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50 Cal
14th Mar 2003, 01:27
Good day all,

Just a few questions to the WX Radar guru's out there....The B737NG wx radar seems to be ultra sensitive to any or even the very slightest bit of precip. Even adjusting the gain from max down to min on even the smallest of showers seems to make no effect on the picture...I have never encounterd this before as wx radars I have used before [ in both bands], adjusting the gain say two divisions [ maybe 6 or so decibels] had a marked effect on the presentation.

The routes that I fly are not high in moisture content nor can I recall the model number...I think it's a standard fit for the NG.

Any thoughts as to desensitize it apart from adjusting the tilt????

Thanks

dvt
15th Mar 2003, 01:46
Seems like you might have the old control head. On this head, you can't reduce the gain from the CAL setting. YOu can only increase it.

The radar is very effective at high/mid altitudes. However, in the traffic pattern it becomes prone to a phenomena known as "REDOUT". Simple rain showers show up as RED, to the point of totally filling the screen with RED.

The only things you can do are...
1. Get a good weather briefing on the liklihood of convective activity in the area.
2. Analyze the weather from above before you descend into the terminal area. If you're descending through FL250 with +3 degrees of tilt, and you're painting cells as RED, plot these on your map using the FIX page. Obviously, any cells painting RED over FL250 can be very hazardous. Use the tilt to plot storms that are painting shadows. The only way to see shacows, is to point the RADAR at the ground. Don't forget about the PAC Alert Bar on these Radars. They're very handy, but you have to be 80NM or less to get them.
3. Work AROUND. The only way to lower the gain in these older control heads is via the MAP mode. Desceding into the terminial area you can select MAP. This biases the gain downwards by about 10dbz. Which amounts to one color change. This is very helpful, to know this in a Redout situation.

DVT

50 Cal
16th Mar 2003, 23:30
Thanks dvt, I'll try those suggestions and see how it goes.

Thanks for replying.

50 Cal

Diesel3
17th Mar 2003, 12:31
The manual issued to me for our NGs states:

Gain control - Sets receiver sensitivity to enhance ground mapping in MAP mode only. System automatically sets gain in other modes.