Fish Finder – Sonar RFI Kit
Fish Finders/Sonar units can cause RFI “noise” in other electronic devices on a boat including audio and video systems, radar, SSB, wind/speed/depth instruments, etc. Likewise other electronic devices can also interfere with the fish finder and cause erroneous depth/temperature readings.
Palomar Engineers has developed a simple to install fish finder/sonar RFI suppression kit to solve the RFI noise problem aboard recreational and commercial boats.
Just slip a split bead on the transducer cable (1" ID) and use the 5 1/2" ID split beads on the fish finder/sonar readout unit transducer input and DC cables. Use the extra ferrites on other equipment needing protection like the Radar, radio, etc.
50 ohm coax to 75 ohm balanced output baluns are useful for low (< 1 wavelength) dipoles exhibiting 75 ohm characteristic impedance or for matching to balanced ladder line whose endpoint impedance is near 75 ohms.
50 ohm coax to 75 ohm CATV coax connections are easily done with a 1.5:1 unun with SO-239 connectors on input and output. Likewise 50 ohm coax to unbalanced verticals or loads near 75 ohms can be matched with a 1.5:1 unun.