LW receiver with TBA120
The broadcast part of the long-wave radio spectrum (150 - 300 KHz)
contains a number of
transmitters with a highly stable carrier frequency like Droitwich and
France Inter.
This receiver was originally designed as part of an frequency standard for
use in the shack. At the time of building the junk box contained a TBA120
which contains the required limiting amplifier.
The TBA120 also contains a balanced mixer which can be used to build a
synchronous AM demodulator. This allows you to identify the station
the receiver is tuned to.
The carrier is available on pins 6 and 10 of the TBA120.
Loading one of these pins with an
emitter follower strongly influences reception. I still have to figure out
why. The frequency standard is still unfinished .....
Ferrite rods from a broadcast receiver contain a multi layer coil for longwave
reception. The parasitic capacitance limits the tuning range to
approximately 2:1.
Replacing the coil with a single layer coil gives a larger tuning range.
Archive containing the Xcircuit file (encapsulated postscript).