A
Anonymous
Guest
We installed our 1720 in 1990 on the spreader of our boat mast...currently we have not been using the unit but recently found that after turning it on we get all the screen data, rings, lines, range change, etc., but we get no returns....we get "clutter" when adjusted in, we do get what we think is a return from the mast, which is about twelve inches away from the dome....that shows as a slight "blank" in the sweep background clutter....that has always shown in that manner....I read that we should clean the exterior of the dome....we have never done this for thirty-seven years only allowing "mother nature" to do the washing....would any excess dirt block out our echoes??? Any suggestions will be appreciated..