Review and Teardown of Radio Shack AM/FM Portable Radio

The Radio Shack “Digital AM/FM Pocket Radio” looks great on paper and I really want to like it. It’s everything I would have wanted in a radio 30 years ago: lightweight, digital tuning, stereo headset jack, speaker, great battery life, memory presets and an alarm function (To see all the features, check out the user’s manual)

Even with all these features, the unit’s few weaknesses limit how and where this radio can be best utilized. The most glaring issue is poor audio quality via the tiny internal speaker. It is less than 1.5″ in diameter and delivers only ½ watt of power. I will explain why such a small speaker is used (it’s not just due to size constraints) but the end result is a very tinny sound with almost no low end. It can become grating on the ears after a while, and making it louder only exacerbates this problem.

I’ve found that voice broadcasts are easier to listen to on this radio than music. That often means listening to news or sports on AM, however that reveals a second weakness of this unit: poor AM reception. The manifests itself as noise interference that’s difficult to eliminate but can be reduced somewhat by rotating the radio. Many AM radios suffer from this phenomenon, but I have owned radios in the past that were much better at rejecting noise, (even cheap ones) so it can be done! FM reception is pretty good, and it manages to pull in some non-local stations. It uses a wire inside the wrist strap as an antenna. Initially I feared that this would be a point of failure, but it looks like the wire is not exposed to undue stress under normal use, so I’m not too concerned.

Luckily, the unit has a jack that can be used to connect headphones or an external speaker. The sound quality is markedly better through this jack, but it still seems like the frequency response is not as great as it should be. Ideally, this radio would support Bluetooth connectivity. In today’s world it should be as ubiquitous as a headphone jack for any audio device. It would not add much to the unit’s cost.

What is the best use case for this radio? It’s barely audible in a noisy environment, so maybe it would work well for camping or quiet solitary use. Its light weight (only three ounces with batteries installed) make it ideal for carrying in a pocket or for travelling, but in today’s smartphone world, where’s the need? It’s probably best suited to have around for an emergency.

It looks like this radio is sold by many companies under a variety of brand names, (and in other colors) perhaps white-labeled by some manufacturer. Here are a few on Amazon:
Opening the radio is as easy as removing the two visible screws on the back and gently prying it apart.

Most of the radio is contained in the AKC6955 Integrated circuit chip. The datasheet for this device indicates that it can actually tune 20 – 230 MHz FM and 0.15 – 30 MHz AM, so this unit is only limited to the FM and AM broadcast band by the firmware. It also sports an integrated ½ watt audio amplifier, which explains the tiny speaker. Although a larger speaker could probably fit in the case, it could not be connected directly to the tuner IC. A larger speaker would require a separate audio amplifier chip and possibly an audio transformer, thus driving up costs.

The tuner IC is connected via I2c to an unmarked 48 pin microcontroller that accepts inputs from the various buttons and drives the LCD display.

Note the staggering amount of technology this radio contains compared to a pocket radio from 30 – 50 years ago. The microcontroller alone has more computing power and RAM than an early 1980s Nintendo game system.
There are four pads near the microcontroller chip labeled “VCD”, “GND”, “SCLK”, and “SDIO”. These would appear to be programming points of some kind. I connected an I2C and SPI analyzer to these pins but so far I’ve not been able to detect any data. This could be one possible way to remove the tuning frequency limits on the device, or better yet reprogram it to play a game. I’ll keep trying and report back here on any progress.

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