Sea-Me See-You?

[ianwright]

Someone tell me the difference between X-band and S-bandradar please? is a RTE that only operates on X-band a good idea?
What do ships use to spot little 'ol me?
Ta.
IanW

<hr width=100% size=1>Vertue 203, Patience

 

[pvb]

X-Band and S-Band...

Many ships now have both X-Band and S-Band radars. The standard collision-avoidance radar used by most ships is X-Band (nominally around 3cm wavelength). S-Band radars have a nominal 10cm wavelength, which makes them much better at penetrating rain, fog, etc. But the target response to S-Band signals is much smaller, which is why X-Band is primarily used for collision avoidance. I believe most RTEs only work on X-Band.

<hr width=100% size=1>

 

[Guest]

Correct ....

X = 3cm
S = 10cm

Originally as I was told at college ...... and in Radar Course for Merch. - S band was preferred and developed more in the states, X-band in UK ........ how true is possibly in legend now !!!!

But I can confirm that S band is better in rain / snow / fog etc., but definition of target is crap compared to X band which also is better for navigation ......


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[Guest]

Forgot to add .....

On Big ships ----- 3cm is normally fed to the scanner via a Wave-Guide ...... looks similar to rectangular conduit, but in alloy...... 10cm normally by fat cable.

3cm can have problems with distance from Tx unit to scanner .....

Also when looking at ships scanners - you often see two sizes and the bigger looking more frame like .... that is the 10cm, the smaller enclosed smart jobbie ... normally the 3cm.

Just thought you'd like to know !!!


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[steffen]

Re: Forgot to add .....

Nigel,
What is the norm on yachts (the JRC's and Raymarine and the like), X or S.

Happy sailing, Steffen

<hr width=100% size=1>

 

[Guest]

I\'ll let you answer ....

Good thought though and it did go through my mind when posting ...... but I think it is less critical on a yacht radar because of the less power involved and shorter runs - so cable is acceptable..... a big ship radar is pushing out a lot of power and ranges of 64 nm or more are normal + the height of masts etc. to get the Tx signal / Rx signal etc......

Maybe you would like to give a comment ???? Steffen !!!


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[ianwright]

So then,,,,,,,

,,,,,,,, a Sea- Me RTE (X-band only) at £400ish is a good idea?
Would I need to use my old tetrahedral job as well in case the ship about to run me down has only the S-band set switched on?

IanW

<hr width=100% size=1>Vertue 203, Patience

 

[pvb]

Don\'t think so...

I don't think £400 is a cost-effective investment for an RTE. This is a difficult and personal choice, because it could be argued that any safety measure is a worthwhile investment. But I reckon you'd be about as safe with a Blipper.

<hr width=100% size=1>

 

[Alex_Blackwood]

Re: Forgot to add .....

Ref Fat Cable. This is in fact a round (sometimes eliptical) wave guide not a cable and on some radars is pressurised at around 5psi with dry air. Todays merchant ships normally carry two ARPA radars. One X and one S band these are normally run as two seperate units but are completely interswitchable between displays and tranceivers. ie you can have either display on either band or both displays on the same band.
It is also a regulation that ships leaving a port must have both radars fully functional in all respects. If one breaks down at sea and cannot be repaired it must be repaired in the next port of call before the vessel can sail.

<hr width=100% size=1>

 

[Guest]

Re: Forgot to add .....

Came ashore in '89 and up till then I only saw cable on 10cm jobs and waveguides on 3cm.

In fact on one ship we had an AB who took a dislike to staying on board and 'cut' the 10cm cable ....... halfway up the mast.

I don't know about 'todays' - but thats what I saw and worked with. Also it was not LAW, but recc'd that both radars worked.



<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[Guest]

Re: Don\'t think so...

The only thing I reckon that is better than a rain catching reflector is a unit that actually transmits the rec'd signal back ----- like some buoys / lightships have ... with a coded signal that displays on the CRT. But then THAT would be very expensive !!!

I like the idea of Radar watchkeepers ... but cannot justify the expense. A good reflector mounted high and in proper configuration ..... good as anything. There are fancy blippers, visiballs etc. etc. are they actually better - no proof yet I don't think.

Anyway - what ever the ideas .... a yacht disappears in waves, clutter, etc. etc. on a ships radar and is VERY hard to find....... if you can increase the echo - fine, but it really is up to the yachtie to keep a good look-out, regardless of rules and regs - as often the Merch guy cannot see you - but you have better chance of seeing him !!!!!


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[Alex_Blackwood]

Re: Forgot to add .....

QUite correct about cable, I must admit to have been talking from personal experience but yes co-ax cable is also used. I should remember to engage brain before cocking both barrels!
As far as I know it is now against regulations to sail with a defective radar. Certainaly the US Coastguard will get very, very anti if you try it. I expect that there are clauses giving exeption. but as I don't have the regs to hand I won't argue with you on that! Anyway it wouldn't be the first time I had got my facts wrong so I shall shut up on that one!

<hr width=100% size=1>

 

[Chris_Robb]

Re: So then Get a radar

Perhaps double the investment and get a radar. - I bought the Raymarine SL76 - I have absolutely no regrets now - though I was not convinced at the time - orders from SWMBO.

I keep hearing from people that yachts are nearly invisible except in perfect conditions. - I therefore prefer to see them and keep out of their way. In heavy rain they have no chance of seeing you.


Chris



<hr width=100% size=1>

 

[ianwright]

Re: So then Get a radar

Love to, but Patience is a 25ft gaffer and there is no room on the mast for the smallest of scanners. That's why I'm keen on a good radar reflection,,,,, and/or £400 worth of RTE.

IanW.

<hr width=100% size=1>Vertue 203, Patience

 

[suse]

Ian, I spotted you, or rather, Patience, in Heybridge Basin last weekend - what a pretty boat! and what a delightful setting. I came by road, though, and didnt use radar this time.

<hr width=100% size=1>

 

[Guest]

Honest - no prob ....

All things move on and to be honest I know from going on ships now as the owner of a Cargo Inspection Co. - I see some pretty fancy gear compared to what I used on the bridge !!!

Last vessel I was on .... was a Drill Ship converted to multi-purpose .......... boy - give me 5 minutes playing with that lot - I could really cock it up !!!!


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[Guest]

Correct ....

I always remember being on the bridge of a 300,000 ton tanker, transiting the channel. Moderate vis., watchmen on wings etc. Me in wheelhouse checking radar and position etc.

Tanker on my ......
This is Yacht ....... I am racing and require you to alter course ...

Blimey this guy's got a nerve !!!

Yacht racing - this is tanker xxxx - state position and intentions .....

Tanker this is yacht racing alter your course ....

I wont repeat the rest of the conversation ..... albeit I was cheered from a few other vessels at the time and CG remarked that reply was in correct sentiment but words could have been more diplomatic !! But the upshot was I could not see him till literally passing down the side about 1/2 mile off ... and there was nothing on radar .

Now lets put this in perspective ....... 1/2 mile is a lot to a yacht, but to a Merchant Ship thats FAR TOO CLOSE for anything ......... remember a ship is anything from 10 to 25 knots depending on its type etc.

It does not matter to a Marine Court about who was wrong or right - judgements are typically %age verdicts of guilt on BOTH parties ...... one party being held majority blame, but other party also partly - even though by Coll. Regs they may have right of way. Why you may ask ..... read the rules - they state clearly that if the action of the give way vessel is insufficient to prevent collision then the stand on vessel shall take such action as nevessary to reduce risk.

So as a yachtie now - I do NOT hinder ships in any way possible. I also do not like someones elses comment about Power giving way to sail in the channel - so a vessel drawing 70ft should give way to a sialing ship ????? when it is constrained by draft ..... a case already covered by the coll. regs ?????

Sorry but I have a few pet hates ..... 1) Blue Ensigns, 2) Power gives way to Sail sweeping statements, 3) Collision Reg. quotes when taken out without care for other parts of the regs ......

Back to the post and later ----- buy a Radar instead of the detector. I totally agree ..... you can get the JRC job for a little under 700 quid ...... seems a good bargain. If my mast was sufficient and didn't look daft with one on - I would be tempted ......

OK - now shoot me down !!!!


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[ianwright]

Thanks,,,,,,,,

"- what a pretty boat! "
Ta, have to admit, I agree with you,,,,,,,
Next time say hallo,I'm always ready to stop for chat, or a beer,,,,,

IanW.

<hr width=100% size=1>Vertue 203, Patience

 

[Chris_Robb]

Re: So then Get a radar

Ian - I suppose the boom sweeps the stern so that you cannot mount it there on a stick??

It really does not need to be anything above head height as you will be using it on a max of 6 miles - foreget about greater ranges,

I still think - if there is any way you can mount it - that it is the best route. In terms of current consumption, they are now very efficient, and can go on and off standby very quickly.

Chris

<hr width=100% size=1>

 

[ianwright]

Re: Correct ....

"OK - now shoot me down !!!!"
Wouldn't dream of it,,,,,,,,,
I would have radar like a shot, IF I could mount a scanner anywhere. No room on the mast, I suppose if it was really small it might fit on one or other of the spreaders. Trouble is, the laws of physics determine the size of scanners, don't they. So until some bright spark finds a way to get round that problem I'm stuffed.
Patience has a warrant to wear a blue but never does, I like the look of the red better. The blue confuses continentals anyway. As for Colregs, in open water as far as I can, I sail so that risk of collision does not arise or alter early. I try never to insist on my rights as stand on vessel except against other boats in my race,,,,,, and I only race with the OGA where the unwritten "After you Claud" operates.

So then,,,,,,,, Find me a radar whose scanner is say, eight inches in dia and weighs around five pounds and I'll be first in line.Until then I want a reflecter that works (Ha!) or an RTE that will reliably paint a nice bright blob on any radar.
I'll add it to my wish list.

IanW
.



<hr width=100% size=1>Vertue 203, Patience