Chris,
It could be a magnetron issue but lets not head in that direction until we need to. First there are some settings you may not have made it to yet as they are in the installation menu that you likely haven't seen. I'll walk you through getting in there and completing these setups properly as they have a huge effect on your radar returns. Before we do that though, here is waht I need you to do.
Power up your 1943C while holding down the "menu" button. Continue holding down the menu button until you see "Starting Installation Menu" on the screen. Once you see this you can release the menu button and allow your unit to fully boot up. Upon boot up, go to the radar screen. Once there, press the gain button and set gain to manual 50, sea clutter to manual 0 and rain clutter to manual 0. Set your radar to transmit, then do the following:
Press Menu
System Configuration
Installation Setup
Radar Setup
Make sure your Radar Type is set to "G". This is the proper setting for a 1943C.
Scroll Down to Tuning and press Edit to "On". This is on the right side of the screen.
Your display will now Tune the radar.
Once completed, scroll down to "Video" and Edit to "ON".
Your display will now adjust the radar video.
While you are in this menu press next page on the right side of the screen. Once on the next page note the total "ON" time and total "TX" time. This will help us determine how many hours are on the magnetron.
From here you can back out of the menu and go back to the radar screen. You should now see substantially more targets. You may have to adjust the gain up from the setting of 50 we started at. Get the gain set to a point give you plenty of returns. You can then adjust sea clutter to clear the picture up until you get it set the way you like it.
You should be good to go at this point. One item of caution. The tuning and video adjustment should be performed away from the dock, say a 1/2 mile of so from land. This will keep the radar from being overloaded by land targets during the tuning process and will ultimately result in a much better overall picture. Please let us know how this turns out.
Stickman