When it comes to signal processing, there are a couple of issues that top the priority list: generation and decoding. This month we’ve gathered some excellent projects that address these issues with a mindset toward effectiveness, efficiency, and frugality—three equally important considerations. In discussing their projects, the designers detail their experiences and provide insightful guidance for those of you who want to follow their steps.

Even if you have access to a high-priced signal generator at your office or laboratory, chances are you wish you had one at home too. Accessibility to professional-grade generators comes in handy, but traveling to another location during business hours isn’t always convenient. Neal Martini decided to take a crack at building his own RF signal generator around a Microchip PIC16F877A microcontroller and an Analog Devices AD8367 variable gain amplifier (p. 12). He admits this project wasn’t easy, but the challenge was worth it. The result is an inexpensive RF signal generator that’s comparable to commercial products.

Gordon Dick also saw the value of having his own signal generator—more than one, in fact (p. 32). Gordon’s particular need was for a second square wave source. Using a Microchip PIC16F876 microcontroller and a Linear Technology LTC6903/6904 oscillator, Gordon designed a low-cost alternative to off-the-shelf generators.

There are times when you need dedicated tone decoder hardware or digital signal processors for single or multi-frequency tone decoding, but acquiring the equipment can be difficult. With an efficient and well-designed algorithm, Eric Kiser tackled the all too common problems of lack of funds and space (p. 22). Although it’s based on the Goertzel algorithm, Eric’s algorithm does not involve floating-point operations.

We trust you’ll agree that these projects are both exciting and useful. No doubt you can put these designs to good use on your own workbench. And the affordability of each makes them ideal solutions regardless of your budget.

This month we also have a number of other terrific articles, including an intriguing article about Bob Armstrong’s effort to build a functional equivalent to a CDP1861 video controller chip (p. 58). He replaced random logic using programmable logic devices. Specifically, he used two Atmel ATF22V10 GALs and two 74HC chips to accomplish his goal. Now, Bob can play video games on the replica of the COSMAC Elf that he also designed himself. Although it’s definitely an interesting project, you might not plan on building your own version of the Elf to use this solution as it was intended. No matter. Either way, you’ll find Bob’s coverage of using PLDs to replace random logic greatly useful.

jennifer.huber@circuitcellar.com