Sometimes you have to make do with what you have. That means using tools that we have on hand differently than they way they were intended.
For instance this weekend I had to do an alignment procedure on customer's older rig that had a master oscillator and secondary oscillator that were out of calibration. The frequency counter in the workshop just didn't have the amplification required to pick up the low amplitude signals associated with those circuits.
It occurred to me that an SDR (Software Defined Receiver) has tremendous accuracy and ability to concentrate on a small bandwidth. This seemed ideal. So I hauled the laptop down to the workshop and connected a spare 'scope probe to the test point in the radio that needed the alignment. I didn't even have to connect the antenna terminal to the scope probe. I just wound the lead around a rubber-duck antenna on the SDR. The signal coupling was good enough to pick up a distinct hump on the spectrum.
It was easy to zoom into the signal and see when the oscillator was right on target for calibration. A little tweak on the calibration adjustment in the customer's rig and everything was back in tolerance.
There's no excuse for anyone to be without an SDR these days considering the price. The next step will be to get more familiar with GNU RADIO. Tools like this would allow a user to create more useful applications than just the standard SDR tuner. Why not a service monitor? Why not a deviation meter?
We will get one of our software developers on that right away....
73 and happy hacking...
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