The Sudden Storm receiver from QRPme is a simple direct conversion receiver. The circuit is nothing new: A NE602 mixer with crystal oscillator for downconversion and a LM386 as audio amplifier. What is new though is the enclosure.
The parts for the sudden storm kit are being delivered in a tuna can. But the tuna can is not only a nifty enclosure for the parts, it also serves as the base for the fully assembled receiver.
The Sudden Storm receiver kit is available from [1] for just $ 35. The price is more than fair. The kit comes with a professional PCB and all parts to get started on the 40m band. Additional crystals can be purchased from QRPme.
Sudden Storm Receiver
This kit is ideal for beginners and can be build within a few ours. The receiver is fairly sensitive. Even though a fixed frequency crystal oscillator is used, the exact frequency can be adjusted with a potentiometer. The potentiometer acts as a voltage divider and the resulting tuning voltage is applied to a tuning diode in the oscillator circuitry.
Since the price and availability issues for a variable reactance diode (aka tuning diode, Varicap) have been a problem in the DIY community for a while, this kit uses two regular rectifier diodes for this purpose. Any diode changes its capacitance depending on the applied reverse voltage. A higher voltage yields a lower capacitance. This effect is optimized in tuning diodes but sufficiently existent in all rectifying diodes.
If you get bored of listening after a while you can add the Two Tinned Tunas transmitter, also available from QRPme and get started in CW.
Links and Sources:
[1] QRPme: http://qrpme.com/?p=product&id=SS4
Westerhold, S. (2012), "Sudden Storm (HF receiver in a tuna can)". Baltic Lab High Frequency Projects Blog. ISSN (Online): 2751-8140., https://baltic-lab.com/2012/08/sudden-storm-hf-receiver-in-a-tuna-can/, (accessed: April 20, 2024).
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