Radio receivers going digital
And it’s not about digital radio
Japan is getting behind on digital radio technologies. Chinese products are getting far ahead. I’ve dumped most of my Sony collection lately; they were very good but not good as the modern full DSP radios.
I’ve been brought up with a bunch of Japanese radio receivers. Most of them were Sony products. ICF-5900, released in 1975, was one of my favorites and I still believe it’s one of Sony’s best designed receivers. While I don’t own one anymore, I still love the design.
I remember that the sound of ICF-5900 was heart-warming and it also worked very well on listening to the shortwave stations. The radio was big like a university textbook because there was very few integrated circuit (IC) chips there inside and most of the parts were hand-assembled discrete devices including the transistors. I really loved the radio and I carried it all around where I went during my early teenage.
Until early 2000s, Sony was doing pretty well on designing the all-round radio receivers. ICF-SW7600GR is (unfortunately) the last receiver released in 2001 as a part of paperback-book-sized shortwave radios since ICF-7600 in late 1970s. This receiver has a look of digital radio; the local oscillators are phase-locked-loop (PLL) driven and well stabilized, and computer controlled. This radio is not, however, truly digital; the signal detectors are not much different from ICF-5900, though it can decode the stereophonic FM modulation which ICF-5900 doesn’t. I listened to a lot of shortwave stations while I was in a hospital on May 2002 for recovering from the immune system damage caused by massive allergic skin destruction.
One of the technical incompetence in the 2010s I’ve found is that Japanese consumer radios are getting more behind to where the bleeding-edge technology is. The fact that Sony no longer releases new radio receivers with the state-of-the-art technologies is only an example. Most of Japanese manufacturers have already outsourced the radio engineering design to outside Japan, and many of then are made in China. I think this decision is rational, regarding the cost of making new radios solely in Japan under a fierce price competition.
On the other hand, in a non-consumer market such as the amateur radio transceivers and communications receivers, Japanese manufacturers still have the major portion of the market, while maintaining the competence of the cost performance. ICOM’s IC-7200 is one of my favorites; its signal decoders are made of digital signal processors (DSPs). While maintaining the traditional superheterodyne design of converting higher frequencies into the intermediate frequency (IF) for easier and stable decoding, introducing the IF DSP as a part of hybrid design has been a mainstream for amateur radio products for many years, though I haven’t seen this type of design in cheaper consumer radios.
On the other hand, some creative radio manufacturers are going more digital than IF DSP; Elecraft’s KX3 introduces direct digital conversion of received/transmitting signals from the audio signals to the radio signals up to 54MHz. This type of full DSP architecture, also known as software-defined radio (SDR), has a significant advantage from the past analog and IF DSP architectures; the radio needs smaller number of chips for more features, less tuning points for more stability and the ease of manufacturing, and more mathematically simplified and clear cut ways of signal generation/detection applicable.
One of my recent discovery on consumer radios is that quite a few radio-receiver chips are already available and some manufacturers have already made the products with those chips. Silicon Labs’ Si4734 is one of those chips which requires very few parts outside the chip; it directly processes all available broadcasting radio frequencies and modulations by the internal DSP. You can make a one-chip AM/FM and shortwave receiver with it.
I’ve got a PL-310 from TECSUN, a Chinese manufacturer, which employs the Silicon Labs’ chip, for less than JPY6000 recently. I immediately find that PL-310 is quite different from the past analog or hybrid receivers on the reception sound; the sound coming out from the radio is very stable and requires no manual tuning-in for a better sound. And the sound is crisp. This is similar to the difference I felt a long time ago when I compared the sound of the same songs between the compact disc and analog vinyl recordings. Phase and group delay nonlinearity affects a lot to the quality and fidelity of the signal.
Please do note that in this article I am not writing about the “digital radio”, which actually stands for the digital-modulation-based broadcasting based on popular streaming technologies such as MPEG Audio and OFDM; I am writing about how traditional radio using amplitude and frequency modulations can get even better by introducing a digital technology on the receiver side.
I should also note that on the transmission side, most commercial broadcasting stations have already gone digital since a long time ago. From the audio mixers to the modulation unit of the transmission sites, I believe all signals are processed in the digital domain as a time-series numbers, so long as I’ve read from broadcasting technology articles available in Japan.
I do not deny desire of making old radio collections by the radio enthusiasts. The old receivers and transmitters have their own beauty and sense of operation which newer transceivers do not have. And I understand some people do not like the sound of digitized receivers for subjective reasons.
I think, however, taking a look for a new technology and experiencing it are far more enthusiastic than staying on the old technologies.
I sold most of my Sony analog radios to a second-hand reseller.
And I feel sad that my country Japan has already been getting far behind on consumer radio engineering and technology.
