My radar overlay display can see a target on 6nm bụt it can not see on 4nm range

[linhkienbodam]

Hi,
My Furuno 1834C can see a targets on radar display well but on the overlay display, it can see the targets above 6nm range and can not see the targets under 4nm. What's happened with it. Please help. Thank you
Nick

 

[SilverKing]

linhkienbodam,

A couple of things. Try with your gain set to 75%. Also, what charts are you using? The chart does not seem to be displayed when overlay is selected.

 

[Sparky Wire]

Not having your IR filter set to high might help.

 

[linhkienbodam]

Hi,
I found the problem . I borrowed a Cmap from my friend and plugged it in, I can see the target under 4nm well, if I took the Cmap off, the target inder 4nm disappeared, I can see the target above 6nm only. This problem only happened on Overlay display. On the radar display we can see all ranges without Cmap. I tried to update my RDP149 but it seems the display didn't read my Update SD card (I think the SD card reader has no problem because it can read the Cmap well). I attached 149 updated file picture FYR
Thank you