[Lowfer] A question about NDBs

[Dave Maples]

All: Time for some very ignorant questions:

In the long ago, I used to listen to NDBs on an old BC-348 receiver.  All
the NDBs used ~1000-Hz MCW on an AM carrier.  Recently I have begun tuning
through LW again, and now I find both the MCW beacons and other beacons that
ID in straight CW, and then hold a carrier for a bit, then repeat.

1. Since both types of NDBs seem to be aeronautical, I'm puzzled as to how
many ADF installations can deal with the non-MCW beacons.  Do they now
contain BFOs?

2. When did this type of beacon start deploying?

Thanks,
Dave WB4FUR