The MK484 basic AM broadcast band receiver kit 3 includes:
- 1 – Ceramic Earphone (Piezoelectric Earphone , Crystal Earphone)
- 1 – MK484 IC
- 1 – 100K Resistor
- 1 – 1K Resistor
- 1 – .1uf Capacitor
- 1 – .01uf Capacitor
- 1 – 788uh Loopstick Antenna Coil
- 1 – Plastic Variable Capacitor 60pf /141pf
- 1 – AA Battery Holder
MK484 Kit Number 3 has a 788uh coil with a center tap.
The MK484 Kits are TRF ( Tuned Radio Frequency, Tuned RF ) type receivers. This the most basic type of radio receiver with no regeneration or re-genitive feedback. The variable capacitor and antenna coil form a “Tank” circuit that tunes the radio stations frequency then the MK484 amplifies the radio stations radio frequency then “Rectifies” (Converts to Audio) it then amplifies the audio and powers the Earphone.
Yes a real MK484, not like other sites that sell MK484/TA7642. If you see this designation on other sites you are getting a TA7642 not a MK484.
The center tap should get better selectivity and decreased chance of overloading the IC. Or can be connected using the end of the coil, this lets you experiment with coil taps. You can also connect the variable capacitor Pin “A” to Point 1 and the MK484 input Point “3” to Point 1 also and leave the end of the coil Point “2” unconnected to cover the mid AM band from about 740 KHz about 2.2 MHz just a little into lower shortwave bands.
The alternate circuit diagram for the MK484-Kit-3 is to show the different RF input connection options. You can try short antenna connection at 1, 2 or 3 or wrap about 5 turns of small gauge wire around the ground end of the ferrite rod and connect one end of the 5 turn coil to an antenna and the other to ground. A common ground to circuit is not needed.