Radar radome - vertical beamwidt?

[olavs]

Raymarine specifies horiontal beamwidth for their radar radomes but doesn't mention vertical beamwidth.
I believe the latter is of importance in order to be able to calculate the deadzone around the boat as a function of antenna mounting heighth.
Am I missing something here?
My antenna will be mounted 6-7 meters above sea /forums/images/graemlins/confused.giflevel and I would like to know the radius of the deadzone.
Thanks.

 

[ShipsWoofy]

If I recall it is about 22°. It should be in the specs in your manual, if you have no manual most of them are downloadable on the Raymarine site.

 

[pvb]

According to the catalogue...

According to the catalogue, all Raymarine scanners have a vertical beam width of 25 degrees.

 

[alan]

It is stated somewhere on the Raymarine specs on their web site. I was reading it only last week, and as stated it is around 20 degrees.

 

[pvb]

Yes, it\'s on the website too...

On the specs page - 25 degrees.

 

[malcp]

Re: Yes, it\'s on the website too...

Don't forget this is 12.5 Degrees above and 12.5 Degrees below the scanner's horizon.
The scanner will emit power at greater angles than this but at less than half the main beam power. This should mean you'll still get signal returns for the short distances around the boat, but the main problem will be sea clutter. For greater scanner heights you will have to increase the sea clutter, which reduces sensitivity for close in targets. This may increase your apparent dead zone. I suspect this will be somewhat difficult to calculate, as it will also depend on the seastate.

 

[coco]

Re: Yes, it\'s on the website too...

Never had a radar, so this is probably a stupid question. Does the angle of +- 12.5 deg. mean that on a sailing boat heeling at 20 deg. you will never be able to see targets located on some portion of the "upwind side"?

 

[malcp]

Re: Yes, it\'s on the website too...

Not a stupid question at all. A large angle of heel will affect the target detection range on each beam. As the effective transmitter power at the beamwidth points (ie +/-12.5 Deg) is half that at the boresight (by definition), I would expect the effective range to reduce to 70% of that unheeled. Beyond this you would need to see the polar plot of the scanner to calculate further range losses. To overcome this gimballed radar mounts are available. But, in bad viz perhaps you'd be motoring not sailing?