When restoring one of the antique radios, the final step is what we call alignment. This involves injecting radio signals into various internal stages of the radio and adjusting various controls in the circuit for peak performance. This normally involves a bank of equipment – a signal generator, voltmeter, and oscilloscope. Rather than maintain all of those, I designed and built a small computer controlled device that is an all-in-one solution – CompuLign.
The device uses an Arduino micro controller, 2 signal generator boards, and measurement circuitry plus a display for controlling the settings and seeing the output display in a mini oscilloscope fashion. I offered the device design up freely available to my friends on the Antique Radio Forum and several of them built one for themselves.
At right is a sample display for one of the alignment steps. This is a setup to align the IF transformer stages to peak performance at the required 455KHz frequency. The waveform shows that during a sweep of frequencies, the radio is now aligned to give peak response right on the target frequency. I won’t give much more detail here, but the user manual gives the full theory of operation plus detailed steps on all modes of operation.
The full design including circuit schematic, board design and Gerber files for production, and software are all freely available. I make no warranty expressed or implied, but only state that I have used this for over a year now. I do not offer units fully assembled for sale; that is not a business I want. But rather this is offered to fellow hobbyists to build, modify, or tinker with.
All of the code and the full user manual are available on the GitHub repository where it can be viewed and/or downloaded.