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Axiom/RV-100 - Unclear image
07-06-18, 01:45 PM (This post was last modified: 07-08-18 08:21 PM by Tom - Raymarine - Moderator.)
Post: #1
Axiom/RV-100 - Unclear image
Hello,

I recently installed an Axiom 9 with the RV-100 transom mounted xducer.

I have been disappointed with the clarity of the down, side, and 3d, but realize something else must be amiss. I have searched google and these boards quite a bit, and have found meaningful information but none has applied to my scenario 100%.

This is all on an aluminum mod-V hull, 16.5' boat.
-The xducer is on a transom saver plate, so relocating it is no big deal.
-The xducer cable was run up the Sboard side gunwale with the steering and other wiring.
-The power source came from under the console, and was where the old fish finder was connected (A Garmin Striker 4, which experienced no noise or issues). This may be a common binding point.

Issues experienced thus far:
-I lose bottom after 12kts and read -.-. I realize this can be expected from these units. I was losing bottom and had a rather large rooster tail, so I remounted it higher. I now can read to a slightly higher speed, but still lose bottom--I still have a small splash/rooster tail. Is it not supposed to have any at all? Can you lose bottom if the xducer is too deep?
-Noise/bubbles (blue spheres on depth setting) or something on 3d scan. Shows a ton of them and then all of the sudden it simply goes away and reads 'normal'. This can appear or disappear randomly.
-I have seen some vertical spikes on the downscan which are shown as horizontal lines on the sidescan. I saw this when I revved the motor in neutral, but could not discern if it was electrical noise or vibrations (but do not think they're bubbles because they reach from surface to bottom).
-I have had the MFD hiccup on me with a large vertical mark on the scan and then it starts to read clean (maybe it discharged static?).
-My 3D scan at times appears that I am in a constant valley. The walls form upward, when there are no walls. If I pass over the tall wall, it goes away after it generates the surface, but this can freak you out when navigating.

I have attached some pics of the xducer mounting, and will attach screen shots of some of the issues later this afternoon.

I will be running separate dedicated power to the unit today to see if that's the culprit. I will also verify to make sure the xducer cable isn't wound around anything on its routing.

Thanks for any help in advance,
Ian
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07-08-18, 08:41 PM
Post: #2
RE: Axiom/RV-100 - Unclear image
Hello Ian,

Thanks for the transducer photos and information. I'll look forward to seeing any photos of the sounder image that you can provide, that will tell us a lot about what's going on.

As far as performance at speed goes, what matters is the signal-to-noise ratio (SNR.) A high background noise level can cause problems just as much as air across the face of the transducer, and if noise is the problem then moving the transducer up or down will generally make little improvement (though it can make things worse by adding an aeration problem.)

To understand whether the problem is low signal (air) or high noise, we recommend putting the sounder into all-manual Gain/Intensity/Surface Filter/Range (on DV, SV or chirp fishinder views, not 3D), then gradually increasing speed and seeing what changes in the image. 50% Gain, 15% Intensity and 0% Surface Filter should give good results on your sounder type. If the problem is air, you'll generally see that the clutter low down in the water column, close to the bottom, stays a fairly similar colour as you speed up but that you get increasingly wide gaps in the bottom echo. If, on the other hand, the problem is noise then the bottom echo will stay continuous as you speed up but the clutter in the water column above the bottom will get stronger and darker with increasing speed, until it's nearly the same colour as the bottom profile. It is possible to get both problems at once.

Regards,
Tom

Raymarine since 1999.
Interests: Diagnosis of problems in sonar/fishfinders, NMEA2000, ethernet comms, autopilots
Location: Sydney, Australia
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07-09-18, 08:35 PM
Post: #3
RE: Axiom/RV-100 - Unclear image
That helps, thanks for those details Tom.

After reading your post, I am thinking I have experienced both issues.

I took it out again, prior to your reply, with a few changes for more testing. Sorry but none of the attachments are with the manual settings as specified. I will re-take some images next time out.

-I adjusted the xducer up 5/16". The rooster tail/spray was greatly reduced. I then had my wife captain the vessel so I could carefully peer over the transom. The rear 3/4 (farthest from transom) of the xducer was skiing on laminar water perfectly at 15-20kts--no bottom, but the radius on the front nose was still slightly splashing/plowing some water. I will be moving it up slightly once more to avoid contacting the top half of the forward face of the radius--if that makes sense haha. I am thinking this turbulence on the front end and/or hull generate bubbles for the xducer.(I assume this is due to bubbles. Attachment: bubblewashout)

-I re-ran my power supply wiring straight from the battery and re-routed the xducer cable to avoid all other cables the best it can. I only connected the ground(s)/Neg cable on the new run (no binding on vessel), and didn't connect the + direct to battery because it's currently switched on the console main power. I'm used to noise being introduced through the negative/ground in systems...do you find both sides of supply affect clarity?

-I saw an improvement on clutter/noise, but still had the monitor pause momentarily twice, display a vertical blip, and resuming scanning. This is of most concern.(Attachments: StutterBlip and StutterBlip2)

-I noticed my propwash shows really far out in space on the 3d. Like 20-50ft down when I accelerate. Is this common on the spatial relation near the boat on 3D? Are the 3 vertical lines (3 Rev/acceleration pumps) common on the downscan and 2d due to bubbles, vibrations, or is that electrical? (Attachments: Propwash, propwash2)

-I noticed my motor blocks the sidescan. I don't know if I caused it with an angle to transom adjustment (likely), but I can get it out of the way by trimming up some. Kind of a pain. I will have to tweak the angle more and see (Attachment: Putmotordown)

-The perspective of the shoreline on 3D seems far down from the boat. The xducer is parallel to the concrete when on a trailer. Is this something messed up in the angle, settings? I was about 40' off the shoreline on the first picture, and about 20' out on shoreline 2. Kind of falls in line with the propwash depiction though. (Attachment: Shoreline, Shoreline 2)

-Is downscan supposed to be more clear than this? Seems like so from what I've seen on the internet, but this is the best it gets for me (Attachment: DownscanSharpness)

-Does the sidescan typically look like this? (Attachment: SideScanStreaks)

Sorry for the million questions, and thanks for any help you may be able to provide. I will send you screen images with the requested settings once acquired.

Best Regards,
Ian
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07-16-18, 02:57 AM (This post was last modified: 07-16-18 03:00 AM by Tom - Raymarine - Moderator.)
Post: #4
RE: Axiom/RV-100 - Unclear image
Hey Ian,

Quote:still had the monitor pause momentarily twice, display a vertical blip, and resuming scanning. This is of most concern.(Attachments: StutterBlip and StutterBlip2)

How long did it pause for? That's not something I've come across myself. Normally I'd say restricted supply or changing ping-rate because of bottom-lock-loss, but neither of those look like the case in your screenshots.

Quote: -I noticed my propwash shows really far out in space on the 3d. Like 20-50ft down when I accelerate. Is this common on the spatial relation near the boat on 3D? Are the 3 vertical lines (3 Rev/acceleration pumps) common on the downscan and 2d due to bubbles, vibrations, or is that electrical? (Attachments: Propwash, propwash2)

The three vertical streaks in the fishfinder and DV views do look like a sudden increase in background noise level, but there's no way to tell from an image alone whether it's acoustic or electical noise. I think that the increase in noise level is what's giving the appearance of a lot of clutter in the water column on the RV view, but given the range, I'm confident it's not really your own wash. The reason why it's showing to port only is, I expect, that the real signal levels are lower from that side because of the motor.
It'll be good to see what you get on the all-Manual setup when you increase speed like this.

Quote:-I noticed my motor blocks the sidescan. I don't know if I caused it with an angle to transom adjustment (likely), but I can get it out of the way by trimming up some. Kind of a pain. I will have to tweak the angle more and see (Attachment: Putmotordown)
It's unfortunately hard to avoid this kind of thing with a transom transducer. It's a bit of a compromise between the convenience and cost-saving of the single transducer against the improvement in the image that results from the through-hull split pair, with tilted elements. I always recommend through-hull faired transducers whereever they're feasible, they are just the best for optimum sounder image. Moving the transducer closer to the outboard may (slightly counter-intuitively) help in your system, at the expense of a bit more noise and increased risk of aeration. Make sure it's not putting aerated, turbulent water across the engine intakes though: starving the engine of a clean flow of coolant water isn't cool.

Quote:-The perspective of the shoreline on 3D seems far down from the boat. The xducer is parallel to the concrete when on a trailer. Is this something messed up in the angle, settings? I was about 40' off the shoreline on the first picture, and about 20' out on shoreline 2. Kind of falls in line with the propwash depiction though. (Attachment: Shoreline, Shoreline 2)

Because of the shape of the RV beams, the surface clutter and the way the signal processing is done, the bottom image won't come all the way to the 0ft depth line on the screen. Your images look normal for a shoreline (the 'deep' area further out from the shoreline on that side is the sounder's interpretation of having no signals bouncing back from greater range on that side - it thinks there's probably a big drop-off and everything behind that is in 'shadow'.)

Quote:-Is downscan supposed to be more clear than this? Seems like so from what I've seen on the internet, but this is the best it gets for me (Attachment: DownscanSharpness)

The Intensity is a little higher than I generally prefer to use, personally, which is saturating some of the bottom echoes and losing some detail there. Other than that, I suspect that you'll see an increase in clarity if you reduce the scroll-rate, and also view in a larger window (a lot of the graininess in your image is just the limited resolution of the LCD in a small window, some of the fish targets in the water column are only 2 or 3 pixels across, for example.) How does it look full-screen?

Quote:-Does the sidescan typically look like this? (Attachment: SideScanStreaks)

The appearance will change a lot depending on your boat-speed and scroll-rate, amongst other things. The streaks that you're seeing are a function of your very low speed and what I would guess is a fairly high scroll-rate: things are staying in the SV beam for quote a long time and being stretched out in the image. The bright streaks are almost certainly fish targets (nice ones, given the brightness, size and range: go after them!), whilst the 3 or 4 brighter patches with dark shadows behind that show up down in the bottom right (above-right of the Range +) are likely to be mid-water fish or schools that are casting a shadow on the bottom. You can get an idea of their size and height off the bottom from the density and size of the shadow and separation between the shadow and target. All good stuff to be looking out for. We have a championship-winning marlin skipper here in Australia who uses marks very like those when chasing small black-marlin inshore in 30-80m of water. He swears by it: spot a mark like the one half-way up your image, ~70ft out, circle round, hook up.

Does this answer some of your questions?
Regards,
Tom

Raymarine since 1999.
Interests: Diagnosis of problems in sonar/fishfinders, NMEA2000, ethernet comms, autopilots
Location: Sydney, Australia
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07-16-18, 08:35 PM
Post: #5
RE: Axiom/RV-100 - Unclear image
Hello Tom,

Thanks for the thorough response--it is much appreciated.

Quote:How long did it pause for? That's not something I've come across myself. Normally I'd say restricted supply or changing ping-rate because of bottom-lock-loss, but neither of those look like the case in your screenshots.

It is about a 2-3 second hiccup.
It has happened more than once, with different grounds/negative connections (one grounded at console and one a dedicated run from battery). The +12V remains the same on both trials, but going by the restricted comment I may just change it to the dedicated cable run for testing. I can always add a switch later.

Quote:The three vertical streaks in the fishfinder and DV views do look like a sudden increase in background noise level, but there's no way to tell from an image alone whether it's acoustic or electical noise. I think that the increase in noise level is what's giving the appearance of a lot of clutter in the water column on the RV view, but given the range, I'm confident it's not really your own wash. The reason why it's showing to port only is, I expect, that the real signal levels are lower from that side because of the motor.
It'll be good to see what you get on the all-Manual setup when you increase speed like this.
This makes sense. Thanks for the rationalization.
I am eager to hit the water with the fixed settings. I will try to make it happen ASAP, but it may be next week at earliest.


Quote:It's unfortunately hard to avoid this kind of thing with a transom transducer. It's a bit of a compromise between the convenience and cost-saving of the single transducer against the improvement in the image that results from the through-hull split pair, with tilted elements. I always recommend through-hull faired transducers whereever they're feasible, they are just the best for optimum sounder image. Moving the transducer closer to the outboard may (slightly counter-intuitively) help in your system, at the expense of a bit more noise and increased risk of aeration. Make sure it's not putting aerated, turbulent water across the engine intakes though: starving the engine of a clean flow of coolant water isn't cool.
10-4. I would have gone closer to boat center, but I would have had to place the transom saver over a water inlet (first set of pics) to avoid being downstream of an interruption. I can counterbore the plate to clear the cover while still allowing flow if xducer relocation becomes a necessity.

Quote:Because of the shape of the RV beams, the surface clutter and the way the signal processing is done, the bottom image won't come all the way to the 0ft depth line on the screen. Your images look normal for a shoreline (the 'deep' area further out from the shoreline on that side is the sounder's interpretation of having no signals bouncing back from greater range on that side - it thinks there's probably a big drop-off and everything behind that is in 'shadow'.)
Oooh, I got ya. I can definitely make more sense of when I experience this condition and understand the 'why' after the 'drop off'/'shadow' comment. Thanks. Do you think software could net out the depth on the graphical representation for a better visual depiction of the bottom? Or is there a downside to this?

Quote:The Intensity is a little higher than I generally prefer to use, personally, which is saturating some of the bottom echoes and losing some detail there. Other than that, I suspect that you'll see an increase in clarity if you reduce the scroll-rate, and also view in a larger window (a lot of the graininess in your image is just the limited resolution of the LCD in a small window, some of the fish targets in the water column are only 2 or 3 pixels across, for example.) How does it look full-screen?
I am excited to hear this and looking forward to tinkering with the scroll rate. I have not touched the it at all. I figured it was some auto setting as well (newb haha). Awesome.

I will get some full size images on next outing.

Quote:The appearance will change a lot depending on your boat-speed and scroll-rate, amongst other things. The streaks that you're seeing are a function of your very low speed and what I would guess is a fairly high scroll-rate: things are staying in the SV beam for quote a long time and being stretched out in the image. The bright streaks are almost certainly fish targets (nice ones, given the brightness, size and range: go after them!), whilst the 3 or 4 brighter patches with dark shadows behind that show up down in the bottom right (above-right of the Range +) are likely to be mid-water fish or schools that are casting a shadow on the bottom. You can get an idea of their size and height off the bottom from the density and size of the shadow and separation between the shadow and target. All good stuff to be looking out for. We have a championship-winning marlin skipper here in Australia who uses marks very like those when chasing small black-marlin inshore in 30-80m of water. He swears by it: spot a mark like the one half-way up your image, ~70ft out, circle round, hook up.
Wow I missed out! haha I have gone over the images, thanks for the details!

Quote:Does this answer some of your questions?
Regards,
Tom
Thanks for your time Tom, you've been a great help thus far! I will update you with fixed setting images on my next outing so we can further understand.
-Ian
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07-17-18, 12:35 AM
Post: #6
RE: Axiom/RV-100 - Unclear image
Ok, I'll look out for your images.

Tom

Raymarine since 1999.
Interests: Diagnosis of problems in sonar/fishfinders, NMEA2000, ethernet comms, autopilots
Location: Sydney, Australia
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