Single Transistor Receiver and Transmitter Design
Rolf Heine, DL6ZB





Weekend Project:
Single Transistor Receiver - Regen Receiver for the 30m Band
A 10 Parts "DX Receiver" 

The next idea after the successful construction of a single transistor transmitter for 30m was to try an simple 30m regen receiver with best possible performance. 

This receiver is surprisingly sensitive. It's performance is far better than I had expected. When I connected the receiver to the antenna the first time, I hardly believed what I heared! With just one transistor this little thing was able to hear everything - loud and clear. Listen to an audio file here:  audion.mp3

A word about the frequency stability. The receiver frequency depends on all parts of the circuit, even a swinging wire antenna and a matchbox, because all parts affects the Audion frequency. This is a tribute to the extreme simplicity of this kind of receiver. Stability and performance may be significantly increased by using a buffer pre-amplifier at the expense of a more complex circuit. If a pre-amplifier stage is used it is necessary to shield the regen stage from the frontend.
SIMPLE DX RECEIVER VERSION 1SIMPLE DX RECEIVER VERSION 1
SIMPLE DX RECEIVER VERSION 2SIMPLE DX RECEIVER VERSION 2
CIRCUIT DIAGRAM
The circuit diagram shows the complete Regenerative Receiver schematic. The tickling capacitor is tuned to about 30pF. The variable resistor R2 is tuned so that the RX draws a current of about 150 µA. A frequency counter for alignment of the circuit is very useful, although a broadband receiver as a helper to find the RX frequency will be fine.

It is very important (!) to use Hi-Z (~2-4 kOhms) headphones, otherwise the circuit won't work. Use a little AF transformer with a suitable Z-ratio if you don't have a Hi-Z headphone. I use very sensitive ancient 4 kOhms headphones which I found on ebay. The variable resistor R2 is a 10 kOhm fixed in version 2.

When using a 9V alkaline battery this tiny receiver will work for up to 3.000 hours (150 µA current). It runs pretty well with a 9V battery.  (usual 6LR61 type). 
Regen Receiver
Single Transistor Regenerative Receiver

SIMPLE DX RECEIVER



Weekend Project: 30m QRPP
Single Transistor CW Transmitter

Our local electronics dealer recently offered 10.111 MHz crystals (sold out). A few parts around it...

Output is approx. 300-400 mW. The 2-crystal version allows increased frequency tuning. See the red lines on the Reverse Beacon Network map at the window below.

Even W3LPL at a distance of 4200.2 mi (6759.6 km) heared the 300 mW signal on 10114.2 kHz from Germany with a signal quality of 7 to 9 dB SNR. This corresponds to a relative distance of 14 mi/mW or 22.5 km/mW !

The decoupling at the collector is essential to prevent tx chirp. This transmitter produces a clean chirp-free signal.

I used a 12 V battery as a power supply and a 2x30m random wire inverted-V up 25m above ground level.

Here are the first 3 QSO's made with the 300 mW QRPP:


30M  F5LBG    F   CW  Bernard  579   579   01-Dez-2012 11:27
30M  ON4MB    ON  CW  Walter   419   599   01-Dez-2012 14:29
30M  OH3HTR   OH  CW  Kari     539   589   01-Dez-2012 15:02

30m QRPP TX VERSION 1
30m QRPP TX VERSION 2

30m Single Transistor QRPP