Which Sea-Me??

boatmike

boatmike

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As I said on another thread I am considering fitting one of these transponders, but there are two. One operates only on X-Band (I think) and the other on X and S band. It's a no brainer that the dual frequency one is best but it's a lot more expensive. My knowledge of commercial and military ships use of radar is confined to re-fitting them. I have no commercial sea experience. I think I am right that in crowded waters and close quarters situations like the English Channel, Irish Sea etc. X-Band is likely to be used. S band has greater range and better discrimination in fog and rain (??) and is more likely used more in open waters away from land. Either way, am I right that most ships encountered will be either running X-band, or both? Are there many cases where S band on it's own will be running unless in say mid atlantic? If so the single X-Band one will do OK won't it?
Definitive answers from commercial users would be appreciated.
 
A very good question, and one that I would like an answer to as well (thus my bumping this back up to the top).
Are there no current or ex- professional mariners what will share their views with us?
 
bbg said:
A very good question, and one that I would like an answer to as well (thus my bumping this back up to the top).
Are there no current or ex- professional mariners what will share their views with us?
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Well... That's what I wondered too so I also asked the same question on the Ships forum. No answer there either so far. Perhaps they are all busy watching their radar screens! Seems easy to get lots of opinions on other things......

Interestingly, in the mean time I read the comparison by PBO between Echomax Active-X and Sea-Me. Seems the Echomax is better. Tried ringing Sea-Me and got no answer. Rang Echomax and got the "main man" willing to chat openly. He is shortly bringing out a dual band one too but that will also be expensive and he confirmed that his opinion is the same as mine. Most ships will have either X and S band running or just X. Personally I can't see why a ship would run on just S. Be nice to hear from some commercial guys tho,
 
Most merchant ships are equipped with both X-band and S-band radar.

S-band has a superior performance in sea clutter and in heavy rain, which are just the conditions in which a relatively small yacht will be most difficult to detect, particularly at shorter ranges.

An RTE is on my shopping list, but I will wait until a dual band model is available with power consumption and performance specs similar to the Echomax.



(ex-professional mariner, with no illusions about the bad weather visibility, or radar conspicuous characteristics, of my small plastic boat) :)
 
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"S-band has a superior performance in sea clutter and in heavy rain, which are just the conditions in which a relatively small yacht will be most difficult to detect, particularly at shorter ranges."

Yes, but does big tin turn off (or not look at) X band when S band is on?
 
Twister_Ken said:
"S-band has a superior performance in sea clutter and in heavy rain, which are just the conditions in which a relatively small yacht will be most difficult to detect, particularly at shorter ranges."

Yes, but does big tin turn off (or not look at) X band when S band is on?
Click to expand...

Can't speak for watchkeepers of the world, but basic standards require both to be monitored when in use.

Probably best not to make too many assumptions and just enhance your visibility in proportion to your concerns/depth of wallet.
 
Am I right??
X-band is used for long range radar and S-band for shorter range radar coverage.
I have Sea Me (X-band) and it has been fantastic both at detecting the presence of shipping on the open sea and giving a good return signal at a distance which allows large vessels to make course changes when appropriate.
I also have a Firdell reflector which I was told was adequate for good S-band returns.
I hope an expert Forum Guru will comment on these points.
 
Saltwater,

X band is shorter range, better discrimination, S band is long range, less discrimination - see first post.

It's worth reading this:

southern.rya.org.uk/manley.doc , which concludes that passive reflectors are useless on S band, but says Sea me on X band is effective.

The Qinetiq report assumed all ships would use X band, and tested passive reflectors only on X band. It would be really nice to know how valid this is, as the OP asks. You get the impression that testing anything passive on S band would have been a waste of time.
 
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For most simple shapes (including the trihedral "corners" that make up most so-called radar "reflectors"), the formula for radar cross section has wavelength-squared on the bottom.

In other words, the RCS of a given "reflector" is inversely proportional to the square of the wavelength. As the wavelength of S band is about 3x the wavelength of X-band, a "reflector" with a published X-band RCS of 7sqm will have an S-band RCS of about 0.7sqm.

That's why they don't advertise it.
 
deep denial said:
so what's the answer? Do they turn off x-band, or not?? Anyone out there?
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Hmmm. I don't think we have an answer to that that is at all definitive but I can't see why a ship in crowded waters would switch either off. The X-Band will either be running alone or in conjunction with S-Band I think. In open waters (mid Atlantic) perhaps but I think I will be going for an Echomax Active-X because I don't have unlimited cash and I think it will be unlikely that I meet a ship running just S-Band..... All I need to know now is that the Philippino on the bridge is watching the screen, which may be a bigger problem in practice.
 
boatmike said:
Hmmm. I don't think we have an answer to that that is at all definitive but I can't see why a ship in crowded waters would switch either off. The X-Band will either be running alone or in conjunction with S-Band I think. In open waters (mid Atlantic) perhaps but I think I will be going for an Echomax Active-X because I don't have unlimited cash and I think it will be unlikely that I meet a ship running just S-Band..... All I need to know now is that the Philippino on the bridge is watching the screen, which may be a bigger problem in practice.
Click to expand...

i may be wrong but i believe some ships radars are on a rental basis similar to zerox type machines. cost is related to hrs of use
 
Incompetence

I ordered a dual band Sea Me last November [through a well known electronic equipment retailer] They chased the order a number of times before and after Xmas and eventually got through in mid January. Sea Me then said the unit "was in the post" ...it wasn't and didn't turn up. The retailer then contacted them again ...still no response.
I gave up, cancelled my order and will wait for EchoMax come up with a dual band system.
 
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