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-   -   Opinions on Radars (https://www.boatbanter.com/cruising/28111-opinions-radars.html)

Dan Best February 15th 05 08:35 PM

I have two singout arms in my hatchway. The raday display is on one and
a gps/fish finder is on the other. Unfortunately, there just wasn't
quite enough room to attach both devices to just one arm, my hatch just
isn't tall enough to have them one above the other. When both are
deployed so the helmsman can see them, it's a little inconvienient since
to in or out of the hatch, you have to either carefully step over them
or swing one of them out of the way. In reality, this is not a big deal
since the radar is only rarely used (but when we do use it, we are
REALLY glad we have it).

Fair winds - Dan Best

rhys wrote:
It would tend to "compound errors", certainly. I've installed
something on my current boat, however, that I haven't seen before. I
got a gooseneck armature from an old draftsman's flourescent light and
clamped it so that it swings into the companionway. It can be lashed
in position with shock cord, if needed, but usually the friction knobs
do the trick.

On the armature I've secured a handheld GPS on "ship's power" (a 12 V
cigarette lighter style adapter). This means I can reference the GPS
quickly without using my hands, and without it being loose in the
cockpit, without eating batteries (they go through AAs in 2-3 hours of
continuous use), without losing "satellite lock" (because they are on
all the time and in the companionway can "see" enough sky).

Other advantages are (mostly) out of the weather (a ziplock bag will
do the trick here as well).

Of course, I have a tiller, which means I am standing most of the time
by the companionway near the winches and aft of the traveller on the
cabin-top.

I wonder, however, if my "armature idea" would be useful for any
similar devices, as opposed to a "hard-mount" at the wheel? If, for
instance, you had a 15" LCD panel and a wireless mouse, the panel
could be some distance away and still be readable.

R.


Bruce in Alaska February 15th 05 08:46 PM

In article ,
renewontime dot com wrote:

The metal mast and rigging may not obscure your radar display
(an empty "shadow area"), but some of that energy will be bounced right
back and can either cause interference or even damage to your radar's
receiver. All the more reason not to use a 4 kw system.


Nope, not even close to being true. The radar receiver has a Range Gate
built into the frontend that does not enable the receiver to see
anything untill after the transmitted pulse has long since left the
antenna. The Range Gate timing is what sets the Minimum Radar Range
of the radar and is usually set so that the minimum range is on the
order of 50 or 75 yards. Any reflected Transmitter Pulse will have long
since traveled out to the mast or reflective surface aboard the same
vessel and returned long before the Range Gate opened up the receiver
frontend, looking for a return signal.
Your thinking of the Second Generation Radars with RadioActive TR Cells,
that when hear the end of their useful life just opened up and allowed
the Transmitter Pulse to reach the Microwave Diode Crystals, and destroy
them. All third generation and later radars, use a different Range Gate
System, and are not subject to this type of problem. Any return signal
from farther than 75 yards will be so attenuated in power density, that
it can't hurt the receiver frontend. Inverse Square Law prevails in the
RF World. Now the above is all well and good, but does not take in to
account that when rafted up to another vessel which is operating it's
Radar and your radar is operating as well, and the two antenna's point
exactly at each other for a few cycles of their transmitters, that
damage couldn't happen to the recivers from the others transmitter.
the probubility of this is low, but still significant. Never allow
a rafted vessel to operate a radar, when your antenna is pointed toward
theirs.


Bruce in alaska
--
add a 2 before @

Me February 15th 05 08:49 PM

In article ,
Jeff Morris wrote:

renewontime dot com wrote:
Thanks for the clarifications, guys. So, to sum up, if you have a
mizzen, it's a great spot for a radar with little downside unless you
think you need the height of the mainmast, but then you may foul an
overlapping genoa.

Does that sum it up?



Just remember that a radar sends out radio waves, and any metal in front
of it will cause part of your radar signal to be bounced back to your
radar. The metal mast and rigging may not obscure your radar display
(an empty "shadow area"), but some of that energy will be bounced right
back and can either cause interference or even damage to your radar's
receiver. All the more reason not to use a 4 kw system.


What??? Are you claiming its dangerous to mount a radar on the mast?
Actually, most masts will reflect the energy away. RayMarine advises to
put a block of wood between the mast and dome if there's interference on
the screen, but I've had several (including a large Nonsuch mast) and
never seen a problem. I don't see how there would be a problem with the
main mast interfering with a mizzen mounted dome.


Naw, don't worry about such stuff, it is not factual information anyway.


Read Meinhert, and Bruce in alaska's posts for the FACTS.......


Me

otnmbrd February 15th 05 09:24 PM


"Bruce in Alaska" wrote in message news:

OTN, the Horozontal Beamwidth of your Commercial Maritime Radar is
significantly smaller than that of the units found on most Pleasure
type vessels. That makes a HUGH difference in the Target Discrimination
Ability between the two radars. Apples and Oranges, here.......


Bruced in alaska



This I understand. However, and here I need to be careful to note that my
comments are not technical, rather, practical experience based, dating back
to Decca 101's and KH 17's , on multiple size/type vessels ...... I've
rarely experienced a serious problem with close aboard, lost targets that
would negatively impact the navigational procedure I was using, including
docking.
Admittedly, some units were better than others, either due to the basic unit
and/or it's condition and you needed to adjust some procedures, but, my
point is that you don't want to consider a radar's use "drop dead useless"
below a certain range, based on pure technical data, without first checking
your particular unit under real conditions to see if they apply or are
indeed a problem.

MOFWIW

otn



[email protected] February 16th 05 06:52 PM

I'm looking at a sailboat that has a "Vigil RM radar".
As it works and I have other things I will need
to spend money on up front, it will be well down
on my list of items to replace. In the meantime
I will have to live and work with it.

Can anyone give me some info on what these were like
in construction and quality? Appears to be over 10 yrs old,
with crt display, and 24" radome.

Thanks


Bruce in Alaska February 16th 05 10:20 PM

In article et,
"otnmbrd" wrote:

This I understand. However, and here I need to be careful to note that my
comments are not technical, rather, practical experience based, dating back
to Decca 101's and KH 17's , on multiple size/type vessels ...... I've
rarely experienced a serious problem with close aboard, lost targets that
would negatively impact the navigational procedure I was using, including
docking.
Admittedly, some units were better than others, either due to the basic unit
and/or it's condition and you needed to adjust some procedures, but, my
point is that you don't want to consider a radar's use "drop dead useless"
below a certain range, based on pure technical data, without first checking
your particular unit under real conditions to see if they apply or are
indeed a problem.

MOFWIW

otn


Yep, I'll go along with that......


Bruce in alaska
--
add a 2 before @

Roger Derby February 16th 05 10:58 PM

Think "watt-seconds".

2000 watts for 2 microseconds requires 4 watt-milliseconds or 0.004
watt-seconds. Throw in the PRF, and the rest is heat.

Roger

http://derbyrm.mystarband.net/default.htm

"Larry W4CSC" wrote in message
...

snip

Isn't it amazing how 2,000 watts of peak RF power just appears from thin
air for only 1-2 watts more DC? Magic? Divine intervention? Maybe its
the printer stepper motor that turns the rubber band that drives the PC
board antenna array...??





rhys February 17th 05 04:14 AM

On Tue, 15 Feb 2005 15:59:52 GMT, wrote:

On Tue, 15 Feb 2005 10:20:41 -0500, rhys wrote:

I wonder, however, if my "armature idea" would be useful for any
similar devices, as opposed to a "hard-mount" at the wheel? If, for
instance, you had a 15" LCD panel and a wireless mouse, the panel
could be some distance away and still be readable.

R.


http://www.ram-mount.com/index.htm


Oh, gracious...what a selection! Thanks, BB!

R.

rhys February 17th 05 04:19 AM

On Tue, 15 Feb 2005 11:34:15 -0500, Jeff Morris
wrote:

However, once you get used to
have the controls at the helm, its hard to see how you can properly use
a radar that isn't nearby.


As I said, my current boat is tiller-steered, so I am only arm's
length from the mainsheet traveller *forward* of the hatch, never mind
the companionway itself. Reaching for anything and steering involves
using my knees and leaning. If I use the tiller extender, I can go
into the galley and get a refreshing beverage, or lash it in place and
go forward to handle sails. It's not a small boat, either...nearly 34
feet.

Makes me wonder why tillers haven't stayed popular, except that I know
if's because socializing in the cockpit trumps steering.

But that's another topic, perhaps.

R.


rhys February 17th 05 04:20 AM

On Tue, 15 Feb 2005 20:35:24 GMT, Dan Best
wrote:

I have two singout arms in my hatchway. The raday display is on one and
a gps/fish finder is on the other. Unfortunately, there just wasn't
quite enough room to attach both devices to just one arm, my hatch just
isn't tall enough to have them one above the other. When both are
deployed so the helmsman can see them, it's a little inconvienient since
to in or out of the hatch, you have to either carefully step over them
or swing one of them out of the way. In reality, this is not a big deal
since the radar is only rarely used (but when we do use it, we are
REALLY glad we have it).


Exactly. Would love to see pictures and how you routed the power and
other cables to (presumably) the nav station/DC panel.

R.


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