Dave Richards AA7EE

August 9, 2011

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! 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 :-)

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