will be starting new layout- 4ftx9ft in nscale. have locos from previos layout. if you keep the loop isolated can you safely run dc on the loop and run dcc on rest of layout?
If they are separate blocks (i.e. both rails are separated by a gap or insulated rail joiners) or are completely separate loops that don't connect then yes you can...however you need to be careful, as a mix-up causing an engine to say go thru a switch and bridge the gap between DC and DCC could cause considerable problems.
A better choice might be to install a DPDT switch between your DC power pack, DCC controller, and the layout, so the layout is either all DC or all DCC. Many of us did that when first adapting an existing DC layout to DCC, and some folks like to keep that option so they can try out new engines before installing a decoder, or so when DC friends come over they can bring a guest engine along.
I would advise against it, or at least not using only a gap. The DCC-powered engine can cross over a gap to DC powered rails, resulting in both running through the decoder and back to the DCC system. Poooffffffff!!!
I wouldn't do that. Even if you run completely separate loops, with no tracks between them, one of these days you'll add a siding, drop down feeders and connect them to the wrong bus. You will quite likely be in the market for a new DCC system.
Once you start running DCC, you'll probably realize that the only reasonable path forward is to install decoders in your DC engines, or sell them and buy DCC replacements.
It takes an iron man to play with a toy iron horse.
pabdoif you keep the loop isolated can you safely run dc on the loop and run dcc on rest of layout?
I have a little set of loops set up that way, and it makes me as nervous as a long-tailed cat in a room full of rockers. Don't do it.