Have 2 HB units and am using the 200khz(in some fashion) on both...Some my recorded tracts are all red indicating zero depths when i import them ...one HB unit can export a good tract the other not and successive tracts on the same machine can be good then bad without changing settings ....have made really good maps from the good tracts .....what am i doing wrong as i am losing half my data and thank you

If you power down a Humminbird before saving your tracks, it drops the depths to zeros. Before powering down, you must save the tracks (internal memory) and then you can move them to an SD card then or at home later. I lost a whole lake's depth data by not saving first. This will also happen if you have a power failure to the unit, even if it comes right back on. My power cord connection on the back of the unit came loose from engine vibration and I lost a half lake.