I had problems using it at home also,,,,contacted Vexilar and this is what was saidDD-100 Not Working It would read 68 ft on low power but worked fine at the deepest depth setting in the air test.
So I emailed Pat at Vexilar here is his reply
Properly testing the DD-100 depends on how your trying to get the
reading to show up. Testing it, through an air test, is 50/50 at best.
You have to do it a certain way with different sonar's to get a depth
reading and it still isn't easy to do. The DD-100 is not designed to
work in air. Get it down to the lake and in the water (deeper than 3
feet) before you determine if it works or not. You need to get a
good/steady bottom reading before the digital depth will show properly.
6667 - West Old Shakopee Road
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