Michael MB

Sorry about the delay to responed....I have been moving house and in Hospital. To answer in a technical frame, a false echo or return is a spurious noise source. Ok now in english. I will deal with is in two ways first sonar then radar. In water we have eddie currents, flow noise and biological's. These all cause different types of noise. Eddie currents generate echos the may or maynot have doppler associated with them Doppler is important in ASW because it is how we classify Non Sub contacts i.e. A reef or wreck wont have doppler as it isnt moving, however this is where eddie currents reak havoc. They move within a current and will have significant doppler FROM MEMOERY 1knot of movement is equal to 12hz of doppler. So if your current is moving at say 3 knots that will give you 36hz of noise that your sonar trackers will interperate as movement, therefore POS SUB. In Australia we have signifcant eddie current that last from a few minutes to a few days. Flow noise is generated when water moves over a solid object. This will cause doppler on a non sub target but will be picked up by a good operator as the target will not move. Also boundries between temperture layers call Thermoclines and density differences will also cause some noise. Biologicals, my favorite! The first thing everyone thinks of is whales but the are other things in the sea. Schools of fish produce echoes with doppler. However the doppler is not constant....... I havnt finished I having a break more to follow

For all Harpoon games I would love to see false echo's. This affects sonar more than radar, and I have seen SAU's prosecute non sub targets more than once.

We have been able to bounce SSN's for years now. The things are as noisey as hell. Ever time we did a CASEX with a SSN we found it.