05 September, 2014

So you want to play with a Pixie 2?

My own surface mount version of the Pixie2
Here's a guide in table format to minimalistic single-band amateur radio transceivers. The Pixie 2 and related kits are fun to build, yet they perform well enough to be used, although with some effort, for real contacts.

The idea of using the power amplifier transistor as a mixer seems to come from George Burt - GM3OXX - whose five transistor FOXX was described in 1983 in SPRAT. The basic design of the oscillator, PA/mixer and the simple keying has been more or less unchanged since Oleg Borodin - RV3GM - described the four transistor Micro-80 in 1992 in SPRAT. Then Dave Joseph - WA6BOY - replaced two of those transistors with the LM386 audio amplifier in the Pixie 2 (QRPp 1995). Most later versions are variants of these designs.

Here's the table of Foxx, Micro 80, and Pixie 2 kits:

Foxx


Foxx-3 kit from Kanga, £29.95
Incorporates a sidetone oscillator, changeover relay and low-pass filter. Different versions for the 80, 40, 30 or 20 m bands

Micro-80


Kit from QRPme, $35.00
Micro80D.
Updated version with choice of  high or low impedance headphone, polyvaricon tuning cap and board mounted connectors, 80 m.

Pixie2


Kit from HSC Electronic Supply, $14.95
For 80 and 40 m.
Eham review

Kit from Kenneke, $29.95
Includes 80 m crystal

Kit from QRPme, $40.00
Lil Squall Transceiver ][.
Several components and the output low pass filter are on sockets. Comes with a crystal for 40 m.

Ali Express Ham Kit Shack 40 m, $15.07 $10.49
40 m version. Tuning pot for VXO.

Radi0kit, £22.00
Enhanced Pixie2 which comes in 80, 40 and 20 m versions. Judging from the PCB layout it has my improved pin 7 muting circuit with less broadcast breakthrough.

What can I say to characterize these designs? On the one hand they are very simple to build and get to work. On the other hand they are also simple in the sense that they do not always perform very well. Therefore I don't think I would recommend them to any novice ham. It takes some understanding of frequency offsets and sidebands in order to make real contacts.

But lots of people have had great fun with such a minimalist transceiver which in its basic version puts out some 2-300 mW. And it encourages experimentation and modifications. Also, it should be remembered that it isn't really necessary to get a kit, as the Pixie 2 is quite simple to build from scratch also. I did that myself to try out surface mount technology.

The original designs and many variants and modifications are documented in the Pixie file document of SPRAT. There are many, many more clever modifications out there and I have my share on this blog also. To sort out and link to all the other pages is too daunting a task, so therefore I have focused on kits here. I would also appreciate comments if you think that something is missing from the table.