[TG] [TG11] Element 9 HV digital depth loss

[Tom - Raymarine - Moderator]

Hello olygreen,

Whether you see first- or second-echo interference depends on the timing between pings - which is a function of current display range scale and Ping Rate Limit - and the current water depth, and so aren't easily predictable. For example in your 090528 screenshot you can see 1EI at depths of approx. 150, 125 and 50 feet as you step through range scales of 150, 250 and 300ft respectively. The simple rule is, if you see 1EI such as this, either change range slightly or reduce Ping Rate Limit to remove it. Always use the highest Ping Rate Limit that you can without seeing obtrusive 1EI.



There are a couple of other things that stand out in this image:

1. You appear to have a pulsed noise source which is visible as vertical stripes in the background clutter. From the regularity and timing, something like an autopilot pump might be the culprit. If you can find the source of this noise and eliminate it (what is happening on the boat in time with those pulses of noise?) you will see better sounder performance.
2. You shouldn't see anything that looks like a fish - like the clear, wide arches in the top 50-75ft in your image above - as a result of interference. If you see something like this, it's a real echo in the water. No ghost fish, regardless of whether you see 1EI or not.
3. You seem to have quite a pronounced thermocline at around 50ft. All ok, I just thought it worth mentioning since it's more clearly-defined than most instances I've seen.
   

Regards,
Tom