A 2 Transistor Transmitter Powered From a 9V Battery

A couple of days ago I built a simple 2 transistor transmitter on a small piece of PCB material. I used the style of construction that seems to be becoming my default – Manhattan-style using MeSQUARES from QRPMe. Rex is out of stock as I write this, but expects to have them back in soon. It’s definitely easier stuffing a ready-made PCB with parts and soldering them, but you don’t get as much of a feel for the circuit as you do by by building this way. With Manhattan construction, you can look at your build at any time and easily visualize the schematic. It’s a lot harder to do that with a circuit built on a PCB.

This is a simple project – it’s a version of the Pixie 2 as implemented by W1FB. I didn’t want the receiver part of this transceiver – just the transmitter, so it simplified construction even more.  I won’t go into any lengthy descriptions this time. You can relax – it was a pretty straightforward build. Here’s what it looked like when finished. See the resistor with the red lead attached to the top? Just behind it is a micro-switch that can be used to key the transmitter, though I prefer to plug in my AA0ZZ keyer from 4SQRP:

The slide switch is a DPDT.  One pole switches the antenna between the TX and the outboard RX.  The other pole disconnects the 9V supply on receive so that you are not listening to the crystal oscillator (which runs continuously) when trying to hear the station you are working. I teamed it up with my pride and joy, the WBR Regen Receiver and the first QSO was with Greg AK7Y in Alpine, AZ – a distance of 781 miles. He gave me a 449 – not bad for a transmitter that was only putting out about 170mW – that’s 0.17 watts! (Incidentally, when the power supply is 13.8V, it puts out about 430mW.) I  must admit that listening with the relatively wide bandwidth of the WBR was a test for my operating skills, and I might try using my Softrock Lite II receiver next time with the filter set to narrow. Nevertheless, it felt good to be using such a simple transmitter-receiver combination. Even better – this first QSO qualifies me for the 1,000 miles per watt award!

For a long time now, I’ve wanted to be able to send out a QSL with a hand-drawn schematic of the transmitter I was using on the back, and this was my chance. Here’s the back and front of the QSL I’ll be mailing to Greg on Tuesday:

Reader Erwin pointed out in the comments below that the oscillator stage is missing an emitter resistor. Unfortunately, the QSL was sent out a long time ago, and it is too late to correct that but for anyone wanting to build this circuit, please note that there should be a resistor of about 1.5K value in the emitter lead of the first transistor. Thank you for pointing that out Erwin!

Of all the QSL’s I’ve ever sent, this one feels most in the true ham radio spirit.  I’d like to think my radio ancestors would be proud, though if they were alive today they’d probably be running Flex radios 🙂


11 thoughts on “A 2 Transistor Transmitter Powered From a 9V Battery

  1. Looks great Dave – as always. I know the recipient of the card will appreciate the craftsmanship that went into the rig you used to work him as well as the card that confirms it.

  2. Truly beautiful construction! Keep up the wonderful work my friend! I enjoy G+ too, a link is on my website if you’re interested. I’ll keep watching your site for emerging projects!

    1. I’ve seen your blog Scott – was reading your post about the AVR AM transmitter just the other day!

      My construction projects look quite pedestrian in real life. I think it must be the lighting and close-up nature of the pictures that is making them look good! After I’ve modded them a few times and used them a bit, they don’t look quite as shiny and new 🙂

  3. Dave,,, My pleasure working you last night on 40m with your robust 500mw! After our qso, I worked K7NA, Vince on Whidbey Is., WA, who said he was copying you 559 as well. We were fortunate that the band was quite quiet up here in the PNW last night. Noise was only peaking around an S4, so that helped too.
    Jerome – VA7VV
    Vancouver, BC

    1. It was an absolute thrill to work you Jerome. You were my first QSO out of the US with this little TX, and the farthest QSO with it so far. Running it as separates with the regen makes me feel like an old-time radio op – especially when my sidetone consists of loud buzzing in my ears due to lack of RX muting (you can do that with QRP!)

  4. Hi Dave, I was looking for simple transistor TX circuits this morning when I came across your site, nice radio above, well done. But a comment you made about running out of ‘Stick on’ pads prompted me to think what else could one use without having to cut up bits of pcb so I came up with an easy idea for cutting the copper, I’ve now posted on YouTube

    It’s funny how one gets inspiration from a chance comment isn’t it.
    Anyway, I say that’s a lovely TX you’ve built there, blooming well done!
    Kind Regards … Andy gw0jxm

    1. Andy –
      I’ve been trying to comment on your YouTube video but I keep getting error messages. Will keep trying.

  5. Hi Dave, I’m glad you had a look at the video about the cutter, the next day I built a little two transistor FM TX using board with pads cut into/out of the board. Here’s a link to that video… http://youtu.be/QGcFAJHqXzs?hd=1
    By the way I only found your comment above because I revisited this site, it didn’t come to my email address, maybe I need to sign up or something? I’ll have a look at that.
    The other point is if you are unable to comment on YouTube it might be that you are trying to include a link back to your site or something like that, it doesn’t tell you what you’re doing wrong it simply says ‘error.’ Anyway as I’ve said to one of the YouTubers who commented on the video, ‘I believe in the butterfly effect’ and that remark of yours saying ‘Rex has run out of pads’ really got me started on something.
    73’s … Andy gw0jxm

  6. I really like the QSL with the hand-drawn schematic on it, but the oscillator circuit seems to be missing an emitter resistor.

  7. Is it possible to get a copy of thr 2 transistor “Pixie” transmitter in your website?
    I have lost the ability to construct because of diabetes.

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