On Mon, 21 Jan 2008 16:48:25 +0000, larry wrote in
:

John Navas wrote in
:

Marine radars have a limited vertical beam width, and the transponder
should be mounted above or below that vertical pattern. See the
Handbook:

WRONG! Geez, John....

Marine radars have limited HORIZONTAL beamwidth so you can see 3 targets
kinda close together as 3 targets, not 1 blob. They have WIDE VERTICAL
beamwidth so they are pointing at the horizon EVEN WHEN THE BOAT IS HEELED
OVER OR ROLLING!

If they had narrow vertical beamwidth, the only time you'd see the target
is in flat water or at the marina dock!

Read the Handbook. 30° is actually greater than many units.
Garmin GMR 18 HD and GMR 24 HD are 25°. Likewise Furuno and Lowrance,
etc. Check the specs if you still don't believe me.
Many marine radars are gimbal mounted to address the heeling issue.

--
Best regards,
John Navas http:/navasgroup.com

In article ,
larry wrote:

John Navas wrote in
:

Marine radars have a limited vertical beam width, and the transponder
should be mounted above or below that vertical pattern. See the
Handbook:


WRONG! Geez, John....

Marine radars have limited HORIZONTAL beamwidth so you can see 3 targets
kinda close together as 3 targets, not 1 blob. They have WIDE VERTICAL
beamwidth so they are pointing at the horizon EVEN WHEN THE BOAT IS HEELED
OVER OR ROLLING!

If they had narrow vertical beamwidth, the only time you'd see the target
is in flat water or at the marina dock!

"Limited" is such a nondescript word. It really doesn't define what
either of you are trying to say. Marine Radar Antennas, typically have a
25 Degree Vertical Beamwidth, Now to some that may be "Limited", (25°
as opposed to 360°) but when compared to a Marine Radars Horizontal
Beamwidth, (Typically 2° to 6°) it is not "Limited" at all. John's
Point, was that the Radar Transponder MUST be mounted Clearly OUTSIDE
the Vertical Beamwidth of the Onboard Radar, so as to not be triggered
by the operation of the onboard Radar. This is correct.

Bruce in alaska

--
Bruce in alaska
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In article ,
larry wrote:

Bruce in alaska wrote in news:fast-151579.10373820012008
@netnews.worldnet.att.net:

They are mostly used on ships
LARGER than 1200 Tons,

I figured most of these boys and girls were on plastic bubbleboats and
didn't have 8MW air search radars aboard....(c;

Your Squid background is showing Larry, Most Commercial Shipping Vessels
larger than 1200 Gross Tons, will have both XBand and SBand Radar fitted,
and the SBand Radar, these days is used to detect Weather Fronts,
Squalls, Etc. Back in the day, they would be used for Long Distance
Position Fixing, as they had better Range than the fitted XBand Radars.
GPS and Loran have taken over the Position Fixing Job, in modern
Navigating, so SBand, which sees Atmospheric Moisture, much better than
XBand, is used for that. Xband has much better Resolution than SBand,
so it is used, to keep from running into other moving objects, inside
the local path of the vessel. No Ship should be using Radar to keep from
running into non-moving Objects, as GPS, Charts, and the Mark One
Eyeball, should take care of that, and if not then the Master is sorely
lacking in navigation skills.

--
Bruce in alaska
add path after fast to reply

Bruce in alaska wrote in news:fast-EB795C.10155321012008
@netnews.worldnet.att.net:

John's
Point, was that the Radar Transponder MUST be mounted Clearly OUTSIDE
the Vertical Beamwidth of the Onboard Radar, so as to not be triggered
by the operation of the onboard Radar. This is correct

Noone is going to run a radar transponder and radar on the same boat. That
transponder is going to go berserk re-radiating your own radar. There's
all kinds of crazy side lobes on the ****ty PC board antenna on any radome
array. The lobes don't have a lot of power, but sure more than enough
power to set off a transponder, even if you put the damned antenna in the
BILGE!

What a crazy idea....

On Tue, 22 Jan 2008 06:19:37 +0000, larry wrote in
:

Bruce in alaska wrote in news:fast-EB795C.10155321012008
:

John's
Point, was that the Radar Transponder MUST be mounted Clearly OUTSIDE
the Vertical Beamwidth of the Onboard Radar, so as to not be triggered
by the operation of the onboard Radar. This is correct

Noone is going to run a radar transponder and radar on the same boat. That
transponder is going to go berserk re-radiating your own radar. There's
all kinds of crazy side lobes on the ****ty PC board antenna on any radome
array. The lobes don't have a lot of power, but sure more than enough
power to set off a transponder, even if you put the damned antenna in the
BILGE!

What a crazy idea....

Not at all. They serve different purposes, and are complementary.

--
Best regards,
John Navas http:/navasgroup.com

In article ,
larry wrote:
....
Noone is going to run a radar transponder and radar on the same boat.

Is it?

... but sure more than enough
power to set off a transponder, even if you put the damned antenna in the
BILGE!

Of course, but so what. I cannot see anything with my radar up to some
15 metres anyway (assuming 50 ns pulse). The key is if it still responds
to other radars.

What a crazy idea....

Why? The radar expands what I see, and the transponder expands, what
others with a radar see.

I have seen how unreliable echos from glass fibre reinforced polyester
boats are (and how unreliable echos at least smaller passive radar
reflectors of the 90° aluminum sheets type give on quiet waters).

Small wonder aircraft all have a transponder.

Marc

--
remove bye and from mercial to get valid e-mail
http://www.heusser.com

Marc Heusser d wrote in
:

I have seen how unreliable echos from glass fibre reinforced polyester
boats are (and how unreliable echos at least smaller passive radar
reflectors of the 90ø aluminum sheets type give on quiet waters).



If you're going to buy anything to make you a big target on the SHIPS and
large yachts....buy an AIS TRANSPONDER, which makes you as big as an
aircraft carrier.

All ship over 300 gross tons now have full AIS aboard, as do the big
yachts, to make them look big.

Every boat that leaves the harbor should be AIS equipped, now.

Of course, every harbor should have:
http://www.aisliverpool.org.uk/
too. It'll come, eventually.

larry wrote in news:Xns9A2D69494A46Bnoonehomecom@
208.49.80.253:

All ship over 300 gross tons now have full AIS aboard, as do the big
yachts, to make them look big.


Name: Grand Esmeralda
MMSI: 636012671 [LR]
IMO: 8920062
Callsign: A8GX9
Speed/Dir: 14.2 kts / 278° W
Status: Underway
Dest: Mobile,Alabama
ETA: Feb06 06:00
Type: Cargo (70)
Size: 225m x 32m x 7.3m
Received: 15:17:50 22 Jan 08 GMT

Just snapped his picture on the webpage. Long trip to Mobile from
Liverpool. He just left.

Not only would the mate driving that tanker know you were there....He'd
know a lot about you, too, and his computer would make sure he didn't
collide with you unless you did something really stupid.

We could even call him with his callsign...

larry wrote:
Marc Heusser d wrote in
:

I have seen how unreliable echos from glass fibre reinforced polyester
boats are (and how unreliable echos at least smaller passive radar
reflectors of the 90ø aluminum sheets type give on quiet waters).



If you're going to buy anything to make you a big target on the SHIPS and
large yachts....buy an AIS TRANSPONDER, which makes you as big as an
aircraft carrier.

All ship over 300 gross tons now have full AIS aboard, as do the big
yachts, to make them look big.


I'm still waiting to upgrade my AIS receiver for a
transponder. At least I can see and identify a threat and
call by name on VHF.

From 'The Pilot' the magazine of the United Kingdom
Maritime Pilots' Association, quoting a working harbour pilot:
"With respect to the type of equipment installed, the
overwhelming majority of vessels are fitted with the minimum
required to comply with carriage regulations! These are
small alpha numeric displays which at the absolute basic
level have to display at least three targets. I have seen
such minimal three line units on ships and for all practical
purposes they are totally useless. Other systems cram a list
of many targets into the small display (typically 9cm x
12cm) which renders them illegible and again these are
totally useless.
It is of extreme importance to the Class B user to be
aware that there is no statutory requirement for SOLAS
vessels to be able to display AIS targets on a screen merely
a requirement to provide a simple alphanumeric Minimum
Keyboard and Display (MKD). To meet the minimum requirements
this display need show no more than three ships at any one
time detailing bearing, range and name of ship. Therefore
Class B users must understand that their vessel may not be
appearing as a 'bright beacon' on the displays of the
majority of SOLAS vessels. Although IMO requires all new
radars fitted after 1 July 2008 to have good AIS display
capabilities, existing radars will not have to be upgraded
and so it will be many years before AIS data can be
effectively used for navigation on many SOLAS vessels."

On Tue, 22 Jan 2008 15:10:52 +0000, larry wrote in
:

Marc Heusser d wrote in
:

I have seen how unreliable echos from glass fibre reinforced polyester
boats are (and how unreliable echos at least smaller passive radar
reflectors of the 90ø aluminum sheets type give on quiet waters).

If you're going to buy anything to make you a big target on the SHIPS and
large yachts....buy an AIS TRANSPONDER, which makes you as big as an
aircraft carrier.

All ship over 300 gross tons now have full AIS aboard, as do the big
yachts, to make them look big.

True of commercial ships, but *not* of many pleasure craft.

Every boat that leaves the harbor should be AIS equipped, now.

"Let them eat cake?" And small comfort when one of them collides with
you. Until the world comes around to your PoV, a radar transponder is a
highly recommended safety device whether you have radar or not. I would
still use one even with AIS -- you can never have enough backup --
depending on a single device is just plain foolish.

--
Best regards,
John Navas http:/navasgroup.com