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Blackloud Releases Soundot FM Radio for Apple

AF-1 uses tiny headset tuner attached via Lightning port

For many in the radio industry, it has been a great frustration to see the wide acceptance of data phones with their powerful interfaces and networking capabilities. Through a combination of capital investment, brilliant design and innovative manufacturing, the data phone has become nearly ubiquitous and revolutionized our telecommunications infrastructure.

At the same time, Apple Corp. has declined to develop a method of using its popular iPhone — over 1 billion sold worldwide since 2007 — to play out over-the-air radio stations as part of its wide range of capabilities (streaming is possible; for example the iHeartRadio app). Some observers say this is because Apple makes a profit on its own music-on-demand services. In 2013, Apple launched iTunes Radio, a service that seems designed to replace commercial radio and that is now known as Apple Music Radio.

Consumer demand for a radio in their iPhones has always been present, and it appeared to peak in 2017, when the head of the FCC itself called on Apple to “do the right thing” and enable FM radio in their phones. This request was based on outside analysts’ suspicions that it was potentially as easy as a software download to activate an existing internal communications chip.

Apple responded to Chairman Pai shortly after, saying it had removed FM capability from its internal chipsets years earlier and that even the world’s most valuable consumer products company couldn’t make it work. And, well, no one could force it to try. If Apple didn’t want to. Good talk.


Yet some who love their iPhones saw good reason to have a radio capable device. For one reason, it permits very efficient listening to the existing FM infrastructure. FM is free and does not require using a contracted streaming service that charges by the amount of downloaded data consumed. Others have pointed out that even if 100 percent of the capacity of advanced 4G wireless systems were fully utilized to simply replicate the volume of drive-time live radio listening in a large city, the 4G systems would fold under the demand.

Not to mention the safety argument. Repeated failures of wireless data services in the aftermath of large storms have demonstrated limited reliability in an emergency. FM broadcasters with their in-house engineering staffs dedicated to maintaining one or a few large transmitters are often better prepared to provide news and vital information to large populations in an emergency. Portable devices, including the iPhone, are ideal emergency radios because they are easily recharged with access to even a small generator and have batteries that will run for many hours working as a radio during times when the wireless networks are not functioning.

Of course, there are many rural areas that simply don’t have 4G service outside of interstate highway corridors or large cities. FM radio is an international standard available almost everywhere.


It isn’t hard to understand why I have been interested in Blackloud’s development of the AF-1 to bring FM radio to the iPhone. I love my iPhone, too, and I can’t imagine getting through a typical day as a broadcast engineer without it. But radio is still a relevant and powerful service which is available to everyone for free. When I was offered a chance to review an early release model, I jumped right on it.

I have been running the Soundot AF-1 headset, complete with FM service, through its paces for about 15 days. I’m pleased to report it’s quite a good radio. In my attic (where I do my writing), I could pick up about 29 individual stations, some of which were NCEs and some of which are even out-of-market (e.g., from Providence), in addition to all the Boston-licensed Class B commercial stations.

The radio chip itself, the Si4705 developed by Silicon Labs, is tiny. In the photo of the iPhone with the headset plugged in on page 1, the radio module is the 2-inch red cylinder that forms the splitter to the two earbud cables. The chip itself is about 1/8-inch square (3 mm). The antenna is derived from the headset cord.


To operate the radio you must first download the free app, which you can get in the App Store by searching for “AF-1” or “Soundot.” I was able to install it and get it running in something less than five minutes.

The main screen features a “tuning dial” in the center that can be spun up or down the radio dial, mimicking the classic tuner knob on a car radio. Tuning is very rapid (there is no need to establish a server connection and initially buffer an audio stream) so that you can move between stations instantly. Favorites can be dragged down to buttons at the bottom of the screen for quick selection. There are tuning “seek” buttons if you don’t have favorites. It’s so easy to use that I figured out all the controls in just minutes, without having to read any instructions.

Volume control is done via the hardware buttons on the phone used to set the ringer volume or via a small switch pad in the headphone cord. Once the radio is playing you can turn off the screen and put it in your pocket and it will continue playing until manually turned off.

Over the course of several hours of listening to the radio I estimated that on my phone I would at least get 20 hours of operation without needing a recharge. Based on the age of the phone this may vary somewhat.

The AF-1 is fully certified as compatible with Apple devices such as the iPhone or an iPad tablet. It was developed to work within the world of Apple products, not as a “jailbreak” or hack.


Modern consumer electronics can fit quite a lot into a small package these days as the accompanying block diagram (above) shows. Not only does the AF-1 include a radio chip, to work with an Apple device it must include other ICs specifically designed to adapt to the Apple Lightning interface. The reference design was developed by Tempo Semiconductor as shown.

Included in the app is a five-band (soon to be six-band) equalizer to allow customization of the sound to individual tastes or by station. The bands run between 50 and 5 kHz (10 kHz).

The current version of the radio app does not allow display of the RDS messaging with the essential Artist and Title fields used by music stations. It turns out that this capability is part of the Si4705 chip and adding RDS can be achieved by an upgrade in the app. The new version is in beta test. Blackloud generously let me try the beta version of the app and indeed it picks up the RDS messaging on stations all over Boston. It adds a nice visual element to the radio that many of us have come to expect.

A few years back, I remember a small portable radio that was offered to stations as a premium for listeners. I can imagine the AF-1 would make a nice station giveaway item, and in the process, it would promote FM radio to many people who would like to have it but can’t obtain it on their phones. Perhaps it would also help to introduce a new and younger generation to radio? Only time will tell.

Blackloud announced the AF-1 was available for purchase as of mid-September. The CF1 FM Headset for USB Type C Androids is expected in 2019.

Comment on this or any story to [email protected].

Michael LeClair, CPBE, is manager of broadcast systems at WBUR, Boston and former editor of RW Engineering Extra.



Blackloud has a radio affiliate program to encourage stations to promote the headset.

Stations that join at the company’s website receive a code that’s unique to them, which they share with listeners. Listeners get a 10 percent discount off the AF1 FM Headset, which retails for $79.89, after entering the code and purchasing the headset on Affiliates earn a 15 percent commission on sales associated with their code.

Blackloud also offers an affiliate program for webstore owners.