Thursday, December 4, 2014

The Chinese Pixie 2 QRP Transceiver-An Asian Twist On An Old Favorite

Many hams have read about, heard about, or even used/owned a micro transceiver that is the essence of simplicity itself.

The radio I'm referring to is the much loved AND reviled, and misunderstood "Pixie 2".

The origins of this radio are familiar to the ardent QRP enthusiast.  The original radio, called the "Foxx", was invented in 1982 by George Burt, GM3OXX.  It was a simple, 5 transistor rig, that produced a WHOPPING 2.5 watts of RF on 40 or 80 meters.

Soon after, Oleg Borodin, RV3GM slimmed it down by eliminating one of the amplifier transistors and a few other "non-essential" components.  This, of course, became the "Micro-80" transceiver.  This radio is the closest cousin to the Pixie, in that, the oscillator stage appears to be quite similar.

Finally, WA6BOY's version of the radio eliminated the transistor audio amplifier stage and used an LM386 I.C.  This is the version that we still "use" today...almost 20 years later.

The Pixie 2 can be breadboarded out of junk box parts, or acquired all at once from a few vendors that sell the Pixie 2 in kit form.

The first, and most widely known is the version available from Halted Specialties, or simply HSC.


I have built three of these kits, and NONE of them worked very well...or at all.  The last attempt was a 30m version.  The quality of the circuit boards is atrocious at best, and for the beginner, this kit is better left alone.  To call it garbage would be too much of a compliment.

Next is the QRPme kit that Rex Harper sells, the Lil Squall.

I have known a few people that have bought this version, and they really like it.  The quality of the kit is outstanding, and having a custom made enclosure included is top notch.  Rex stands behind his products as well.  This Pixie has the unique advantage over the other kits, in that changing bands is a simple as changing the daughter-board with the appropriate coil settings for the band.  Nice touch!

Next is the RadioKit Pixie, available on eBay from Yiannis Kontarinis in Athens, Greece.
I have no information on this radio, so I can't really say much about it, other than its cosmetics.  It's not as attractive as the Lil Squall, but it is still pretty sharp looking.

And FINALLY...the version available from DOZENS (and I truly mean DOZENS) of sellers in China...

These kits are called the "Shoes" in China, although I believe that has something to do with how the word "Pixie" is translated back into English.  It is the same two-transistor circuit, with LM386 for audio amplification.

However, there are a few nice changes with this particular version.  Firstly, this radio has a 47K variable resistor that allows for a few KHz of tuning around the crystal frequency.  While it was also something that is featured on the Chinese "Super-Rockmite"...and allowed the TRANSMITTER to also QSY a bit, this one is strictly for the RX only.  Next is the rather beefy BNC jack.  This is a DRAMATIC improvement to the typical RCA jack that is used for the RF connections on many Pixies.  And finally...my favorite thing about this radio is the PRICE!  I bought mine direct from a Chinese seller on eBay (although you can also purchase them directly through China's domestic shopping site, Taobao.com) for $7.59...and it was shipped FREE from China via China Post.  And there are many sellers that sell them for as low as $5.50 with free shipping. 

The true reason that I bought this Pixie was due to an unfortunate accident that I had with my Super Rockmite, which I have currently written about before.  I was connecting my Ten-Tec KR5 keyer to it, but after doing so, the RM went into a wild self-oscillation that quickly destroyed the 8W behemoth.  Being so close to Christmas, I wasn't able to afford to replace it.  That's when I saw the Pixie.

The radio was ordered on November 7th, and shipped out the next day.  The worst part of shipping from China is the wait times in Customs.  But ANY international commerce is rife with delays like these, and having purchased many things directly from the PRC, I was familiar with the wait time.  The radio arrived in Buffalo NY 11 days later, as expected.  

The kits all come in padded envelopes, and when opened....this is precisely what you get:

And that is LITERALLY all you get. 

NO instructions.  Nothing but your circuit board and a small baggie filled with parts.

In order to make this work, you have to do a little legwork.  That's why ALL of the schematics and parts lists are on the sellers' pages...and they ALL do it this way.  I like to think that it keeps the costs down by not having to photocopy instructions over and over and over again.

Back on the seller's page, you find THIS:

Thankfully, the English translation is on the parts list.  And with this information, AND the fact that the circuit board is marked with component locations (R1, D2, etc), it's not too difficult to get the components roughed into place and ready for soldering.

In addition to the parts as listed, I also ordered a 7.030 MHz crystal from Rich at ESS.  For $2.95, he sent the appropriate crystal for this rig.  For some odd reason, almost 100% of the CW rigs that you buy from China come equipped with crystals for 7.023 MHz.  As a General Class ham, I can't use 7.023, and I don't think I would want to...since QRPers hang out around 7.030-7.040 anyway.

The rig goes together fairly quickly, however, it must be noted, as it is on a recent YouTube video describing this rig, the kit comes with A LOT of extra parts...parts you DO NOT NEED.  I don't understand the reason for this...perhaps the person putting the kit together ran out of needed values, and added a bunch of stuff as a "good faith" gesture...but this just adds to the confusion.  As in the video, I too, had to add my own resistors...a 1K and the 33K to be precise.  They did not come with the kit.  THANK GOD Radio Shack still sells some components.  In the meantime, while not wanting to wait until I got to RS to buy some 33K resistors, I simply paralleled 3 of them at 100K ohms per...and it worked just fine. 

The solder pads underneath the board (and it's a through-plated board...nice touch) are tiny, so a small iron is a necessity.  I have an 18-watt iron that has a tiny pencil tip that saved the day.  You WILL need a larger iron for soldering the coaxial power jack, both of the 3.5 mm jacks (key and audio out) and the BNC male RF jack.

Total build time was just under and hour.  Your mileage may vary, depending on your comfort with a soldering iron and how much light you have in your work area.  I say this because some of the components are TINY...and the markings can be difficult to read.  At 42, I am beginning to wonder if I may be needing bifocals soon.

After nipping off the soldered leads under the board, I connected my antenna and earbuds (iPod style work QUITE well in this little radio) and then the power...and was delighted to hear 40m spring to life.

The audio is TYPICAL Pixie 2...it's as wide as a barn door...but the sensitivity is actually very good for what this little toy is.  If you've ever used an old Heathkit HW-7 (with the 40673 for the detector), it's comparable...except there are NO microphonics.  

When using this, or ANY Pixie that is using the LM386, a few things must be adhered to for the best possible performance.  For starters, using a power supply is not recommended, as you WILL HEAR HUM.  Write it in stone.  Battery power is where it's at with this rig.  And many like the idea of being able to use a 9V battery due to size, but the 9V doesn't supply enough current for the Pixie to both transmit enough power AS WELL AS not current starve the LM386.  Many hams complain of the buzz or motorboating sound when attempting to debug a misbehaving Pixie...and sometimes it's BECAUSE of not enough voltage/current.  Secondly, a good antenna is essential.  I was able to hear QSOs in progress and even be reported on the Reverse Beacon Network while connected to my Opek HVT-600 portable antenna, but with a proper antenna such as a dipole or an end-fed (such at the antenna I sue at home), the audio really wakes up.  

At my home QTH, I am 9.5 miles away from WGR550 AM's transmitting tower.  I was able to hear it when I had my HW-7, and occasionally I can hear it through the Pixie.  Some cures for it are to ground Pin 7 of the LM386 via a 10 uF capacitor.  I have done this and it works very well to mitigate the BCI interference.

On Monday night, December 1st, I made a few CQ's and was answered by N2BHA in Rome, NY.  We had a nice QSO, while I tried to contain my enthusiasm.  Sure, it's only 165 miles from point-to-point, but the fact still remains that it IS a radio capable of REAL communications.  I know that I will be installing this into a typical "Altoids" style box (although mine is a blue Newman's Own box...I like to be different) and also will be adding a a K1EL K-16BAT kit so I can use an Iambic A single-lever paddle.

In summation, this is a nice, BASIC, NO-FRILLS radio.

PROS:
-COST
-AVAILABILITY
-EASILY EXPANDED

CONS:
-BCI OVERLOAD IF IMPROPERLY GROUNDED, ETC
-LACK OF INSTRUCTIONS
-EXTRA AND MISSING COMPONENTS

73/72 de KB2HSH


28 comments:

  1. I'm pretty new to amateur radio in general. Could a person plug something like an 80 meter crystal into the Chinese Pixie and operate on that band as well?

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  2. You said you swapped the 7.023 MHz xtal with a 7.030. Did you have to make any other modifications to transmit/receive at 7.030 MHz?

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    2. Just bought one of these, and am wondering the same. You don't have to change anything on the finals to get the receive to work?

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    3. You can just swap out the crystals, as long as you're within the 40 meter range.

      I would keep the crystal(s) within the lower CW band plan. (7.000 - 7.125 MHz)

      Just be sure that you're using a crystal/frequency that's within your license class.

      Lastly, these little rigs are made for a band, so you'll need to only use the appropriate crystals for that band.

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  3. Another HAM and I bought those Pixie 4.1 kits on Ebay, and have successfully used them for QSOs, but we're also just a few blocks apart.

    I use a 1/4 wave 2 meter ground plan antenna build from coat hanger, and he uses his HF long wire antenna.

    Since these little boxes don't push hardly any power and I don't have antenna tuner (yet), using my 2 meter antenna has been successful.

    There is also an antenna tuner kit on Ebay you can get that I've seen some demonstrations for their construction and use and they appear to be worth the $mall investment too.

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  4. The Chinese Pixie - To use on 80 meters would require a xtal change and the L2, C5 and C6 be changed for the 3.5 Mhz band.

    The output transistor a 8050 is a better transistor than most Pixies. It is rated at 1 watt where a
    2n3904 which is used in many Pixies is rated 0.31. The 3904 does have higher breakdown voltages which might be better under high SWR. I kept the 8050. The osc transistor in the pixie is a 9018, almost the same as a 3904 except for breakdown voltages. I used a 2n3904 for the osc in the Chinese Pixie. It is a good buy I think I paid about $3.70 USD for the kit with free shipping. I do use cores I wind for my own coil and choke in place of the ones provided with the kit for L2 and L1. You can not expect a $4 kit to be as good as a nice commercial transceiver. But the Pixie are fun and if you have a decent antenna you will learn a lot and enjoy contacts. If you can make contacts with a Pixie, some day you will be able to work DX with your fancy transceiver. Primary weakness is in Receive. Buy a good receiver and put up a good antenna and you will work the world with low power. I have worked 42 states on 3.5 Mhz running a watt to an anteanna only 20 feet above the ground. Have Fun 73 Stan AK0B

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    1. Thank you for the breakdown pertaining to the Chinese nomenclature of the transistors. I tried doing some research on them earlier in the year, but soon became frustrated.

      I have found that when using the Chinese Pixie, a balanced antenna seems to help in a HUGE way. At the home QTH, I am using a PAR/LNR EF-10/20/40...this antenna is normally fantastic for anything I want to do...hell, I even load it up with the AT-100 auto-tuner for other bands...but the use of the coax shield as the counterpoise doesn't make the BCI problem any better. In the warehouse where my company stores all of its cable, etc, I have an INDOOR dipole...and this antenna is FAR better for knocking down the adjacent interference and overload.

      That's interesting that you also wind your own coils. I have read in other places where guys use toroids rather than the molded inductors...I bet this improves performance in a BIG way!

      73 de John KB2HSH

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  5. I did change the crystal on one of these Chinese Pixies for 10140 kHz - and the reception of QRSS and WSPR signals was remarkably good. OK the LC circuit wasn't optimised for 10 MHz but it did work on RX. There is the Frogs version which has more output and uses an extra crystal in the receiver path to help filter out unwanted signals.

    A simple 2-component audio filter: http://puebladx.org/download/18-Morse
    1uF and 47 mH for around 730 Hz filter OR 100uF and 1mH for ~500 Hz.

    Fancy changing band?
    Here are the output section values.
    Both filter capacitors are the same.
    160m =4.4 uH, .00176 uF
    80M = 2.23 uH, 894 pF
    30m = .79 uH, 315 pF
    20M = .57 uH, 226 pF
    17m = .44 uH, 176 pF
    15m = .38 uH, 151 pF
    12m = .32 uH, 127 pF
    10m = .28 uH, 113 pF
    6M = .16 uH, 64 pF
    Source: http://www.indianapolis.net/QRPp-I/pixie2_WE6W-info.htm

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  6. Have you investigated using LM386 pin 7 for muting and other aspects of the Pixie as described here:

    http://la3za.blogspot.co.uk/2003/04/using-pin-7-of-lm386-to-reduce-bci-and.html

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  7. Has anyone successfully converted the Pixie to using a DDS VFO, the way the March 2015 QST article does with the Forty-9er qrp rig?

    I have a Pixie, and would like to convert it rather than get a forty-9er

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  8. I'm thinking of using the AD9850 DDS VFO by the way.

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  12. Got the Pixie working so deleted previous posts. Wide as a barn door but nice kit and went together nicely -- 3 caps extra -- not sure why.

    Have fun.

    73, Bernie VE3FWF

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  13. Any progress using a DDS BFO.

    73, Bernie

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  14. Really needs a band pass filter with a reasonable Q. Anyone built one yet?

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    1. Hans Sommers at QRP-Labs has one for about $5, or you could follow his design and fab your own.
      http://qrp-labs.com/bpfkit.html
      VY 73,
      Wes AE6ZM

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  15. Wes
    Looks like that filter would work well Not too sure where to insert in the Pixie RX path.

    Anyone tried this filter on a Pixie?


    Regards,
    Bernie

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  16. I have ordered two band pass filters. -- one for 20 and one for 40. Looks like a nice cost effective product.

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  17. I read that putting a 1uh choke across the antenna terminal helps eliminate BCI.

    Works remarkably well and the TX output did not seem to be reduced. Will test and advise. Not sure what a circuit simulator would say regarding this simple mod.

    73, Bernie

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  18. Works very well -- no BCI. Output measures 1 watt.

    73, Bernie

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  19. I built mine and receive works, but cannot see any output on my WM-2 wattmeter. I do hear the note in a receiver in the room.

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  20. You will hear the XTAL oscillator as it on the same frequency as the TX. My Pixies draw about 1 ma on receive and about 18 ma on transmit. The RF output is about .75 watts. Double check that the output transistor is installed correctly

    73, Bernie

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  21. Has anyone successfully converted these kits to an AM talking Pixie? Or replaced the Crystal with a resonator and variable capacitor to gain the ability to tune around the band?

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  22. The Pixies can decode SSB. The ability to move the TX frequency is really a must with these rigs -- at least be able to pull the TX frequency +/- 1 KHz.

    73, Bernie

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