NOYB wrote:
"Wayne.B" wrote in message
...
On 13 Jan 2006 09:56:30 -0800, "
wrote:

According to post in this newsgroup, we need a metal plate for
grounding if we use a 3dB antenna, and a fiberglass boat doesn't have
it. My boat is a fiberglass boat. What's the alternative? Does this
mean that I cannot use 3dB antenna?

There is no need for a ground with a VHF antenna.

Either the 3 db or 6 db antenna will be adequate for near shore
coastal operation.


I'm with Wayne on this one.

The dB rating plays a relatively minor role in the distance the signal
travels. The height of the transmitting antenna plays a larger role. But
the height of the receiving antenna is the most important element.

Example:
A 3' antenna mounted on the top of the gunwale of a small boat might be 5'
above the water line. It can travel only 5 miles to another antenna that
is only 5' off the water...but can travel 15 miles to an antenna that is
100' high (like at a Coast Guard station).

An 8' antenna mounted on the same gunnel can travel 9 miles to another
antenna that is only 5' off the water (big difference!), but only travels 18
miles to that 100' antenna (a not so big difference from the 3' antenna).

If the CG antenna is 250' above sea level (mounted on a tower on a mountain
for example), the 3' antenna can travel 23 miles...and the 8' travels 25
miles.

So the question is...
Who do you want to call with that radio?

Another boat within 5 miles? Then either antenna is fine.

The Coast Guard when you're 10-15 miles from shore? Then either antenna is
fine once again.

Here's a good link to explain this further:
http://www.yachtworks.net/Store/antennas.htm

Thanks for the explanation of the reason why a 3-ft 3dB antenna may be
all I need.

I go home and check the possible location for a 8-ft antenna in my
18-ft boat. I have a feeling that a 8-ft antenna is just too long. If
I mount it in the front rail of the T-top and set the antenna at a
45-degree angle toward the stern, the 8-ft antenna will still stick out
covering the entire deck in the stern of my boat. This is going to be
a problem if I want to cast from the deck in the stern of my boat
because my fishing rod "may" hit the antenna. A 3-ft antenna that is
pointing straight up will not have this problem.

A 3-ft antenna mounted on the T-top will be as much as 9-ft above the
water level. According to this formula:
range-in-miles = square-root-of-height-above-water-in-feet x 1.42
I should expect to get the range of up to 4.26 miles. This seems to be
more than enough because I will be boating and fishing near the shore
(not more than a couple miles from the shore), and the coast guard with
their very tall antenna should be able to reach me.

OK, seem like I should get a 3-ft 3dB antenna.

Jay Chan

"NOYB" wrote in message
ink.net...

" JimH" jimh_osudad@yahooDOT comREMOVETHIS wrote in message
...

"NOYB" wrote in message
ink.net...

" JimH" jimh_osudad@yahooDOT comREMOVETHIS wrote in message
...

"NOYB" wrote in message
ink.net...

"Shortwave Sportfishing" wrote in message
...
On Fri, 13 Jan 2006 23:35:25 GMT, "NOYB" wrote:


"Wayne.B" wrote in message
news:184gs1psncof0p2otitab109lbsdrmpimi@4ax .com...
On 13 Jan 2006 09:56:30 -0800, "
wrote:

According to post in this newsgroup, we need a metal plate for
grounding if we use a 3dB antenna, and a fiberglass boat doesn't
have
it. My boat is a fiberglass boat. What's the alternative? Does
this
mean that I cannot use 3dB antenna?

There is no need for a ground with a VHF antenna.

Either the 3 db or 6 db antenna will be adequate for near shore
coastal operation.


I'm with Wayne on this one.

The dB rating plays a relatively minor role in the distance the
signal
travels. The height of the transmitting antenna plays a larger role.
But
the height of the receiving antenna is the most important element.

Example:
A 3' antenna mounted on the top of the gunwale of a small boat might
be 5'
above the water line. It can travel only 5 miles to another antenna
that
is only 5' off the water...but can travel 15 miles to an antenna that
is
100' high (like at a Coast Guard station).

An 8' antenna mounted on the same gunnel can travel 9 miles to
another
antenna that is only 5' off the water (big difference!), but only
travels 18
miles to that 100' antenna (a not so big difference from the 3'
antenna).

If the CG antenna is 250' above sea level (mounted on a tower on a
mountain
for example), the 3' antenna can travel 23 miles...and the 8' travels
25
miles.

So the question is...
Who do you want to call with that radio?

Another boat within 5 miles? Then either antenna is fine.

The Coast Guard when you're 10-15 miles from shore? Then either
antenna is
fine once again.

Here's a good link to explain this further:
http://www.yachtworks.net/Store/antennas.htm

finally - a civilian who gets it.

That's the engineer in me. I like to read how things work before
making my purchases.




Looking at specs is fine. But what happens when the boat, intended for
only near shore use, loses power when at the fringe range of the 3 foot
antenna and there are no boaters anywhere close?

The point I was making is that the 3' antenna will reach a CG tower more
than 15 miles away...and the 8' antenna will reach only about 3 miles
further. That's not really an appreciable difference unless his fishing
grounds are consistently in the 16-18 mile range.

Besides, if he's out in an 18' boat more than 15 miles from shore, he
better be carrying an EPIRB...and filing a float plan. Should he fail
to return as planned, a CG aircraft will pick his radio up from nearly
30 miles or more...no matter how big his antenna is.

Keep in mind that the antenna on passing ships/shrimp boats/etc. are at
least 30-50' above the water...meaning that his 3' antenna will reach
them almost as well as the 8' antenna.

As I said before, the height of the receiving antenna on most vessels
that are going to render assistance has a greater influence on your
radio's effective range than the height of your own antenna.

I regularly hear CG broadcasts coming out of St. Pete...and I'm 160
miles from them. Granted, they're using higher power equipment and very
tall broadcast towers (perhaps broadcasting from aircraft), but I hear
them on my boat with the 3' antenna just as well as the Grady with an 8'
antenna on top of the hardtop.


NOYB, I hear what you are saying, but..........being able to broadcast an
additional 3 miles while drifting further out to sea with a dead engine
in the ocean can be a life saver.

I often do a simple cost/benefit analysis when trying to make a decision
like this, and in Jay's case it is a no brainer.

When I bought my 17' Whaler, it had an 8' antenna mounted on top the
gunwale. My brother has a 3' on the railing of the center console of his
18' Whaler.

It's not about the cost. I'd go with the 3' on top of the railing of the
center console, because it's out of the way when fighting a fish...and the
height above the water line is only a couple of feet less than my 8'.




Fair enough. I cannot dispute your real life salt water experience.

wrote:
JimH wrote:
wrote in message
ups.com...
I am going to add a fix-mounted VHF radio in my boat. I would like to
know whether I should get a 3dB 3-ft antenna or a 6dB 8-ft antenna to
mount on the T-top. My questions a

- Books and people in this newsgroup recommend 6dB 8-ft antenna for a
small powered boat. This sounds good. But I am wondering whether a
8-ft antenna is too large for my 18-ft boat.


Nope.


Will this make the boat
"look" very top-heavy?


Nope.


Do people really use a 8-ft antenna in a small
boat like mine?

Yep.



- The other alternative is a 3dB 3-ft antenna and accepting the
reduced range. Does a 3dB antenna provide a good enough range given
the fact that I won't go too far away from the shore (because the boat
is considered as a "bay boat")?


Purchase the 8 footer to get the greatest range.


- According to post in this newsgroup, we need a metal plate for
grounding if we use a 3dB antenna, and a fiberglass boat doesn't have
it. My boat is a fiberglass boat. What's the alternative? Does this
mean that I cannot use 3dB antenna?

Thanks for any info in advance.

Jay Chan

Thanks for the useful info. I will go ahead to order a 6dB 8-ft
antenna and a fix-mounted VHF radio.

Jay Chan

Well, I change my mind, and I will get a 3-ft antenna instead. I
didn't take into the account that the 8-ft antenna can become a problem
when I cast with my fishing rod.

I have a feeling that if mine is a 21-ft boat with a taller T-top (like
the Mako center console that I see in ad), I would have chosen a 8-ft
antenna. But mine is a small 18-ft boat, and I have a feeling that it
just doesn't make the cut for a 8-ft antenna.

Jay Chan

wrote in message
oups.com...
NOYB wrote:
"Wayne.B" wrote in message
...
On 13 Jan 2006 09:56:30 -0800, "
wrote:

According to post in this newsgroup, we need a metal plate for
grounding if we use a 3dB antenna, and a fiberglass boat doesn't have
it. My boat is a fiberglass boat. What's the alternative? Does this
mean that I cannot use 3dB antenna?

There is no need for a ground with a VHF antenna.

Either the 3 db or 6 db antenna will be adequate for near shore
coastal operation.


I'm with Wayne on this one.

The dB rating plays a relatively minor role in the distance the signal
travels. The height of the transmitting antenna plays a larger role. But
the height of the receiving antenna is the most important element.

Example:
A 3' antenna mounted on the top of the gunwale of a small boat might be
5'
above the water line. It can travel only 5 miles to another antenna
that
is only 5' off the water...but can travel 15 miles to an antenna that is
100' high (like at a Coast Guard station).

An 8' antenna mounted on the same gunnel can travel 9 miles to another
antenna that is only 5' off the water (big difference!), but only travels
18
miles to that 100' antenna (a not so big difference from the 3' antenna).

If the CG antenna is 250' above sea level (mounted on a tower on a
mountain
for example), the 3' antenna can travel 23 miles...and the 8' travels 25
miles.

So the question is...
Who do you want to call with that radio?

Another boat within 5 miles? Then either antenna is fine.

The Coast Guard when you're 10-15 miles from shore? Then either antenna
is
fine once again.

Here's a good link to explain this further:
http://www.yachtworks.net/Store/antennas.htm

Thanks for the explanation of the reason why a 3-ft 3dB antenna may be
all I need.

I go home and check the possible location for a 8-ft antenna in my
18-ft boat. I have a feeling that a 8-ft antenna is just too long. If
I mount it in the front rail of the T-top and set the antenna at a
45-degree angle toward the stern, the 8-ft antenna will still stick out
covering the entire deck in the stern of my boat. This is going to be
a problem if I want to cast from the deck in the stern of my boat
because my fishing rod "may" hit the antenna. A 3-ft antenna that is
pointing straight up will not have this problem.

A 3-ft antenna mounted on the T-top will be as much as 9-ft above the
water level. According to this formula:
range-in-miles = square-root-of-height-above-water-in-feet x 1.42
I should expect to get the range of up to 4.26 miles.

But that's only to reach another antenna that is right at the level of the
water. If there were another boat with an antenna 9' above the water, you'd
carry at least twice that distance.

Around 1/13/2006 8:33 PM, wrote:

I have a feeling that if mine is a 21-ft boat with a taller T-top (like
the Mako center console that I see in ad), I would have chosen a 8-ft
antenna. But mine is a small 18-ft boat, and I have a feeling that it
just doesn't make the cut for a 8-ft antenna.

shrugs

I've got an 8' antenna and a 14' boat. I figure that I need every inch
of range I can get...

http://home.comcast.net/~galmgren/gl...t_7-04_004.jpg

--
~/Garth
(.Sig broken)

"Harry Krause" wrote in message
...
Garth Almgren wrote:
Around 1/13/2006 8:33 PM, wrote:

I have a feeling that if mine is a 21-ft boat with a taller T-top (like
the Mako center console that I see in ad), I would have chosen a 8-ft
antenna. But mine is a small 18-ft boat, and I have a feeling that it
just doesn't make the cut for a 8-ft antenna.

shrugs

I've got an 8' antenna and a 14' boat. I figure that I need every inch
of range I can get...

http://home.comcast.net/~galmgren/gl...t_7-04_004.jpg



Perhaps it is time to introduce Harry's Helium VHF Antenna kit...a
tethered balloon cum antenna for emergency use you release when you
absolutely have to reach someone on your VHF. Comes with 1000' feet of
string.

$999.99, plus shipping and handling.

Could include the pickup harness we had when I was in the air force.
Balloon and a harness, and the pickup plane plucked you from the ground or
water at high speed.

"Garth Almgren" wrote in message
...
Around 1/13/2006 8:33 PM, wrote:

I have a feeling that if mine is a 21-ft boat with a taller T-top (like
the Mako center console that I see in ad), I would have chosen a 8-ft
antenna. But mine is a small 18-ft boat, and I have a feeling that it
just doesn't make the cut for a 8-ft antenna.

shrugs

I've got an 8' antenna and a 14' boat. I figure that I need every inch
of range I can get...

http://home.comcast.net/~galmgren/gl...t_7-04_004.jpg

--
~/Garth
(.Sig broken)

That is what I have been saying all along. I see no reason not to go with
the antenna that will increase your transmission range.

NOYB wrote:
wrote in message
oups.com...
NOYB wrote:
"Wayne.B" wrote in message
...
On 13 Jan 2006 09:56:30 -0800, "
wrote:

According to post in this newsgroup, we need a metal plate for
grounding if we use a 3dB antenna, and a fiberglass boat doesn't have
it. My boat is a fiberglass boat. What's the alternative? Does this
mean that I cannot use 3dB antenna?

There is no need for a ground with a VHF antenna.

Either the 3 db or 6 db antenna will be adequate for near shore
coastal operation.


I'm with Wayne on this one.

The dB rating plays a relatively minor role in the distance the signal
travels. The height of the transmitting antenna plays a larger role. But
the height of the receiving antenna is the most important element.

Example:
A 3' antenna mounted on the top of the gunwale of a small boat might be
5'
above the water line. It can travel only 5 miles to another antenna
that
is only 5' off the water...but can travel 15 miles to an antenna that is
100' high (like at a Coast Guard station).

An 8' antenna mounted on the same gunnel can travel 9 miles to another
antenna that is only 5' off the water (big difference!), but only travels
18
miles to that 100' antenna (a not so big difference from the 3' antenna).

If the CG antenna is 250' above sea level (mounted on a tower on a
mountain
for example), the 3' antenna can travel 23 miles...and the 8' travels 25
miles.

So the question is...
Who do you want to call with that radio?

Another boat within 5 miles? Then either antenna is fine.

The Coast Guard when you're 10-15 miles from shore? Then either antenna
is
fine once again.

Here's a good link to explain this further:
http://www.yachtworks.net/Store/antennas.htm

Thanks for the explanation of the reason why a 3-ft 3dB antenna may be
all I need.

I go home and check the possible location for a 8-ft antenna in my
18-ft boat. I have a feeling that a 8-ft antenna is just too long. If
I mount it in the front rail of the T-top and set the antenna at a
45-degree angle toward the stern, the 8-ft antenna will still stick out
covering the entire deck in the stern of my boat. This is going to be
a problem if I want to cast from the deck in the stern of my boat
because my fishing rod "may" hit the antenna. A 3-ft antenna that is
pointing straight up will not have this problem.

A 3-ft antenna mounted on the T-top will be as much as 9-ft above the
water level. According to this formula:
range-in-miles = square-root-of-height-above-water-in-feet x 1.42
I should expect to get the range of up to 4.26 miles.

But that's only to reach another antenna that is right at the level of the
water. If there were another boat with an antenna 9' above the water, you'd
carry at least twice that distance.

I didn't know this (I must have skimmed through the forumla too
quickly). I assumed that the number from the calculation was for
communicating with another antenna that had the same height as the
transmitting antenna. Thanks for correcting this wrong assumption.

I am very glad that you have given me the correct definition of the
formula (to calculate the effective range). Now I know the reason why
the calculated effective range doesn't match the number shown on the
book (because the number shown on the book takes into account of the
antenna height of the receiving party).

Jay Chan

" JimH" jimh_osudad@yahooDOT comREMOVETHIS wrote in message
...

"NOYB" wrote in message
ink.net...

"Shortwave Sportfishing" wrote in message
...
On Fri, 13 Jan 2006 23:35:25 GMT, "NOYB" wrote:


"Wayne.B" wrote in message
...
On 13 Jan 2006 09:56:30 -0800, "
wrote:

According to post in this newsgroup, we need a metal plate for
grounding if we use a 3dB antenna, and a fiberglass boat doesn't have
it. My boat is a fiberglass boat. What's the alternative? Does
this
mean that I cannot use 3dB antenna?

There is no need for a ground with a VHF antenna.

Either the 3 db or 6 db antenna will be adequate for near shore
coastal operation.


I'm with Wayne on this one.

The dB rating plays a relatively minor role in the distance the signal
travels. The height of the transmitting antenna plays a larger role.
But
the height of the receiving antenna is the most important element.

Example:
A 3' antenna mounted on the top of the gunwale of a small boat might be
5'
above the water line. It can travel only 5 miles to another antenna
that
is only 5' off the water...but can travel 15 miles to an antenna that
is
100' high (like at a Coast Guard station).

An 8' antenna mounted on the same gunnel can travel 9 miles to another
antenna that is only 5' off the water (big difference!), but only
travels
18
miles to that 100' antenna (a not so big difference from the 3'
antenna).

If the CG antenna is 250' above sea level (mounted on a tower on a
mountain
for example), the 3' antenna can travel 23 miles...and the 8' travels
25
miles.

So the question is...
Who do you want to call with that radio?

Another boat within 5 miles? Then either antenna is fine.

The Coast Guard when you're 10-15 miles from shore? Then either
antenna
is
fine once again.

Here's a good link to explain this further:
http://www.yachtworks.net/Store/antennas.htm

finally - a civilian who gets it.

That's the engineer in me. I like to read how things work before making
my purchases.




Looking at specs is fine. But what happens when the boat, intended for
only
near shore use, loses power when at the fringe range of the 3 foot antenna
and there are no boaters anywhere close?

I see no downside with going with the 8 foot antenna.



The downside of the higher gain antenna, is that when the the seas are
rolling the energy radiated from the antenna on a small boat will be
directed toward the water or toward the sky. Why not mount the 3 dB antenna
high, or use an extension?