10 March 2008  |   

This simple and neat project comes from a excellent article of Dan Wissell, N1BYT, published in QST, August 2001, p.34-37. In a nut shell, the design of this receiver takes the advantages of a regenerative receiver (simplicity, sensitivity) and try to adress the issues which are antenna radiation, microphonics and hand capacity effects. The design uses a sort of Wheaston Bridge design for coupling the antenna to the tank circuit.

When building it, I tried to reach the smallest size and weight I could achieve, making it very convenient to carry.

WBR01

The construction uses the dead-bug approach: not very neat but very efficient to acheive a conpact design and avoid to develop a dedicated printed-circuit board for a unique realization.

You can see some foam on the cover arround the mini-speaker to improve the audio. You can also see the ferrit yellow core of the oscillator tank. I strictly followed the circuit published by N1BYT with the only exception of an additional AF amplifier stage that I found necessary to drive the mini-speaker (also built arround a LM386).

WBR02

The result is a very compact and leight receiver which I can carry very easily. I works fine with a short wire and the QRP Z-Match tuner descibed above (although the tuner is not an absolute requirement). With the components I selected, I can cover from 7.000 to 7.100 MHz with the 10-turn potentiometer. The frequency stability is excellent as well as the sensitivity: it is surprizing since it gives the feeling to decode signals sometimes better than by IC-735 (which is not a very good receiver !) in term of clarity. The only issues are the absence of ACG (a AF one could be added) and selectivity on CW band, which can be narrowed with the regeneration control knob but that could also be improved with a dedicated narrow band AF stage or a small DSP circuit.

In conclusion, I had a lot of fun in building this small project and it is always a pleasure to listen QSOs with it. I will always remember the face of a good friend of mine visiting my shak when this WB-Receiver was connected to an external amplified speaker: when he realized that the QSOs we were listening were going out of thisthis small box , he couldn’t believe it and asked me why I was having such big transceivers arround in the shak considering that a three knobs smatch box was sufficient to do the job ;-)