A Short Wave Receiver based on the MK484 (formerly ZN414) that includes the tropical
bands and 49 metre bands.
Notes:
The original data sheet for the MK414 states a maximum working frequency is around 4 MHz.
SW transmissions are so powerful that this receiver will work well with signals up to about
6 or 7 MHz. The 10k resistor controls the operating voltage for the IC which is critical
for good performance.
Coil Details:
The tuned circuit consists of a variable capacitor and fixed air spaced coil. For the
coil, I wound between 10 and 20 turns of wire on an empty tube of around 1.5 inches diameter. The
turns were spaced so that the overall length was around 3 inches. The variable capacitor
tuned 0 - 300 pF but there is plenty of scope for experiment here. One final point, you
will need an external antenna to receive broadcasts. I have an outside wire that is about 7
meters long and this was quite effective. The antenna can be connected at either end of the
coil or via a series capacitor value between 10pF and 100pF.
