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Old 18 April 2006, 15:14   #61
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Its mounted upright currently, not sure the 4m pole will be possible though
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Old 19 April 2006, 04:30   #62
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Quote:
Originally Posted by codprawn
....Peak pulses may look good on paper but in the real world don't mean so much.
As usual I think you’ve missed the point, sure tri lens has a nice smooth reflection but it is only painting an area 5mtrs square, whereas the Echomax paints a 20mtrs square, albeit with some peeks and nulls. Would you rather present a large but rough image as apposed to a small but well formed one
As always you are arguing in circles, on the one hand you rave about Seame because of the size of its (rough)image now you are saying that small but well formed is better more Cobbledygook Des
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Old 19 April 2006, 05:50   #63
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Quote:
Originally Posted by Scary Des
Would you rather present a large but rough image as apposed to a small but well formed one
As always you are arguing in circles, on the one hand you rave about Seame because of the size of its (rough)image now you are saying that small but well formed is better more Cobbledygook Des
Are you still confused about this, Des? The strength of the return does not determine the size if the image on the screen. It will determine the distance at which the object can be seen and also the brightness/clarity of the image on the screen. But if the return is solid, since the screen has a limited brightness, this is the level at which it will show.

Codders is correct. It is a compromise. Would you rather be seen for some of the time at a greater distance or at only some angles or for all of the time at a limited distance?

I would be concerned about a reflector which had nulls for a good few degrees of arc however, you can have a reflector where the plot is spikey but the lows are still quite acceptable.

I remember reading the article that Cod is talking about and it did seem resonably well carried out but, on the few occasions I've relied on magazine articles for making a decision, I regretted it each time. You need to live with something for a while to appreciate which of it's characteristics are important to you. Often, it's the subtleties that make the thing nice to own and use.
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Old 19 April 2006, 06:07   #64
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Quote:
Originally Posted by Scary Des
.... Would you rather present a large but rough image as apposed to a small but well formed one ....
Some of us don't have a choice in this life.....
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Old 19 April 2006, 07:19   #65
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Some of us don't have a choice in this life.....
Trust you....



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Old 19 April 2006, 09:12   #66
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Quote:
Originally Posted by Scary Des
As usual I think you’ve missed the point, sure tri lens has a nice smooth reflection but it is only painting an area 5mtrs square, whereas the Echomax paints a 20mtrs square, albeit with some peeks and nulls. Would you rather present a large but rough image as apposed to a small but well formed one
As always you are arguing in circles, on the one hand you rave about Seame because of the size of its (rough)image now you are saying that small but well formed is better more Cobbledygook Des
Try to think of it as a laser beam verses a flourescent lamp. The flouro lamp may be a lot dimmer but it is visible FAR more of the time - the laser beam will give a MASSIVE burst but only for a fraction of the time.

2 extremes I know but trying to illustrate a point!!!
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Old 19 April 2006, 13:48   #67
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Originally Posted by jwalker
Are you still confused about this, Des? The strength of the return does not determine the size if the image on the screen. ......
Quote:
Originally Posted by raymarine e series manual
On-screen targets may be large, small, bright or faint, dependent on the size of the object, its orientation and surface. Strongest target returns are displayed in yellow with weaker returns in two shades of blue. Be aware that the size of a target on screen is dependent on many factors and may not necessarily be proportional to its physical size. Nearby objects may appear to be the same size as a distant larger objects.
With experience, the approximate size of different objects can be determined by the relative size and brightness of the echoes.
You should bear in mind that:
The size of each on-screen target is affected by:
The physical size of the reflecting object.
The material from which the object is made. Metallic surfaces reflect signals better than non-metallic......
this is what Raymarine say about there radar, does yours work differently Des
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Old 19 April 2006, 14:05   #68
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Originally Posted by codprawn
Try to think of it as a laser beam verses a flourescent lamp...........
No, try to think of it as a big return so people can see you or a small return which they won’t If you look at DJL's post (47) you will see that the tri-lens is achieving 4mtr2 at best whereas the echomax is achieving 5mtr2 at worst and 20mtr2 at best Simple choice. Des
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Old 19 April 2006, 14:33   #69
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Quote:
Originally Posted by Scary Des
No, try to think of it as a big return so people can see you or a small return which they won’t If you look at DJL's post (47) you will see that the tri-lens is achieving 4mtr2 at best whereas the echomax is achieving 5mtr2 at worst and 20mtr2 at best Simple choice. Des
It is NOT that simple!!!

Imagine someone in the water with a chemical lightstick and someone with a laser.

IF the laser happens to shine straight into your eyes then fine you can't miss them - on the other hand the light stick is nowhere near as bright but is visible far more often!!!
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Old 19 April 2006, 15:53   #70
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Quote:
The size of each on-screen target is affected by:
The physical size of the reflecting object.
The material from which the object is made. Metallic surfaces reflect signals better than non-metallic......
Quote:
Originally Posted by Scary Des
this is what Raymarine say about there radar, does yours work differently Des
Nope, mine works just like that.

Please note,
Quote:
The size of each on-screen target is affected by the physical size of the reflecting object.
So, a radar reflector, which is likely to be in the region of 300-400mm across, is never going to look like a tanker on the radar screen.

Also please note,
Quote:
The material from which the object is made. Metallic surfaces reflect signals better than non-metallic.
This indicates that a metallic object is more likely to represent its approximate horizontal length than, say, a rib because of the likelyhood of the rib not returning a sufficient echo over its whole length. It does not imply that a metallic object will in some way amplify the return.

Lets consider the case of, for example, a sheet of metal 50mtrs long my 1 metre wide. I'm going to ignore the fact that it is flat and therefore some of the radar energy will not return.

If the sheet was standing on end, it would give a return which represented 1mtr wide. If it was on its side, it would give a return which represented 50mtrs wide.

In both cases, the return would contain errors because of the radar beam width. The amount of error would depend upon the radar in question.

As your quote indicates, there is a degree of learning necessary to interpret a radar screen. Particularly, but not entirely, because irregular shapes will modify the returns. However, it's not overly difficult to get to grips with.
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