band not the 700 mm band or the 0.07 meter band? Not
sure what issue you have with feet other than it not being familiar
perhaps. As much as I use metric, feet and inches are still ingrained
in my soul. When I look at a flag pole I don't think, geeze, that's 10
meters high! I think 30 feet. It's that simple.

Maybe yes, but it should be obvious that when you are discussing
antennas for the "2 meter band" their dimensions will be nice multiples
of those same 2 meters.

When I think about a "halfwave dipole for 2 meters" I think "1 meter",
not "3 1/4 feet" or "39 inches". So when you want to discuss antenna
sizes I think it would be more convenient to use the same units all
around.

For me, that of course is meters. Scaling like "milli" or "centi"
is natural in the metric system, I don't have to think about that.
(contrary to converting feet to inches or meters to feet)

So what should I have said rather than 20 feet?

--

Rick C

In article ,
Rob wrote:

I wonder, why is the "2 meter band" not called the "6 1/2 feet band"
in the USA? This alternating between meters and feet is getting a
bit funny.

Fewer syllables? :-)

The ham bands have always been described in terms of meters, I
believe. Since amateur radio use is defined to a significant extent
by international treaty, and since the U.S. is very definitely in the
minority in terms of measurement units, it's just easier for all of
the hams to use the same (metric) terminology.

Also, wavelength and frequency convert back and forth a bit more
conveniently in metric, at least in terms of rough numbers (divide 300
by one, to get the other). Hence, "2-meter" is around 150 MHz.

On 25 Apr 2017 20:24:44 GMT, Rob wrote:

I wonder, why is the "2 meter band" not called the "6 1/2 feet band"
in the USA? This alternating between meters and feet is getting a
bit funny.

Chuckle. Yeah, that's a problem. I sometimes irritate the local hams
by referring to various HF bands by the equivalent feet, yards, or
cubits. When asked which is the right way, my usual answer is when
test equipment manufacturers start labeling their equipment in units
of feet or meters, I might consider using those designations. Until
then, since most test equipment is labeled by the frequency, I'll use
Hz, KHz, MHz, GHz, etc.

Incidentally, if you need more confusion, there are the various
microwave frequency bands designed by letters, such as DBS
broadcasting is on K and Ku bands in the US. Then, there are bands
that are designated by their service type or spectrum auction block
numbers:
http://wireless.fcc.gov/auctions/default.htm?job=bandplans


--
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 , rickman wrote:

I think the real problem is this antenna for 2 meter operation is 20
feet long!

Yup. Great for side-mounting on a tower, so-so for top-mounting on a
tower or mast (it'll sway in the breeze and this can wear out the
solder junctions), not so great for vehicle mounting, and downright
impractical for a hand-held :-)

For marine VHF it can't be used on shore, so hanging it from
a tree would not work. When you say using a single half wave section
wouldn't be much different from a marine VHF antenna, what type of
antenna would a marine VHF antenna be? I thought they used a colinear
design.

For "shortened" antennas, what you'll often find is that they're
"loaded" antennas. You can significantly shorten a radiating element,
and still have resonance, by adding an inductor of some sort - the
shortened element has capacitive reactance, and the inductor's
reactance (equal magnitude, opposite sign) cancels it out.

One way to do this is to wind the element itself into a spiral... this
adds inductance and lets you use a longer piece of wire
(i.e. something close to a quarter-wave).

Most "rubber duck" antennas are of this sort - they often have an
inductor in the base (right by the radio), and the whip consists of a
wire wound spiral-fashion around some sort of insulating core. If you
buy a hand-held marine-VHF radio, that's very likely what you'll get.

An example:

http://www.gandermountain.com/modper...ntenna&i=91538

Note they call it "Heliflex" - probably shorthand for "helically wound
flexible". It's only 1' long.

http://www.gandermountain.com/modper...ntenna&i=91513

This one is 6', or almost 2 meters. It might contain some sort of
center-fed dipole (fed up through the center of the lower element), or
it might be sort of the equivalent of a J-pole (half-wave or 5/8-wave
radiator with a matching stub or coil at the bottom).

On 4/25/2017 5:43 PM, Dave Platt wrote:
In article , rickman wrote:

I think the real problem is this antenna for 2 meter operation is 20
feet long!

Yup. Great for side-mounting on a tower, so-so for top-mounting on a
tower or mast (it'll sway in the breeze and this can wear out the
solder junctions), not so great for vehicle mounting, and downright
impractical for a hand-held :-)

For marine VHF it can't be used on shore, so hanging it from
a tree would not work. When you say using a single half wave section
wouldn't be much different from a marine VHF antenna, what type of
antenna would a marine VHF antenna be? I thought they used a colinear
design.

For "shortened" antennas, what you'll often find is that they're
"loaded" antennas. You can significantly shorten a radiating element,
and still have resonance, by adding an inductor of some sort - the
shortened element has capacitive reactance, and the inductor's
reactance (equal magnitude, opposite sign) cancels it out.

One way to do this is to wind the element itself into a spiral... this
adds inductance and lets you use a longer piece of wire
(i.e. something close to a quarter-wave).

Most "rubber duck" antennas are of this sort - they often have an
inductor in the base (right by the radio), and the whip consists of a
wire wound spiral-fashion around some sort of insulating core. If you
buy a hand-held marine-VHF radio, that's very likely what you'll get.

An example:

http://www.gandermountain.com/modper...ntenna&i=91538

Note they call it "Heliflex" - probably shorthand for "helically wound
flexible". It's only 1' long.

http://www.gandermountain.com/modper...ntenna&i=91513

This one is 6', or almost 2 meters. It might contain some sort of
center-fed dipole (fed up through the center of the lower element), or
it might be sort of the equivalent of a J-pole (half-wave or 5/8-wave
radiator with a matching stub or coil at the bottom).

Interesting. Any idea what the specs mean?

Gain 3dBi
"Marine Gain" 6dB

I know what dBi is, but what is Marine Gain? Is there some reference
antenna they use such as the rubber ducky?

--

Rick C