Description:
A Short Wave Receiver based on the MK484 (formerly ZN414) that includes the
tropical bands and 49 metre bands.
Circuit Diagram
Circuit 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.
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