Radar reflectors

[Daydream believer]

I have 2 Plastimo 100 diameter reflectors
Now these get poor revues in magazine tests
I have these mounted on my mid shrouds just under the second spreaders
My theory being that being angled they would give a better reading when the boat is heeled as they splay in on the line of the shrouds
I had occasion to be attended by Eyemouth lifeboat in heavy weather& the coxwain made particular comment on how strong my radar signal return was.
I said that this was because they had good gear but he actually said their electrics were due for renewal as it was out of date so this was not the reason
A friend knew someone involved in military radar. He commented on this so the military chap ran a computer programme over this for fun
His comment was surprising in that it appears 2 reflectors mounted one above the other are best ( mine are the same level but opp sides & angles). They actually give a better return more than the sum of the 2. Ie not twice the signal but more like 6 times the reflection

Must be worth PBO looking into this

 

[Rigger Mortice]

I'm surprised that nobody has replied to your post........

Perhaps you should get your contect to send those results to PBO?

I must admit that I'm surprised; those reflectors had a very poor review when MAIB commissioned tests following the loss of "Ouzo". The individual reflectors are only dihedral rather than the usual trihedral corner cube variety.

 

[CAPTAIN FANTASTIC]

You need to follow it up; if you are correct, then many people including me, will be delighted, because it is simple, low cost and easy way to be seen.

 

[VicS]

Also very surprised

In their report Qinetiq say, "The 4” tube reflector performed very poorly" and "The 4” tube reflector is not considered suitable due to its poor performance. It is also recommended that the 2” tube reflector is not suitable since the performance of this target will be even lower."

 

[mjcoon]

...
His comment was surprising in that it appears 2 reflectors mounted one above the other are best ( mine are the same level but opp sides & angles). They actually give a better return more than the sum of the 2. Ie not twice the signal but more like 6 times the reflection.

It doesn't sound like good physics to me; more like energy from nothing = perpetual motion!

Mike.

 

[Daydream believer]

It doesn't sound like good physics to me; more like energy from nothing = perpetual motion!

Mike.

It first sounded that way to me. But the point that does come from my episode is that the coxswain went out of his way to tell me what a good echo my reflectors had. That is fact, not suposition
Of course it could have been fluke weather conditions
I posted the thread to see of anyone could support the findings

 

[bedouin]

Doesn't sound likely to me - you can't change the laws of physics.

A single observation of a good reflection doesn't tell you much - a radar reflector needs to produce a good return at all angles.

 

[macd]

the coxswain went out of his way to tell me what a good echo my reflectors had. That is fact, not suposition

How can either of you be so sure? The only way to check whether the reflectors, rather than the rest of the boat or its hole in the water, were causing the strong echo would be to take them off and try again.

 

[Daydream believer]

How can either of you be so sure? The only way to check whether the reflectors, rather than the rest of the boat or its hole in the water, were causing the strong echo would be to take them off and try again.

I was running under bare poles at 5.5 kts so i would have thought only the mast could be helping the return echo
Do masts add much?

 

[macd]

I was running under bare poles at 5.5 kts so i would have thought only the mast could be helping the return echo.

Why would bare poles make any difference? Dacron isn't a reflector. Your mast (if metal) will reflect, so will sundry other surfaces, plus the hole in the water made by your boat. Attributing the strong return so categorically to your reflectors simply isn't supported by the evidence you offer. You may be right, you may not: we just don't know.

 

[Rigger Mortice]

It could simply be that one of the reflectors happened to be at the correct angle to give the optimal return. Certainly the MAIB results suggest that when the Plastimo reflector is "correctly" oriented it gives a good result.

 

[lw395]

It could simply be that one of the reflectors happened to be at the correct angle to give the optimal return. Certainly the MAIB results suggest that when the Plastimo reflector is "correctly" oriented it gives a good result.

This is true, they work well for upright posts.
That is also true of the bare mast.
But, in actual operation, the absolute level of return is often not the problem, it is the level relative to the sea clutter.
On flat water, or where the wave pattern is not reflecting toward the radar, a mediocre return could look brilliant.

The can be a lot of truth in stacking reflective elements being effective. If done right, it not only catches more energy, but also reflects it back in a tighter beam. That's good if it's in the right direction, bad otherwise.

 

[mjcoon]

The can be a lot of truth in stacking reflective elements being effective. If done right, it not only catches more energy, but also reflects it back in a tighter beam. That's good if it's in the right direction, bad otherwise.

Increasing the aperture of any optics can make the beam tighter. But I don't understand how adding duplicate units could do that. Got any references?

Mike.

 

[lw395]

Increasing the aperture of any optics can make the beam tighter. But I don't understand how adding duplicate units could do that. Got any references?

Mike.

Kraus is the default text book on antennas.
Or try Skolnik on Radar Systems.
Modern fighter air craft and ship radars are often phased array, i.e. stacks of elements in one or two dimensions.
You are close to the money with optics, it's the same theta=lambda over d malarkey as a lens.
It's why radars with wider scanners have better angular resolution.
It's a big subject full of hard sums, I have been on the fringes of it, but I'm not really an antenna person.