Radar for sailboats

On Mon, 7 Jan 2008 20:58:40 -0000, "Robert Miles"
<rmiles DeleteThis @zetnet.co.uk> wrote:

>Hi,
>Looking at fitting Radar to my Beneteau 361.
>I had a JRC 1000 a few years ago.. I liked the low power drain and small
>radome.
>JRC don't market in the UK anymore so options seem to be Furuno or Furuno?
>
>Furuno make an 18" 2Kw radome. not sure how big the cable to the display is
>though, the JRC was pretty large! About an inch diameter! I was looking for
>something simple to install

I've told you millions of times not to exaggerate!

I'm sure the cable on my JRC1500 radar was only about 1/2 inch
diameter.
>
>Garmin seem to make radars these days.. but 4Kw? I will be running the
>engine to keep the radar going.. might as well get a motor boat!

Remember that the advertised power of a radar is the peak transmit
power, and the radar will transmit for less than 0.1% of the time. I
might expect a 4 KW radar to use about 1.5 times as much power as a
2KW, as most of the power will be used heating the magnetron, rotating
the antenna, and operating the display, with only a small portion
going towards the RF output power.
>
>Any thoughts on who makes small low power radomes for sailors please?

Furuno, Raymarine, Garmin. I've also seen Koden mentioned recently.

>
>Regards
>
>Bob Miles
>

--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca
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In article <47829279$0$761$4c56ba96@master.news.zetnet.net>,
"Robert Miles" <rmiles RemoveThis @zetnet.co.uk> wrote:

> Any thoughts on who makes small low power radomes for sailors please?

First see what you need:
If you want it for tight waters a radome might not have sufficient
resolution, as this is dependent on the lenght of the antenna.

see this post <marc.heusser-CEEB75.17012302012008 RemoveThis @news.uzh.ch> (lenghty
discussion of all the aspects under the title Koden radars:

radio beam width [degrees] = 2.1 / Antenna Length [m]
ie a 40 cm radome gives 5.6°
a 65 cm cm (2') radome gives 3.2°
a 90 cm (3') open array gives 2.3°
a 120 cm (4') open array gives 1.8°
a 180 cm (6')open array gives 1.2°

Then: eg 4kW is the peak power.

As for manufacturers apart from Furuno there is now Koden it seems, and
have a look at Simrad DX-60 if you want a radome.

HTH

Marc

--
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> First see what you need:
> If you want it for tight waters a radome might not have sufficient
> resolution, as this is dependent on the lenght of the antenna.
>
> see this post <marc.heusser-CEEB75.17012302012008 RemoveThis @news.uzh.ch> (lenghty
> discussion of all the aspects under the title Koden radars:
>
> radio beam width [degrees] = 2.1 / Antenna Length [m]
> ie a 40 cm radome gives 5.6°
> a 65 cm cm (2') radome gives 3.2°
> a 90 cm (3') open array gives 2.3°
> a 120 cm (4') open array gives 1.8°
> a 180 cm (6')open array gives 1.2°
>
> Then: eg 4kW is the peak power.
>
> As for manufacturers apart from Furuno there is now Koden it seems, and
> have a look at Simrad DX-60 if you want a radome.
>

Thanks for the posts.. to expand a little, and bemoan the fact that I can't
get what I want! ( do small sail boat users feature in the designers mind at
all?)

Most times I use radar for collision avoidance and sometimes to identify
Racons.
The most important factors I look for are low power consumption, and a small
radome to minimise impact on the sail ( Friction when tacking) and CoG.
As some folk have said, the pulse power can be higher but average power kept
low. I guess that there is a trade off with a lower pulse repetition
frequency to reduce average power.. or is the rotational frequency reduced
to compensate.. ?
The sales blurb has a lot of attention on beam width and sexy graphics and
colours for the display but less on usability and installability in small
yachts?

I guess I can get an 18" radome and 2Kw from a number of suppliers..but I
quite liked the 1.5Kw 12" Radome of the JRC 1000 - 30W average power
consumption .. 25% - 40% saving on power!

Did the job for me! Size isn't everything..

Just have to compromise.. again..

Regards

Bob
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"Robert Miles" <rmiles.DeleteThis@zetnet.co.uk> wrote in message
news:4784011d$0$771$4c56ba96@master.news.zetnet.net...
> As some folk have said, the pulse power can be higher but average power
> kept low. I guess that there is a trade off with a lower pulse repetition
> frequency to reduce average power.. or is the rotational frequency reduced
> to compensate.. ?

The pulse rep rate and rotation speed are probably going to be about the
same in the 2KW and 4KW radome units. The power consumption doesn't scale
with the pulse power because most of the power is used in the drive motor,
processing electronics, magnetron filament, etc -- stuff which draws about
the same amount regardless of the transmit power, or at least not 2x the
power. The transmit pulses are of such low duty-cycle that they don't
contribute that much to the total power consumption.

If there is a major difference in power drain, it is probably due to other
design features.

- Paul
- S/V VALIS
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