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

[olygreen]

Hi,
Bought my first ever Raymarine product. I am having an issue with depth loss. Lets say I am fishing in 600ft of water but I only want to see the top 100' so I change depth to manual and when I hit the + button to where the bottom is no longer on the screen the digital depth goes away. Comes back when bottom is back on the screen. Using auto depth and zoom is worthless because the picture is horrible. How can this be fixed?

link to video https://photos.app.goo.gl/666vz7V4EwezA1S88

[Tom - Raymarine - Moderator]

Hi Olygreen,

All of our sounders adjust their ping rate to the current range scale. This is because as a user you generally want the highest number of pings per second possible for greatest clarity, but the sounder needs to leave sufficient time between each ping for the sound energy to travel down and back up. In deeper water this takes longer of course, so as you go deeper the ping rate and hence scroll rate has to reduce. In order to prevent picking up echoes from previous pings (so-called first-echo interference) and avoid wasting CPU time processing sounder data that won't be displayed, the sounders don't attempt to process any echoes below the current range scale. All this means that if you're in 600' of water but range shallower than this, the system can no longer receive and process the bottom echo and give you a depth number.

There are a couple of workarounds to allow you to look near the surface and also track the bottom at the same time, each with their own advantages and disadvantages:

1. As I see that you are in the video, use Zoom to look at the near-surface band for pelagic fish and track the bottom in the un-zoomed bar with Auto Range. This is easy, but has the disadvantage that you lose resolution - as you have seen - in the near-surface view because the system sets the ping 'pulse-width' and gain to something suitable for the full range, instead of using a narrow, high-detail pulsewidth and low gain as would be normal if the range were set shallow. This will have a slower ping-rate than you would get using a manual range looking just near the surface, but I think that this is the best compromise on the Element hardware.
2. Use two different sounder channels, one set to a shallow manual range and one set to track the bottom. On our top-of-the-line CP570 sounder this would be the recommended solution, and in fact this is the key differentiator of the CP570, that it can do this still with fast scrolling. On all of our other sounders, including Element, this will result in even slower scrolling as the system will alternate pings between the two channels, with the combined ping-rate set to that of the deeper range. This is because there's one set of receive-transmit hardware within all sounders except the CP570, which is either working on one channel or the other but not both together. The only way to do this with the much simpler Element is to set up a split-screen dual-fishfinder page, and use auto-range tracking the bottom with the Sonar channel on one side and manual range looking at the top part of the water column with the DownVision channel on the other side. This isn't ideal, but it's the only other option without going up to an Axiom display.
   

In short, what you're seeing is normal behaviour for most simpler sounders when set up as you have yours set. It's specifically to allow true dual range with fast scrolling on the shallow range that we have the CP570 in our range, but that of course comes at a much higher cost.

Regards,
Tom

[olygreen]

Thank you for the response. I will keep the unit in manual range when fishing deeper than say 200ft. So if I am in 600ft of water and only looking at 100ft of water are the targets that the sonar is showing on the screen going to be accurate since the settings will be set for much shallower water then what is actually there? When trolling for salmon what is the optimal scroll rate for the screen? I believe in have it set at 50% currently. Also what about the max ping rate when fishing in deeper water but only displaying the top 100ft?

[olygreen]

Thank you for the reply. I think this is my first ever sonar that will not let me choose a custom depth range on screen while keeping the true depth. So my question is will the targets on the screen, when I am only showing the top 100ft of water in 600ft of water, be accurate or anything else to worry about? Also on the attached pictures how do i get rid of the blue mass in center of screen that follows bottom?

[Tom - Raymarine - Moderator]

In an ideal world, what exactly is it that you'd like to see, how would you like the screen image set up? The Element is designed to be a simpler system than the Axiom and higher ranges and it's not intended that it will do everything that these high-end systems will do, but I'd like to see how close we can get to that ideal.

Quote:will the targets on the screen, when I am only showing the top 100ft of water in 600ft of water, be accurate or anything else to worry about?

Yes, the auto gain setup should do a good job of showing fish targets clearly even if the bottom is not visible within that manual depth range. You may want to use a slightly lower auto gain bias (e.g. Auto -10%) if there's a little clutter on screen, since the system will be trying to use a gain level sufficient to find the bottom echo which of course it won't be able to do.

Quote:When trolling for salmon what is the optimal scroll rate for the screen? I believe in have it set at 50% currently. Also what about the max ping rate when fishing in deeper water but only displaying the top 100ft?

Scroll-rate is very much a personal preference, trading the length of history you have on-screen against the image detail. Personally I prefer a faster scroll rather than slower in order to give truer and clearer target representation.
On ping-rate though, there's generally only 1 reason that I see that you'd want to reduce ping-rate and that is to remove first-echo or second-echo interference, which brings me to:

Quote:Also on the attached pictures how do i get rid of the blue mass in center of screen that follows bottom?

If you have something that looks a bit like a thermocline, bait or plankton mass in the water column but which tracks the bottom, it may well be first-echo or second-echo interference. In your instance, when you are using a manual range that is shallower than the true water depth then first echo interference is a strong possibility. See here for more details. A strong clue that you have 1EI or 2EI is if the band in the water column shifts up or down or weakens/strengthens significantly when you change range, as in your attached images. The spiky, broken appearance of the trace is also characteristic: you are seeing first-echo interference.

A good way to remove it is to slightly reduce the ping-rate so as to break the synchronisation between the return times of successive pings. Use the highest ping-rate that you can that removes the interference. The fastest way to find the right ping-rate that will do this is to drop the ping-rate a lot (e.g. start at maybe 10 pings/second) and then increase until the interference comes back, then drop back 1-2 pings. The specific value you use will depend on the manual range scale and current depth so for best results you should change it to match changing conditions, so you need a fast method to do so.

Looking at your screenshots, I'd also like to suggest that you try one of the different colour palettes. That Classic White colour palette is popular because the white background stands out well in sunlight, but I personally am not a fan of that colour palette because any clutter there is tends to really stand out from the background (dark blue), which makes the image look more cluttered than it really is and tends to lead people to drop the gain level too much. I recommend the Sunburst colour palette instead, which still has a white background but which uses a pale yellow for weak targets (clutter) which therefore won't stand out against the background.

Tom

[olygreen]

Thank you for the reply. I have attached more pics. So assuming when I am fishing in 500ft of water but only looking at top 100ft the 2nd echo marks go away when I set ping to 8 which should give me the best picture with no 2nd echo clutter including ghost fish? Would I get false marks if I zoom out and the 2nd echo clutter was at 250ft but i zoom back in and only look at top 100ft?

2ns topic is what do i need to do to connect my 2016 merc 115 to this unit?

[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