Radar vs GPS/Sounder
 

On Mon, 24 Nov 2003 20:30:38 GMT, Bruce in Alaska
wrote (with possible editing):

In article ,
"Jeff Morris" wrote:

I often keep it in standby to save power and
magnetron time (they do wear out)

Just a point of note here. Leaving the radar in standby on most
civilian consumer radars does not save anything on Magnitron
Time. What wears out is the Filiment (heater) and that is
always ON whenever the Powersupply is on, even in Standby Mode.
To convise yourself of this, do this simple test. When you first
"Fire up" your radar, there is a timer that allows the Magnitron
to "Heat up and Stabalize", usually for three (3) minutes or so.
After that initial "Warm up Period", when going from "Standby"
to "Operate" does your radar require another "Warm up Period"?
If so, then you are correct on your Magnitron time statement.(Not very
likely to be this way) If not, then then "Standby" only save you
Transmit Power, and that's not really very much in most cases.
Most modern Magnitrons have between 2000 and 4000 hours of Service
Life and that is Filiment Life, really.

Bruce in alaska

No flame, Bruce, but what normally wears out a magnetron is depletion
of the cathode. The cathode is heated by the filament so that it will
emit electrons. As the tube ages, its ability to emit them decreases.
As radar operates in pulsed service, the tubes should last a good deal
longer. Often, a magnetron which is substantially dead, will still
"light up" just like the final output tubes in transmitters.
--

Larry
Email to rapp at lmr dot com

Radar vs GPS/Sounder
 

On Sun, 23 Nov 2003 09:07:50 -0800, "Lloyd Sumpter"
wrote:

Hi,

Thinking of getting radar for Far Cove, mainly for this planned trip to WCVI,
which has lots of fog.

Now, I've survived 20+ years of sailing Georgia Strait, etc. without radar.
If it's really foggy, I just stay put. If I venture out, I use several nav aids
including GPS to determine my position, blow my horn and listen.

I'm thinking that, even WITH radar, I wouldn't venture out in unfamiliar
waters in dense fog. And if I was out and the fog rolled in on me, I would think
that GPS, sounder and a good chart would be better to find that anchorage than
radar, assuming I could see at least 100 ft or so.

Under ideal conditions, you are correct. The benefit of radar,
however, is that you can see what you can't hear, i.e. other shipping
that has no intention of letting a little fog screw with the
schedule...

Also, to a lesser extent, you become visible to other shipping in a
way that a horn can't: precisely.

Finally, you can use a radar to get bearings on shore objects at night
if the GPS conks out and it's too cloudy to use celestial...which I
notice you didn't mention...G

I would say radar, sensibly used, complements but doesn't replace
paper, GPS, depth sounders, horns and good old seamanship. While it is
possible to get swamped with "too much information", particularly if
it doesn't agree, too little information is often what proves fatal to
the boat.

Comments?

Also, if I mount the radome on a post at the stern like most seem to, doesn't
the mast and sail interfere with it looking forward?

Yes, but barely, or at least not as much as you'd think. You can
offset the radome on a pole and gimbal off a stern quarter if you
wish, and then the "blind spot" would be 10 deg. port or starboard
looking forward.

I agree, a gimbal mount at the cross-trees is probably ideal, however,
but it's easier to get at stuff on a pole. Probably the nicest option
is an arch with the radar offset and a way to lash the boom, hang
bimini canvas, affix a GPS, VHF, etc., and yet keep all within easy
reach.

R.

Lloyd Sumpter
"Far Cove" Catalina 36

Radar vs GPS/Sounder
 

On Sun, 23 Nov 2003 09:07:50 -0800, "Lloyd Sumpter"
wrote:

Hi,

Thinking of getting radar for Far Cove, mainly for this planned trip to WCVI,
which has lots of fog.

Now, I've survived 20+ years of sailing Georgia Strait, etc. without radar.
If it's really foggy, I just stay put. If I venture out, I use several nav aids
including GPS to determine my position, blow my horn and listen.

I'm thinking that, even WITH radar, I wouldn't venture out in unfamiliar
waters in dense fog. And if I was out and the fog rolled in on me, I would think
that GPS, sounder and a good chart would be better to find that anchorage than
radar, assuming I could see at least 100 ft or so.

Under ideal conditions, you are correct. The benefit of radar,
however, is that you can see what you can't hear, i.e. other shipping
that has no intention of letting a little fog screw with the
schedule...

Also, to a lesser extent, you become visible to other shipping in a
way that a horn can't: precisely.

Finally, you can use a radar to get bearings on shore objects at night
if the GPS conks out and it's too cloudy to use celestial...which I
notice you didn't mention...G

I would say radar, sensibly used, complements but doesn't replace
paper, GPS, depth sounders, horns and good old seamanship. While it is
possible to get swamped with "too much information", particularly if
it doesn't agree, too little information is often what proves fatal to
the boat.

Comments?

Also, if I mount the radome on a post at the stern like most seem to, doesn't
the mast and sail interfere with it looking forward?

Yes, but barely, or at least not as much as you'd think. You can
offset the radome on a pole and gimbal off a stern quarter if you
wish, and then the "blind spot" would be 10 deg. port or starboard
looking forward.

I agree, a gimbal mount at the cross-trees is probably ideal, however,
but it's easier to get at stuff on a pole. Probably the nicest option
is an arch with the radar offset and a way to lash the boom, hang
bimini canvas, affix a GPS, VHF, etc., and yet keep all within easy
reach.

R.

Lloyd Sumpter
"Far Cove" Catalina 36

Radar vs GPS/Sounder
 

On Mon, 24 Nov 2003 06:51:32 -0800, "Lloyd Sumpter"
wrote:


Final question: if the fog was thick (vis. maybe 100 ft) and you had radar (and
GPS, etc) would you go out?
If I thought there was clearer weather off shore, or at my
destination, or if I knew the waters and needed nav practice (like
shooting sun sights up through a hole in the fog!), sure I would. If
the fog is close to shore and you see 90% of your city/town rising out
of a solid bank, it's well worth that first mile of damp sailing to
get offshore a bit and look back.

Finally, particularly in summer, fog burns off. If you leave at 8 A.M.
and the fog's gone by 10:30 A.M., you are already well into your day's
cruising, and you'll have tons of searoom over the folks who waited
"until it clears up".

R.

Radar vs GPS/Sounder
 

On Mon, 24 Nov 2003 06:51:32 -0800, "Lloyd Sumpter"
wrote:


Final question: if the fog was thick (vis. maybe 100 ft) and you had radar (and
GPS, etc) would you go out?
If I thought there was clearer weather off shore, or at my
destination, or if I knew the waters and needed nav practice (like
shooting sun sights up through a hole in the fog!), sure I would. If
the fog is close to shore and you see 90% of your city/town rising out
of a solid bank, it's well worth that first mile of damp sailing to
get offshore a bit and look back.

Finally, particularly in summer, fog burns off. If you leave at 8 A.M.
and the fog's gone by 10:30 A.M., you are already well into your day's
cruising, and you'll have tons of searoom over the folks who waited
"until it clears up".

R.

Radar vs GPS/Sounder
 

On Tue, 25 Nov 2003 09:50:07 -0500, DSK wrote:



Our radar has proven to be a really good tool for use in marginal visibility and for
tracking ship traffic. When we first bought the boat I was not convinced of it's
usefulness, especially not that particular set. But now it works great.


One last thing I forgot to mention: Here on Lake Ontario many summer
storms appear as "pop-up" cumulonimbus thunderheads, with 50-60 knot
line squalls that can lay you flat if you have, as most do most of the
time, a full hoist...

There's only 20-30 miles to the west end of the lake here (Toronto)
and squalls that develop at that end (south to west, usually) can get
here in minutes.

A properly tuned radar will show squall lines quite sharply. If its
blasting at you at 48 knots and you catch it on radar aft at 12 NM,
you can shorten sail in a timely fashion and ride out an otherwise
very unpleasant, possibly expensive and potentially dangerous 15
minute surfing session.

And of course, if you can see rain bands, you can sail between them,
if the wind and waves allow.

R.

Radar vs GPS/Sounder
 

On Tue, 25 Nov 2003 09:50:07 -0500, DSK wrote:



Our radar has proven to be a really good tool for use in marginal visibility and for
tracking ship traffic. When we first bought the boat I was not convinced of it's
usefulness, especially not that particular set. But now it works great.


One last thing I forgot to mention: Here on Lake Ontario many summer
storms appear as "pop-up" cumulonimbus thunderheads, with 50-60 knot
line squalls that can lay you flat if you have, as most do most of the
time, a full hoist...

There's only 20-30 miles to the west end of the lake here (Toronto)
and squalls that develop at that end (south to west, usually) can get
here in minutes.

A properly tuned radar will show squall lines quite sharply. If its
blasting at you at 48 knots and you catch it on radar aft at 12 NM,
you can shorten sail in a timely fashion and ride out an otherwise
very unpleasant, possibly expensive and potentially dangerous 15
minute surfing session.

And of course, if you can see rain bands, you can sail between them,
if the wind and waves allow.

R.

Radar vs GPS/Sounder
 

wrote in message
...
...
Also, to a lesser extent, you become visible to other shipping in a
way that a horn can't: precisely.


This is a point I've wondered about: it seems that vessels with active radar
appear on my radar with a large arc centered on the vessel's blip. I've assumed
this is an interaction between their radar and mine. Does this also mean that
my radar also enhances my picture on their screen?

-jeff

Radar vs GPS/Sounder
 

wrote in message
...
...
Also, to a lesser extent, you become visible to other shipping in a
way that a horn can't: precisely.


This is a point I've wondered about: it seems that vessels with active radar
appear on my radar with a large arc centered on the vessel's blip. I've assumed
this is an interaction between their radar and mine. Does this also mean that
my radar also enhances my picture on their screen?

-jeff

Radar vs GPS/Sounder
 

On Tue, 25 Nov 2003 21:42:50 -0500, "Jeff Morris"
wrote:

wrote in message
.. .
...
Also, to a lesser extent, you become visible to other shipping in a
way that a horn can't: precisely.


This is a point I've wondered about: it seems that vessels with active radar
appear on my radar with a large arc centered on the vessel's blip. I've assumed
this is an interaction between their radar and mine. Does this also mean that
my radar also enhances my picture on their screen?

-jeff




Don't count on it. The arc that you see from the other guys radar is
from interference from his transmitter. Your radar is picking up your
transmitters echo and his transmitter directly. His pulses are not
synchronized with yours so you see the trail of pulses from his
transmitter while your transmitter is between pulses. It will give
neither of you any indication of where the other is.

This only happens if the two transmitters are very close to the same
frequency. Even though the two radar's may be exactly the same type of
radar, they may or may not be close enough to the same frequency. The
magnetrons are all tuned slightly different and drift somewhat.

On most radar's there is also an interference filter on the receivers
that eliminate or reduce that type of interference.

Then too the other ship may be using a radar in a completely different
band. No interference to either of you.

Regards
Gary