Southampton Boat Show - VIP ticket - Sunseeker/Princess - radar

[jfm]

You are still very mixed up on your logic becuase you continue to think that horizontal beam width matters. It doesn't.

The vertical beam width (from the Raymarine website) is 25 degrees. (On a 40foot flybridge, incidentally, you could subtend most of that if standing up and if the scanner were at your waist height).

The horizontal beam width for the purposes of these calculations is irrelevant. It doesn't matter whether it's greater or less than the vertical beam width, becuase it's a complete red herring. If you dont "get" that point, you are not understanding this at all.

In fact, you might as well think of the horizontal beam as 360degrees, and think of the radar beam as a disc that thickens up at a 25% angle. The only thing that matters to the question of how much microwave your body is exposed to is the angle subtended by your body to the radar, and that value is completely unaffected by the beam width, which is why the beam width is irrelevant.

 

[Cymraeg]

Took a guided tour of one of the RNLI's lifeboats a couple of weeks ago .... to the side of the steps to the flybridge (except they don't call it that) is a big notice about not standing near the transmitter when the unit is powered up but not rotating, but OK when the scanner is going round. As there weren't any seats upstairs on the boat all the crew had to stand, which put the scanner only a foot or so higher than their heads. As I would assume it was a pretty powerful set and the RNLI know what they're doing, I would agree that physical injury is much more likely than radiation. /forums/images/graemlins/ooo.gif

 

[jfm]

Hmm, interesting. I'd guess from that that they have the radar powered up and transmitting on standby even when not rotating. According to Raymarine website, on standby they don't do that. It seems they have the magnatron heater on but the thing isn't actually transmitting. As far as i can tell from the website...

 

[Kieran_Breheny]

If you ask Raymarine for their safety calculations for their Radar they can send you a 'white paper' outline document explaining the calculation and overall recommendation. 'although the power absorption by a user x distance from x radar is 1/1000th that of a mobile phone and well below recommended amounts....even small amounts of microwave radiation should be avoided if possible and the radar should not be sighted at eye level...' or something very close to this. Just ask them for a copy.

 

[Hurricane]

It was said - not sure if it true or not - that the big radar that used to be in the middle at Heathrow was timed to switch off at the instant that the rotation passed in line with the air traffic control center.
Might have been a rumour though to keep them from moaning.

 

[MapisM]

[ QUOTE ]
According to Raymarine website, on standby they don't do that. It seems they have the magnatron heater on but the thing isn't actually transmitting. As far as i can tell from the website...

[/ QUOTE ]I never bothered to check that on the manual, but I can tell you for sure that also in my Furuno the current absorbtion is much lower (almost irrelevant) in stby, compared to normal operation.
Besides, common sense would suggest that if the thingie should transmit also on stby, they could as well make it spinning and get rid of the stby function completely....?

 

[MapisM]

[ QUOTE ]
If you ask Raymarine...

[/ QUOTE ]Now that's very interesting.
Knowing a fair bit of how companies deal (or should I say try to deal?) with these issues, I would translating it more or less as follows:
We are in the foggiest with regard of any potential damage which our products might create to anyone. Therefore, do with it whatever you want as long as you're not asking us a refund.

 

[Wiggo]

[goes away to think hard about this...]

 

[Wiggo]

OK, I accept that the horizontal beam width is irrelevant (as is its shape). Mr Normal's trunk probably subtends about 11* at 3m from the scanner, so gets around 3% of the available energy, while his head gets significantly less. The 25* vertical beam would indeed probably completely cover him when standing, so I will make a note to only crawl around on the f/bridge.

If I can muster the enthusiasm, I'll work out the total energy dose later.

Now, from my (much) earlier career in electronics, I do recall stories of military radar sets we worked on being able to knock down birds in flight, but these were pretty esoteric pieces of kit. On balance, I'm comfortable enough with my radar to leave it on most of the time. Besides, if you don't practice 'reading' targets in good visibility, it'll be sod all use to you in a pea souper.

 

[jfm]

Ref doing the energy calcs, i have never done them becuase i dont think i could interpret the result. I mean, if you compute that Mr Normal has been squirted with 10 joules of microwave energy in an hour on the flybridge, or whatever, where do you go from there? I dont think there's any settled medical view on whether X joules is a bad or a good thing.

So just working on gut feeling and the baked beans analysis you mentioend earlier, I'd agree with you that the power levels here seem so tiny that there's probably no material harm, and if a boat builder happens to offer you a boat that "floats your boat" and sticks the radar high (as happened to me) well you might as well take it /forums/images/graemlins/grin.gif