Guest Post: Joris’ home brew Si4835-based receiver

Many thanks to Joris van Scheindelen (PE1KTH)–an SWLing Post contributor from the Netherlands–for the following guest post:


High Tech AM-FM DSP Receiver From
AM FM ontvanger P3060601

The old mode AM is still an interesting mode for amateur radio communication, also in amplitude CW.

Building your receiver is not difficult and quite fun. The semiconductor industry makes interesting integrated receiver chips today that will be useful for an AM receiver. Not only for broadcast reception but also for amateur AM reception or as part of an AM transceiver.

Silicon Labs also makes Si4734/35 receivers; these need a CPU to control the receiver, but are of interest for amateur use because the frequency can be tuned in 1 KHz steps and the audio channel bandwidth in 7 steps. There is no need for the transmitter to be on the receiving channel…

Si4835 AM-FM receiver

Looking for a small SW broadcast receiver design, and pocket size, I came to the excellent range of modern DSP receivers in a single chip from Slicon Labs.

I made a test bed set up has been made for the Si4835 AM-FM receiver.

The target specification was:

  • minimal components,
  • no micro-controller,
  • low power,
  • backlash free mechanical tuning,
  • good sensitivity,
  • earphone,
  • robust housing,
  • a short and small antenna system for outdoor use,
  • and minimal controls.

The Si4835 makes miniature design possible on a PCB (see photo Figure 1).

The red Dip (band) switch was replaced by a rotary switch in the final receiver design (Figure 4).

The receiver power is minimal 2 x 1.2 = 2.4 volts or a one cell LI-ION accu.
5 volts is the maximum for the Si4835 chip; current consumption is 30 mA.

Fig 1. Testbed setup for the Si4835.

Fig 1. Testbed setup for the Si4835.

The receiver has an RF pre-amplifier transistor and the LF amplifier is the TDA7050T.
All receiver functions are in the chip; the schematic is very simple and can be built with minimal components (see schematic appnote AN555 Fig 2. below).

Only an LF amplifier has to be added to complete the receiver.

schematic

Fig 2. Receiver schematic Si4835 in the AN555 application note.

The Si4835 receiver has the following frequency bands–they are divided in sub bands 800 or 900 KHz wide (See Figure 3). The frequency step tuning is 10 kHz on AM, following the international broadcast raster standard.

Fig 3. Si4835 receiver sub bands.

Fig 3. Si4835 receiver sub bands.

This means there are 80 or 90 receive channels in the sub bands and make finding the BC stations on the scale more easy. The 10 KHz scale steps are linear. The frequency stability is locked to the 32 kHz X-tal via the synthesizer so there is no frequency drift. The AM LF audio channel is 5 kHz wide set by the DSP filter. Volume control can be done width 2 up-down push switches or by a LF potentiometer..

Fig 4. The experimental pocket aluminium receiver housing on PCB2.

Fig 4. The experimental pocket aluminium receiver housing on PCB2.

Receiving results

I have been testing many hours and I am surprised about this little receiver.

The receiving results are excellent on FM and AM and signals of 2 -3 uV are well received.

Also the audio quality is good–especially on FM. As can be seen in the frequency table the 40 and 20 meter band are in the range. Clear AM phone amateur transmission has been received when the transmitter was tuned on the 10 kHz raster in 40 meter band on AM.

Also AM modulated CW signals can be received bud not un-modulated carrier CW–they sound “plop…plop”.

The 5 kHz wide LF channel is a bid too wide so many CW signals pass through the audio at the time, but if AM modulated that should not be a serious problem.

The broadcast stations in the SW bands (when the daytime conditions are good) up to 20 MHz are good and strong.

Conclusions

The Si4835 receiver can be a fine broadcast receiver for outdoor work and if an AM transmitter is tuned in the 10 kHz raster this receiver can also used for amateur phone reception.

Addendum: The Si4734/35 is a better amateur AM Receiver

The Si4734 and Si4735 are a better receiver choice for amateur AM purpose because the frequency tuning can be done in 1 kHz steps. Also the BW of the LF channel can be adjusted to 1 kHz wide.

In Fig 5. from the programming APP note you see the code 0X3102 AM CHANNEL_FILTER it is possible to adjust the audio width by sending this code to the Si4734/35.

Fig 5. From the programming APP note

Fig 5. From the programming APP note

The LF bandwidth can be set on 1, 1.8, 2.5, 2, 3, 4 and 6 kHz wide.

This is excellent for modulated CW and AM phone discrimination in the audio channel.

The disadvantage is the need of an CPU and LCD display, “away from a minimalistic design”.

See also the note 1 and 2 improved 100 Hz rejection. See data sheet of the Si4734/35.

It look like that this receiver is a good receiver for building a modern AM-(AM)CW receiver or in a transceiver application. Tuning can be done digitally.

Think about this receiver [and the Si4835 chipset] when you intent to build a high tech AM – T/RX.

73 ‘ Joris van Scheindelen PE1KTH


What a fantastic home-brew receiver, Joris! I love the simple design of your receiver and the fact that it’s quite portable.  Thanks so much for sharing your notes and documentation.

Silicon Labs DSP chip homebrew receiver

DSP-HomebrewThe Silicon Labs Si4730 series DSP receiver chip powers many of the portable shortwave radios currently on the market.

Manufacturers are not the only ones implementing the chip in receiver design, however; radio enthusiasts are too.

I recently discovered this short video by a Japanese hobbyist who implemented the Si4734 in his receiver design:

While I don’t speak Japanese, the author also has a webpage of detailed design notes you might check out (click here to view). I used Google translate for a rough English translation of the page.

Have any readers made a homebrew receiver from a Silicon Labs DSP chip? If so, please comment!

Click here to download the Si4734 product information sheet.

SiLabs brings shortwave to car radios

Silicon Labs, a manufacture of DSP (Digital Signal Processing) chips that are in many of the shortwave radios we feature here on SWLing.com, is now taking their technology to car radios. They have announced the Si476x chip family which features AM/FM, longwave, shortwave (SW), NOAA weather band, FM RDS decoding and AM/FM HD Radio reception.

To my knowledge, this is the first time in years that shortwave has been strategically implemented in a car radio product.

Read their full press release below:

(Source: SiLabs Press release via Kim Elliott)

AUSTIN, Texas–(BUSINESS WIRE)–Silicon Laboratories Inc. (NASDAQ: SLAB), a leader in high-performance, analog-intensive, mixed-signal ICs, today introduced the industry’s most advanced automotive tuner IC family designed to deliver the highest RF performance coupled with advanced signal processing while reducing the cost and complexity of car radio systems. Offering superior price/performance for the global car radio market, the new Si476x tuner family provides a best-in-class multiband receiver solution for automotive infotainment head-units and AM/FM car radios from all classes of providers ranging from Tier 1 suppliers to aftermarket car radio makers.

According to J.D. Power and Associates, the global automotive market is expected to exceed 76 million light-vehicle unit shipments this year. The car radio technology deployed in these vehicles is evolving rapidly as innovations in communication technology proliferate in the automotive infotainment market. The basic car radio has been transformed into a sophisticated infotainment system that includes multiple tuners to deliver FM phase diversity reception, receive radio data system (RDS) data for info-navigation systems, support AM/FM HD Radio technology and provide detailed station quality metrics for living lists of broadcast content. These strenuous broadcast performance demands require advanced silicon innovations to enable a superior in-vehicle audio experience.

Silicon Labs developed the Si476x receiver family to address these major automotive industry trends. The Si476x receivers leverage Silicon Labs’ patented digital low-IF technology and combine most of the traditional external bill of materials into a highly integrated, single-chip CMOS solution. The receivers provide unprecedented flexibility, offering a modular architecture that supports scalable multi-tuner designs. The Si476x supports all worldwide broadcast radio bands including AM/FM, college FM, longwave (LW), shortwave (SW), NOAA weather band, unparalleled FM RDS decoding and AM/FM HD Radio reception. iBiquity Digital Corporation, the developer of HD Radio technology, has certified the Si476x family to provide AM/FM HD Radio tuner outputs and reception with compatible HD Radio demodulator ICs.

“The introduction of the Si476x tuner family represents a major new product offering from a world leader in RF products and a global player in the HD Radio market,” said Jeff Jury, chief operating officer of iBiquity. “Automakers are continuing to embrace HD Radio technology, with more than 20 automotive brands to date announcing the technology as a factory-installed infotainment feature. The Si476x family offers a compelling new solution for this market.”

The Si476x family represents the automotive industry’s first viable receiver alternative to enable developers to pair a best-in-class tuner IC with the optimal choice of audio digital signal processors (DSPs) to create highly cost-effective back-end audio processing designs. Silicon Labs has worked with leading silicon providers such as Cirrus Logic and Freescale Semiconductor to deliver comprehensive audio system solutions that break the expensive partitioning approach required by current car audio solutions.

“The combination of Cirrus Logic’s broad portfolio of audio ICs and Silicon Labs’ Si476x radio ICs provides automotive OEMs with a very powerful platform for building highly differentiated in-car entertainment products,” said Carl Alberty, director of marketing for audio products at Cirrus Logic. “By working closely with Silicon Labs, we have developed an optimized car radio platform that delivers best-in-class audio and RF technology, enabling our customers to build outstanding products.”

The superior linearity of the Si476x tuner’s integrated RF front-end, combined with a high-performance on-chip radio DSP and microcontroller, delivers outstanding RF dynamic range and immunity to multi-path fading. With this innovative architecture, the Si476x family raises the bar for such key features as selectivity, sensitivity, IMD3 break-in, desensitization, noise blanking, weak signal processing, dynamic channel bandwidth control and advanced dual-tuner FM phase diversity reception.

“The Si476x family not only delivers superior radio reception performance at the best system cost, it also provides unprecedented flexibility in audio processing solutions for car radio designs,” said Diwakar Vishakhadatta, general manager of Silicon Labs’ broadcast audio products. “With the introduction of the Si476x family, automotive developers are no longer locked into using more expensive bundled audio/radio solutions that may not address the audio processing requirements of their infotainment platforms.”

Pricing and Availability

Samples and production quantities of the Si476x car radio tuner ICs are available now in a compact 6 mm x 6 mm 40-pin QFN package. Pricing for automotive-grade Si476x tuner ICs begins at $11.62 (USD) in 10,000-unit quantities. The Si4763LNA-A-EVB and Si4767PD-A-EVB evaluation boards are available to automotive customers for $450 (USD).

The Si476x family, the latest addition to Silicon Labs’ portfolio of automotive-grade radio tuners, complements the company’s popular Si474x and Si475x tuner families, which target cost-sensitive entry- and mid-level radio designs. The Si476x family addresses premium-grade, performance-intensive automotive radio and head-unit requirements. For additional Si476x product information, please visit www.silabs.com/pr/automotive-tuner.

Silicon Laboratories Inc.

Silicon Laboratories is an industry leader in the innovation of high-performance, analog-intensive, mixed-signal ICs. Developed by a world-class engineering team with unsurpassed expertise in mixed-signal design, Silicon Labs’ diverse portfolio of patented semiconductor solutions offers customers significant advantages in performance, size and power consumption. For more information about Silicon Labs, please visit www.silabs.com.

Silicon Labs Si4734 DSP-based shortwave radios

The Silicon Labs Si4734/35

I have gone through our Shortwave Radio Index (SWRI) and tagged every portable radio that is based on the Silicon Labs Si4734 DSP chipset.

The Si4734 has been one of the biggest innovations to happen to portable receivers in recent years. When implemented well into a receiver design, the Si4734 can give a small portable exceptional selectivity and sensitivty through the power of DSP (Digital Signal Processing).

Simply click on this link to see a list of portable shortwave radios that are designed around the Silicon Labs Si4734:
http://swling.com/db/tag/si4734/

Silicon Labs ships one billionth DSP radio chip

Silicon Labs, the chip manufacturer behind some of the best portable shortwave radios in the market (including Tecsun and Grundig) has sold its one billionth DSP radio chip. Silicon Labs has been one of the best things to happen to the portable shortwave market this century. Their DSP chips lower the production cost of radios and enhance the performance with Digital Signal Processing.

I eagerly await the new Tecsun R-2010–an analog radio with the Silicon Labs’ Si483x DSP chip. Not only will it enhance the performance of this basic analog radio, but it should also decrease production costs by as much as 80%!

Here is the full SiLabs press release:

Industry’s First CMOS “Radio-on-a-Chip” ICs Widely Adopted in Leading Consumer Electronics and Automotive Designs

Reaching a major milestone in the broadcast audio market, Silicon Laboratories Inc [2]. (NASDAQ: SLAB), a leader in high-performance, analog-intensive, mixed-signal ICs, today announced that it has shipped its one billionth broadcast radio IC. Silicon Labs’ digital CMOS broadcast radios are widely used in handsets, portable media players (PMPs), personal navigation devices (PNDs), automotive infotainment systems, tabletop and bedside radios, portable radios, boom boxes and numerous other consumer electronics products.

Silicon Labs introduced the industry’s first single-chip FM receiver in 2005. As the industry’s smallest, highest performance and most integrated FM broadcast radio IC, the Si4700 [3] IC redefined how FM tuners were designed into consumer electronics products. At that time, traditional broadcast audio solutions were based on complex, costly analog architectures that required more than 30 discrete components. The highly integrated Si4700 revolutionized broadcast radio designs by offering exceptional, highly flexible performance, while simultaneously reducing component count by more than 90 percent and board space by more than 60 percent.

Over the past six years, Silicon Labs has rapidly expanded its broadcast audio portfolio [4] to more than 40 distinct products including FM radio receivers, FM radio transmitters/transceivers, AM/FM receivers, shortwave and weather band receivers, RDS data receivers and automotive radio receivers. These products are now the broadcast radio ICs of choice for many leading consumer electronics brands.

“Silicon Labs delivered the industry’s first monolithic all-CMOS FM receiver, providing breakthrough cost, size, integration and performance for broadcast receiver applications in handsets, navigation devices, media players and consumer electronics,” said Jag Bolaria, a senior analyst at The Linley Group. “The company has continued to drive market innovation in CMOS FM transmitters and multi-band AM/FM/SW and weather-band receivers, all widely adopted in the consumer electronics, portable and automotive markets.”

Silicon Labs’ broadcast radio ICs leverage the company’s patented low-IF digital architecture, which enables the highest level of selectivity and sensitivity performance for radios, resulting in reduced interference and superior reception. In addition, Silicon Labs broadcast receivers incorporate advanced audio processing technology that delivers sound quality that is unmatched by other competing radio receiver ICs.

“Silicon Labs thrives on pioneering new ways to solve difficult system design challenges with mixed-signal technology,” said Diwakar Vishakhadatta, general manager of Silicon Labs’ broadcast audio products. “Our single-chip FM, AM/FM receiver and transceiver families are a case in point. These products have helped our customers reduce the cost and complexity of their designs while enabling more features and functionality to help them differentiate their products in the marketplace. We continue to invest and innovate around our low-IF digital architecture to remain a strategic supplier of broadcast radio technology to the industry.”

Silicon Labs has approximately 100 issued and pending worldwide patent applications in audio technologies for its AM and FM related products.

For additional information about Silicon Labs’ broadcast audio products, please visit www.silabs.com/pr/broadcast.