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Simple interference fix for the Chinese Pixie
10 June 2017 | by The Chinese Pixie transceiver operating at 7023 kHz has become very popular. It often costs less than 5 USD on Ebay. Like most Pixies it is susceptible to broadcast breakthrough and intermodulation. Much of this is caused by the keying circuit of the audio amplifier, the LM386. The cure is to move the muting diode from the power supply pin (no. 6) to the bypass pin (no. 7). I have described this in another blog post with title: “Using pin 7 of the LM386 to reduce BCI and add side tone to Pixie 2“.
Here are two pictures that show how this can be done for the Chinese Pixie. One needs an additional resistor in the range 10 – 47 ohms. I have used 10 ohms in the picture. It replaces the old R3 of 1 k. The diode D3 is not mounted, and instead it is mounted under the PCB with the minus (denoted by the ring) connected to where D3’s minus was, and the plus side connected to pin 7 of the LM386.
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| R3 is indicated by the lower left arrow, and the old placement of D3 is shown with the upper arrow |
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| Arrow showing where D3 instead should be soldered. The minus, indicated by the ring, is to the left in the image |
3 Responses to “Simple interference fix for the Chinese Pixie”
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- Matt W1MST, Managing Editor
I got this Pixie as a kit with some other items and put it together using the kit directions but it did not work. I introduced some noise into the LM386 input and got a response but as a receiver, it just squealed. I tried a few fixes, even the Pin-7 fix, but still no workee.
Some years ago, I got the Pixie-II kit from Halted Supply (HSC). The PC board looked like something I had made on my kitchen table — it was adequate but far from being art exhibit quality. However, the little XCVR worked!
I added a cap in series with the crystal to give it a couple of KHz swing but did not try to do it so it only worked on transmit or receive. I sold it to a young ham beginner at the TenTec hamfest a few years back for $20 and he was happy to get it. The cap was an antique that was no doubt worth twice that amount.
I still have the 7023 KHz Chinese Pixie that I got that did not work for me. Anyone in the upper-48 that wants it is welcome to it — I have no time for chasing down the problem. Send an email to me with your mailing address and we can go from there. I’ll be interested to know what is the problem. I spent about an hour on it and then realized that I had better things to do.
My email is nocrud222 (at) yahoo (dot) com
Follow-up…
I have a taker for the Pixie. I was contacted almost immediately by someone who is in the process of getting his Technician license and has the General as a goal in the next step in his ham radio career. He’s an experienced electronic technician already so making the Pixie work for him should be a minor challenge.
I hope to see other Pixie-related and QRP items posted in this forum.
Bob — KK5R
Good to hear that it is on its way to a good home. It’s not a very good transceiver, no matter how much you tweak it, so I hope the person who gets it will very soon advance to something better!