Werkt de Sea-me echt ?

Zoals ik er nu tegen aan kijk luidt dat antwoord: misschien een beetje. En misschien werkt hij wel beter als je hem op de masttop monteert. Van de claim van de fabrikant: "Its the best way to drastically improve radar visibility" heb ik niets gemerkt. Onderstaand de e-mail correspondentie hierover (in chronologische volgorde) met Munro engineering, de fabrikant.

From: Douwe Fokkema

To: 'Munro Engineering'

Sent: Thursday, September 14, 2006 5:11 PM

Subject: practical experience with the Sea-me

Dear Peter,

 Following below some practical experience with the Sea-me as mounted on my Hallberg Rassy 31 Monsun. The Sea-me is mounted on the spreaders 7 meters above sea level, no room in the top. The experience is from a trip I just made from Holland to the Canaries.

-          in calm weather a friend of mine saw no difference on his JRC1000 when I switched the Sea-me on and off.

-          a big tanker reported that he could not distinguish me against the seas on his radar until 1.5 mile away, rough sea, waves 3 meter

-          another big ship that I contacted regarding my visibility on the radar reported that I was just visible on the radar on a distance of 4 miles, when I switched the Sea-me on the echo was “a little bit better”. Moderate sea, waves 1.5 meter.

This leaves me with the impression that the Sea-me does work, but does not give me the visibility that I expected from it. The unit seems to work ok as the red light goes on when there is a ship on 30 miles distance. Besides the Sea-me I have kept the original radar reflector (this transparent tube thing), mounted below the other spreader. In the above cases the Sea-me was not shielded by the mast.

Please comment on these experiences, should I expect better performance?

Kind regards,

Douwe Fokkema

Dear Peter,

 Van: Munro Engineering
Verzonden: maandag 18 september 2006 12:20
Douwe Fokkema
Onderwerp: Re: practical experience with the Sea-me

Dear Douwe,

Thanks for your email.  I would certainly expect a better performance than that which you describe.  Reports we receive from other users, repeat buys by government agencies and our own trials all confirm a much better performance.
We specifically say in the User Handbook that the antenna should not be mounted on an a spreader.  In addition to mast shielding and vulnerability there is also the possibility that the mast, because it will be very close to the antenna, can act as a reflector and cause feedback within the antenna electronics.  We also recommend that a Glomex V9173 mount be used to overcome any crowding at the masthead.  The attached photo shows how it does this.
When radar reflector manufacturers are testing reflectors they do it on the basis of consistency of return rather than the subjective "it's a little better" approach which you describe.  To do this we count the number of returns to scans we get at different ranges.  This is then an objective measure of performance.  The other reason for doing it this way is that considtency of return is vital in these days of ARPA which requires a minimum 50% return rate.

Best regards

Peter Munro
Munro Engineering Limited
Stoke Trister
Somerset BA9 9PL
Tel/Fax: 0044 1963 34184

Dear Peter,

Thanks for your reaction.

-          Indeed the user manual states that the unit should not be mounted on the spreader because: “as the mast will then partially obscure the antenna”. I have accepted the fact that the mast will obscure the antenna, considering this will happen on say 10 degrees out of 360 I consider this acceptable. The manual does not say that the unit may not work at all due to interference.

-          In the three cases that I quote the results vary from: “It’s a little better”, “no difference”, to “I can not distinguish you”. This is what counts for me , can I be seen by another ship. Until now I have not seen the results that justify your statement on your website: Its the best way to drastically improve radar visibility

-          At a next possible occasion I will move the unit to the masthead, as I will have to take the mast down for this job this may take some time, may be even after my circumnavigation when it is no longer needed. I also have my doubts if this will drastically improve the radar visibility and is worth the effort.

With kind regards,
Douwe Fokkema