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