[TG] RV-220/Axiom Issues

[JHH83]

I recently installed a pair of RV-220 transducers and interfaced them with an Axiom 9 running the most current Lighthouse software and have immediately run into several issues. The transducers are installed on my Contender 25 Open (24.5* deadrise) as close to the keel as possible, and are not in line with any strakes or other parts of the hull that should cause turbulent water.

1. When on a plane in even slightly choppy waters, the MFD has several times displayed a message to the effect of "No transducer connected" and stated that it needed to be restarted. Upon restarting the Axiom, everything worked again.

2. While running out to fish, I lost all depth around 500-600 feet. I ended up heading out to about 900-1000 feet and fished for a while, never regaining depth at any time until returning to about 120 feet. At trolling speeds, the depth read "-.-" and the MFD showed repeated garbled vertical lines in both sonar and downvision (see attached photos). After returning to shallow waters, all fishfinding and depth functions then returned on their own.

3. Even when in shallow waters where everything seemed to be working, in 3D mode, the 3D always seems to show a steep wall on each side of my boat, when I'm clearly over a flat, shallow bottom.

[Tom - Raymarine - Moderator]

Hello JHH83,

Sorry for the long delay in replying, your post seems to have been missed somehow.

Quote:1. When on a plane in even slightly choppy waters, the MFD has several times displayed a message to the effect of "No transducer connected" and stated that it needed to be restarted. Upon restarting the Axiom, everything worked again.

That's interesting. I have come across one similar case where the transducer detection stopped working at higher speeds, and in that case the cause appears to have been unstable charging voltage from the outboard (outboard charging voltages can be anything other than straight DC, despite what averaged voltage a multimeter may show.) I am awaiting an oscilloscope image of the power supply from that boat from the dealer, but the problem's been resolved in the meantime by installing a separate House battery, isolated from engine charging. It would be great to try to identify whether engine RPM (charging supply) or vibration is the cause in your case, and I would love to see an oscilloscope image of the charging supply (taken by a good technical service dealer) to see whether that's a factor.

Quote:2. While running out to fish, I lost all depth around 500-600 feet. I ended up heading out to about 900-1000 feet and fished for a while, never regaining depth at any time until returning to about 120 feet. At trolling speeds, the depth read "-.-" and the MFD showed repeated garbled vertical lines in both sonar and downvision (see attached photos). After returning to shallow waters, all fishfinding and depth functions then returned on their own.

500-600' is on the upper limit of the depth capability for the low-power RV transducers, so I think that you're losing the bottom on the way out just because of normal low signal level in that depth. Once the bottom lock is lost, it's much harder for a sounder to reacquire a depth reading on the way back in because it doesn't know where to look. Using an appropriate manual Range and setting Gain to Auto+50% will both help the system to do as quickly as possible. Using the chirp Sonar instead of DV mode will help, as the sonar has better depth penetration because of its lower frequency.
The images you've posted are perfectly normal in Bottom Search mode, where the system's cycling through different range/gain/pulse-width/ping-rate combinations in order to scan the full depth range for the bottom.

Quote:3. Even when in shallow waters where everything seemed to be working, in 3D mode, the 3D always seems to show a steep wall on each side of my boat, when I'm clearly over a flat, shallow bottom.

At the outer fringes of the RV 3D image, where the signal levels are weakest compared to the background noise (there is always background noise/clutter in any sounder system), the algorithm that interprets what sounder echo points represent part of the bottom and what are in the water column does tend to draw the bottom as inflecting upward like that. That's quite normal. The effect is more pronounced at either very long or very short range-scales, or probably at unusually high or low Gain levels. If you use a moderate range and gain the effect should be pretty minimal.

Regards,
Tom