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Normally I defer to your wisdom, but a few points he
Peter Bennett wrote: On 23 Jun 2005 08:02:14 -0700, wrote: .... Do they have a "warm-up" time? The three models I've used had a 90 second warm-up. They also have a "standby" mode that turns off the transmitter, but leaves the magnetron warm. Note that magnetron life (which is a finite resource) is not used up by standby time. Do you use it continously? I usually do. New users should certainly use the radar in good visibility until they are confident in identifying targets. Things don't always appear as you might expect. Likewise. A missing part of this discussion is that the novice will only be able to make marginal use of a radar. It takes some training (at least several hours, ideally more) and a lot of practice to be proficient. Even then, when its needed the most (in heavy fog for instance) the helmsman it likely preoccupied doing basic navigation, and the first watch should be ears and eyes. The only way that radar is useful is if there is a dedicated radar watch, or if the helmsman is quite experienced. How far away will it detect: 1. A ship Over 5 miles This would be a minimum. If the radar is mounted 20 feet up (this if often cited as the optimal height, though its open for discussion) the radar horizon is 5 miles. Thus, an object that has a good return at twenty feet up it theoretically visible at 10 miles, though this might be pushing the limits of a small unit. 2. A buoy with a corner reflector 1 - 2 miles, I think. Jeeze, you can see a larger buoy at 2.5 miles! Radar should see them a bit further off. Usually when I first spot a distant buoy I use the radar to tell me if that's my waypoint or just a boat. 3. A small sailboat with radar reflector about the same Again, the theoretical limit is about 10 miles, but in practice its less than half that. And remember, half the reflectors are junk. 4. A small sailboat WITHOUT radar reflector varies Under 5 miles there should be enough metal visible to give a return, but over that distance, you're only seeing a few feet of mast. How does chop affect its performance? may obscure close targets - but most sets have a "Sea Clutter" control that should help. Chop is not an big issue, however ... The beam width of small radars is +-12.5 degrees. Thus, if you're heeling 15 degrees (assuming no leveling device) you're seeing almost nothing to windward or leeward. If you're bouncing that much, your signal is intermittent. And if you're a powerboat at speed with the bow raised 15 degrees, you could be blind in front! Does bad weather affect it? Heavy rain will show up, and may obscure targets in the rain (but it takes _very_ heavy rain to do that.) Yes, but the heavy rain situation is one of the times you need the radar. |
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