Passive radar reflector - anything better than Echomax?

[Refueler]

I suspect that accelerometers are doing the driving so what you have is much the same chip as is in your phone. More or less a development from the inertial platform navigation systems used in long distance aircraft from the 60s on

Don't get me started on INS ... my Father was involved in CAA / BOAC testing. When I went to sea - the discussions we had comparing marine to air nav and systems would write books ..

As to Accelerometers - we now have boards that are size of your thumbnail containing 6 axis computation and stability for our drones and models. Basically 3 solid state gyros + 3 solid state accelerometers.

 

[Roberto]

Echomax do one too. I prefer the dual band X and S version as ships carry both radars. I also carry a large rain catcher and an old Echomax passive reflector.

I have the X-S Echomax, it has two coloured led indicating the type of radar frequency being received (and reflected by the device), one green led for X band and amber led for S-Band.
While offshore, when a ship passes into range it's almost always the amber led which flickers; along the coast mostly the green one, or the amber one while in range of terrestrial signal stations.

 

[Bobc]

Wouldn't actual events be worthy of note ?

This boat in middle of Baltic in F4 - 5 moderate seas with no reflector was plotted on a ships ACAS at over 10nm ...

This boat, fitted with a big Echomax reflector was not visible on radar to a container ship in the English Channel which was less than 2 miles away and on a collision course. I know this because I called them up to ask if they could see me.

 

[Refueler]

Bobc ... appreciated your post ...

Now what weather ? and other factors ?

I believe you - but it does sound as though OOW was not good at radar setup .. or some other factor ?

 

[Refueler]

I have the X-S Echomax, it has two coloured led indicating the type of radar frequency being received (and reflected by the device), one green led for X band and amber led for S-Band.
While offshore, when a ship passes into range it's almost always the amber led which flickers; along the coast mostly the green one, or the amber one while in range of terrestrial signal stations.

Dunno about others here and what they will say ... but when I was OOW .... we looked upon 3cm as detailed but more subject to clutter and sea state. The 10cm as less detail and less subject to clutter and sea state.
There was talk in early days that 3cm was preferred by Brits / European .... 10cm preferred by US .. I know that back in the 70's I did sail on the odd older Brit ships that had two 3cm radars and no 10cm.
But later near all had both 3 and 10.

One aspect that suffered with this .. example :

LNG carrier running Brunei to Japan .... early days of Transit Satnav ... many of you will not have seen that ... it was awful !! We were test bed for Magnavox machines .. The sats over about 10 days would bunch up and Palawan Passage - South China Sea was particularly bad for it ... and you would have a series of positions one after another in short space of time ... then they'd start spacing out again .. and then 10 days later bunched up again .. unlike GPS - it was not position on demand.
So Palawan Passage .. 85,000 cu.m of highly flammable LNG .... with all the shoals and wrecks dotted about.
The vessels had two radars (this was before ACAS and ECDIS) .... one 3cm and one 10cm. Some bright spark had taken the old idea of interswitched radar antennas and fitted us with it. So idea was going UP loaded - we would have 3cm on the port antenna to catch targets to port .. 10cm on stbd antenna to catch land targets .... on ballast passage coming down other way - we'd switch them over .... The antennas had shadow sectors created by the mast between them.
Trouble was the idiot had ignored fact that 3cm used waveguide and xxx size antenna .. 10cm used cable and different size antenna.
But we duly did as told and logged the antenna config etc.

Now here's one for you - those same ships - we had a mark we used to alter course on ... it was a wreck and shoal that was depicted sharply on the echo-sounder ... the ship was on liner run .. so we had all the marks / key features noted so well - we could navigate literally blind. We would have the Echo Sounder plotter running switched to bow sensor ... watch the pens and as soon as it shot across the paper - turn the ship to next course. Never failed !

Apologise for thread drift ... getting old and memories come flooding back !

 

[Bobc]

Bobc ... appreciated your post ...

Now what weather ? and other factors ?

I believe you - but it does sound as though OOW was not good at radar setup .. or some other factor ?

About F3-4, flat-ish water, thick fog.

The ship was on my rear quarter, so I suspect the reflector was largely hidden by the mast. Still worrying that his radar didn't pick up a 50fter less than 2 miles away. I actually had to ask him to alter course for me.

 

[Refueler]

About F3-4, flat-ish water, thick fog.

The ship was on my rear quarter, so I suspect the reflector was largely hidden by the mast. Still worrying that his radar didn't pick up a 50fter less than 2 miles away. I actually had to ask him to alter course for me.

Yes - I would be seriously concerned ....

But you do qualify it now by saying thick fog. Fog is like rain - it can easily blanket out even good RCS targets ... being water in the air. If the OOW has altered the clutter / gain to supposedly compensate for fog - then he could easily adjust out your target return.

Its why radar instructors when I did my tickets advised us to frequently change gain in rain / fog conditions to check we were not filtering out targets.

OK another point to consider ... was it a large Container vessel with full stack on deck ? You say coming up behind ? Some container vessels have added remote antenna fwd to solve the line of sight problem the container stack creates. 2nm may have been too close if he did not have that remote antenna .... 2nm to you is a lot ... but to him is CLOSE !! maybe too close for radar sight line to see. Just thinking out loud.

 

[James_Calvert]

Interesting point about the reflector being shielded by the mast.

We dangle ours when we need to on a signal halyard from the crosstrees.

Guess that makes it less likely to be shielded...

 

[Refueler]

Interesting point about the reflector being shielded by the mast.

We dangle ours when we need to on a signal halyard from the crosstrees.

Guess that makes it less likely to be shielded...

Surely then the mast is shielding the reflector to one side ?

 

[Bobc]

Yes - I would be seriously concerned ....

But you do qualify it now by saying thick fog. Fog is like rain - it can easily blanket out even good RCS targets ... being water in the air. If the OOW has altered the clutter / gain to supposedly compensate for fog - then he could easily adjust out your target return.

Its why radar instructors when I did my tickets advised us to frequently change gain in rain / fog conditions to check we were not filtering out targets.

OK another point to consider ... was it a large Container vessel with full stack on deck ? You say coming up behind ? Some container vessels have added remote antenna fwd to solve the line of sight problem the container stack creates. 2nm may have been too close if he did not have that remote antenna .... 2nm to you is a lot ... but to him is CLOSE !! maybe too close for radar sight line to see. Just thinking out loud.

No idea about the load etc., as I never saw it (passed about 1/2 mile across our stern.

Surely the whole point of radar and radar reflectors is that they are for when No.1 Eyeball is no good, so it's a bit rubbish if they don't work in fog, which is when you need them.

Anyway, I have now replaced the AIS receiver with a transponder, so they'll be able to see me now.

 

[RobbieW]

so they'll be able to see me now

With the caveat 'if they are looking'

 

[AntarcticPilot]

.... early days of Transit Satnav ... many of you will not have seen that ... it was awful

Not merely seen, but used in anger! First (about 1975) was on a seismic survey vessel in the North Sea - a big setup, the size of a filing cabinet - probably an early Magnavox system. It was amazing to see fixes come in at better than 50m accuracy! Then in 1983, I procured a yacht system that we used in the Arctic; in that case it was a static system, so we set it on averaging mode and got positions down to a few metres. Finally, the major survey network for the Antarctic Peninsula was fixed to Transit fixes.

The system in the seismic vessel was linked to a sort of dead-reckoning system, and the track plotted on a paper chart. It was always interesting to see the sudden glitches when a Transit fix came in!

 

[Graham376]

Visited the bridge of Stena Explorer 40kt ferry on trip from Holyhead to Ireland. I asked skipper what speed they slow down to in fog and he replied they don't, they have a timetable. When asked about yachts and small boats on radar, he said they saw those with reflectors at about 8 miles but those without, often too close for comfort and likely impossible to avoid in fog. I'll keep my Echomax

 

[Refueler]

Not merely seen, but used in anger! First (about 1975) was on a seismic survey vessel in the North Sea - a big setup, the size of a filing cabinet - probably an early Magnavox system. It was amazing to see fixes come in at better than 50m accuracy! Then in 1983, I procured a yacht system that we used in the Arctic; in that case it was a static system, so we set it on averaging mode and got positions down to a few metres. Finally, the major survey network for the Antarctic Peninsula was fixed to Transit fixes.

The system in the seismic vessel was linked to a sort of dead-reckoning system, and the track plotted on a paper chart. It was always interesting to see the sudden glitches when a Transit fix came in!

Yep .. first test systems we had were : Big box about size of large filing cabinet in the corner of Wheelhouse feeding to a smaller box at end of chart table - then to a TV like display.
That then got changed to the all in one TV like Magnavox unit ....

Both ran DR positioning till a Transit came in ...

I worked with Compagnie Generale de Geophysique (CGG) out of Massy (Paris) France for while ... they developed Syledis system ... we were Seismic boats - converted stern trawlers and minesweepers. Dragging 3 mile cables around.
Syledis was amazing ... far better than the Loran and other Western Geo and so were using ... Syledis transponders were placed on rig towers .. on spot height locations ashore ... it was short range - but so accurate - we could tell when the Rig skidded the tower ...

We also had Steam cannons - much cleaner 'shot' than air ...

Memories !!

 

[Slowboat35]

Fog blocks radar? Really? Airborne weather radar - 3cm x band sees rain only, no way is it affected by cloud (aka fog) as the droplets are far far too small to reflect - clearly it would be useless if it did.
I very very much doubt there is any adverse effect on x band radar by fog.

 

[AntarcticPilot]

Yep .. first test systems we had were : Big box about size of large filing cabinet in the corner of Wheelhouse feeding to a smaller box at end of chart table - then to a TV like display.
That then got changed to the all in one TV like Magnavox unit ....

Both ran DR positioning till a Transit came in ...

I worked with Compagnie Generale de Geophysique (CGG) out of Massy (Paris) France for while ... they developed Syledis system ... we were Seismic boats - converted stern trawlers and minesweepers. Dragging 3 mile cables around.
Syledis was amazing ... far better than the Loran and other Western Geo and so were using ... Syledis transponders were placed on rig towers .. on spot height locations ashore ... it was short range - but so accurate - we could tell when the Rig skidded the tower ...

We also had Steam cannons - much cleaner 'shot' than air ...

Memories !!

I was with S&A Geophysical, which became Horizon Exploration. The vessel was "Oil Hunter"; a converted stern trawler. I still have sharp memories of retrieving the cable while waves were washing up the stern shute! Trisponder systems were the gold standard for position fixing at the time; again, I used such a system in 1983 (Motorola, I think); the Transit system was used to fix two of the base stations.

 

[Bobc]

With the caveat 'if they are looking'

Well exactly. I always work on the premise that nobody else can see you and never assume they can.

 

[Graham376]

Fog blocks radar? Really? Airborne weather radar - 3cm x band sees rain only, no way is it affected by cloud (aka fog) as the droplets are far far too small to reflect - clearly it would be useless if it did.
I very very much doubt there is any adverse effect on x band radar by fog.

Could be that maximum range is reduced but I'm rarely on that so haven't noticed. What I have noticed though is when it's a very wet drizzly fog, danbuoys and other small targets show up better.

 

[C08]

Active reflector's are good.
Passive reflector's are less good, but still give a better feeling than nothing.

Passive reflectors on cats have more going for them as they do not have the heel disadvantage.

 

[Refueler]

Fog blocks radar? Really? Airborne weather radar - 3cm x band sees rain only, no way is it affected by cloud (aka fog) as the droplets are far far too small to reflect - clearly it would be useless if it did.
I very very much doubt there is any adverse effect on x band radar by fog.

Sorry but 17 years I had on the bridge with 3 and 10cmm .... fog and rain do affect the performance .... weak targets as I am saying can be lost in fog / rain ... many a time I've steered ships clear of rain and thick fog based on the large area 'shadow' return on the radar ... to avoid any possibility of target being hidden in there ..

AND get the words right ... Where did I say BLOCKS RADAR ???? that word BLOCKS implies total stoppage - go back and read correctly ... I said BLANKETS ..... meaning the weak targets can become less distinct amongst the clutter and returns ...
Go back and read where I state clearly that changing gain / clutter can reveal weak targets ...

And comparing weather radar to surface marine ?? Are you kidding ... the two are tuned / setup for completely different jobs.