Interference with Chirp transducers

[ObsidianPhish]

I have had a series of sonars and transducers on my BW 285 Conquest. Initially I had the thru hull and a CP300, to which I added an a98 with the CPT 100 for down vision. I operated these 2 together with no issues. I then replaced the CP300 with the CP470 and added a TM275LHW 1k Chirp transducer which was mounted approx 12" from the CPT 100. I was aware there there might be interference /cross talk. As long as I ran the DV which I believe scans at 230 kHz, the High chirp (150-250 kHz) worked well. I disconnected the thru hull standard 50/200 transducer.

My issue is that now I have replace the CPT 100 with the Axiom 3D Transducer the following occurs:

I lose bottom at depths of 30 to 300 ft @ less than 10 knots. ( I lose it deeper and faster but I can manage that by switching to 50 kHz). I lose bottom on the CP470/TM275 first and regularly. I also less frequently, lose bottom on the Axiom. I should note that because Lighthouse II and 3 software are currently incompatible I don't have the Axiom on the network, only NEMA 2000, so they basically run independently.

If I reboot the 470 I gain bottom back sometimes for 5 mins sometimes for 45 mins.
If I change the 470 to 50 kHz I regain bottom but then if I move to High Chirp the above situation reoccurs.

I am also getting significant interference on the Axiom in High Chirp mode, so many artifacts that it makes it unusable regardless of whether the 470 is pinging or not.

I am running the latest firmware and latest versions of both Lighthouse software releases.

I have spoken to technical support in the US (not Columbia) and been given different opinions on whether this is being caused by Chirp interference (from highly unlikely to most definitely. Can you provide any suggestions or recommendations to help resolve this?

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum ObsidianPhish,

Please click here to view a FAQ addressing the subject of Transducer Frequency for CHIRP/DownVision, SideVision, and RealVision 3Dâ„¢ transducers. As indicated within the referenced FAQ, the CHIRP/DownVision (used by Dragonfly, ax8, eSx8, and CP100 products), SideVision, and RealVision 3Dâ„¢ transducers are all designed to chirp across a 60kHz range centered on 200kHz when using CHIRP conical sonar. Replacement of the CHIRP/DownVision with a RealVision 3Dâ„¢ transducer would thus expose the system to the same frequency range which had been previously chirped by the CHIRP/DownVision. As the problem first manifests itself when boat speeds toward plane, the problem is most likely cause by aeration of the transducer. This may be verified by configuring the ping OFF for each of the RealVision 3Dâ„¢ transducer's supported sonar channels and then testing the system. We have a concern the that proximity of the transducer to one another and the larger size of the RealVision 3Dâ„¢ transducer may be contributing to the reported symptoms. Please respond with photos of the vessel's stern showing:
- the proximity of the transducers to one another
- the proximity of the transducers to running gear
- the proximity of trim tabs to the transducers
- the angle of attack for each transducer
- the bottom of the hull forward of the transducers