Old square nails can ring up pretty good, even on the NOX depending on orientation. This is where raising iron bias can be helpful, or just hunt in Park 1 which has some iron bias built into it.
I have a house I hunt from around the same time period and it is very challenging. There are just too many layers of trash and to much soil disturbence.
Here are some suggestions:
1. If Sanborn map or insuance maps exist for this location you might be able to determine where the older structures were that no longer exist.
2. Try using a small coil like a 5 inch or 6 inch coil.
3. Try using a concentric coil. Different search pattern and you can pick the top layer and miss some of the deep nails just by raising the coil.
4. For Equinox 11" coil, try using a high recovery speed and lower the gain. I have found that in Park 2 I can run the gain around 15 and use a recovery of 6 (or 3 on NOX 600) and pretty well cut out the deeper layer of nails beyond 5 or 6 inches. You may miss the deep coins, but if there is a half dollar or more modern coin above the nails you are more likely to get it.
5. Don't forget to detect near trees, large rocks, foundations, walls, under windows, near water sources, etc. Sometimes the best stuff is close to an obstruction.
6. Try to figure out where dirt has been disturbed and hasn't. Maybe they dug a line for septic in the 1920's or maybe more recently. That area will no longer have the "normal" distributions of artifacts. This could be good/bad depending on how it was back-filled.
Good luck and enjoy your Equinox. Just don't forget that a house site continuously occupied for 200 years is likely going to have a LOT of trash in the form of iron/aluminium and is going to be very challenging. Don't blame the detector or yourself if you don't find as much as you think you should.
I find coins but I may be missingsome cause Garrett aint no Minelab.
