"KaitoWRX911" wrote in message
...
Why does FM and SW use whip antennas, while AM uses directional
internal ferrite-bar antennas?

HF transmissons may be reflected many times between transmitter and the
receiver. So the direction of the transmission is not so well defined.
Usually you don't have so good maxims and nulls with your ferrite antenna in
HF. With a piece of conductor you can have stronger signal.

Also the ferrite material is more expencive for higher frequencies than for
MF.
---timo