The ATS20 SI4732 radio receiverhas emerged as a surprisingly capable compact multi-band radio that punches well above its weight class. This diminutive device, based on Silicon Labs’ SI4732 chip architecture, represents a fascinating convergence of modern digital signal processing technology and traditional radio reception capabilities.
After extensive testing and user feedback analysis, this comprehensive review examines whether the ATS-20 lives up to its growing reputation in the shortwave listening community.
ATS20 radio First Impressions and Build Quality
The ATS20 radio immediately impresses with its compact form factor and solid construction. The metal case and crisp display surprised reviewers, along with the inclusion of RDS functionality. The radio measures approximately the size of a smartphone but with considerably more thickness, making it genuinely portable while maintaining a substantial feel that inspires confidence in its durability.
The aluminum alloy construction provides excellent electromagnetic shielding while keeping the weight manageable for portable operations. The rubber feet on the bottom prevent sliding during desktop use, and the overall build quality suggests this radio can withstand the rigors of travel and outdoor use.
The telescopic antenna extends to a reasonable length for such a compact device, though serious users will want to consider external antenna options for optimal performance.
The front panel features a small but surprisingly clear LCD display, approximately “the size of a postage stamp” as one reviewer noted. But with crisp visibility that provides all essential information including frequency, mode, bandwidth, volume, and signal strength indication. The control interface consists of several small buttons with “+” designators and a plastic tuning encoder that, while not luxurious, proves functional and reliable in practice.
Technical Specifications and Features
The ATS20 radio covers an impressive frequency range for such a compact device. The radio receives:
- FM: 64-108 MHz (with RDS support)
- Medium Wave (AM): 522-1710 kHz
- Long Wave: 153-279 kHz
- Short Wave: Multiple bands covering 2.3-21.85 MHz
- SSB capability on both USB and LSB modes
The radio operates on 5V DC power, drawing approximately 1 ampere during operation. The built-in lithium-ion battery provides several hours of operation, though some users report the standard 500mAh battery capacity is limited and have successfully upgraded to 2700mAh units for extended operation.
The SI4732 chip architecture provides seven selectable bandwidth options: 1.0, 1.8, 2.0, 2.5, 3.0, 4.0, and 6.0 kHz, allowing users to optimize reception based on conditions and interference levels.
The digital signal processing capabilities of the chip contribute significantly to the radio’s performance, providing noise reduction and signal enhancement that would have been impossible in analog radios of similar size and cost.
ATS20 Performance Analysis
FM Reception
FM performance proves excellent for a radio of this size and price point. The audio quality from the top-mounted speaker surprised reviewers, delivering clear, distortion-free sound suitable for music listening.
The RDS functionality works reliably, displaying station information when available. The included telescopic antenna provides adequate FM reception in most environments, though the radio benefits from the antenna switching feature that optimizes performance for different frequency ranges.
Medium Wave and Long Wave
AM reception capability varies significantly with location and antenna configuration. Using just the telescopic aerial, acceptable LW and MW reception can be achieved during daytime hours, depending on location.
The radio demonstrates good sensitivity to medium wave stations, making it suitable for local and regional AM broadcasting reception. Long wave performance, while functional, benefits greatly from external antenna connections for optimal results.
Short Wave Performance
Short wave reception represents the ATS20’s primary strength and the reason most users purchase this radio. At night, users report successful reception of major international broadcasters including China Radio International, Radio Romania International, and Voice of Greece, plus smaller stations.
The radio handles both broadcast and utility stations effectively, with users successfully monitoring HF VOLMET aviation weather services and amateur radio communications. The SSB performance deserves particular attention. Users report successful listening to radio amateurs on SSB, HF VOLMET, CW, and RTTY signals, though the radio is not positioned as a DX (long-distance) machine. On shortwave ham bands, the radio works fairly well on SSB, making it suitable for casual amateur radio monitoring.
However, the SSB performance benefits significantly from firmware updates. The original software was described as “clunky” on SSB, but later firmware versions provide much better features, including BFO adjustment capabilities that allow proper calibration of SSB frequencies. This calibration feature addresses frequency accuracy issues that can make SSB signals sound distorted or off-frequency.
ATS20 radio – Firmware and Software Considerations
The ATS20 radio ships with firmware version 3.0.7b developed by PU2CLR, but the radio’s true potential emerges with firmware updates. The Arduino-based architecture allows for significant software improvements, and several developers have created enhanced firmware versions that dramatically improve usability and performance.
Key firmware improvements include:
- Enhanced SSB performance with better frequency stability
- Improved user interface with more intuitive control schemes
- BFO adjustment capabilities for accurate SSB tuning
- Enhanced signal metering and display options
- Better power management and battery monitoring
Users report that updated firmware makes the radio “much more ergonomic and usable,” with the BFO adjustment allowing proper calibration so SSB signals sound correct when dialed to the correct frequency.
This upgrade capability represents a significant advantage over traditional analog radios, allowing the ATS-20 to improve over time rather than becoming obsolete.
ATS20 radio – Antenna Considerations and External Connections
While the ATS-20 includes a functional telescopic antenna, serious shortwave listening requires external antenna connections. The radio includes an antenna input jack and switching system that optimises reception for different frequency ranges.
Users report that connecting to better antennas, such as active antennas or wire antennas, significantly improves reception, enabling RTTY and fax reception capabilities.
The antenna switching feature requires user attention when changing bands – the switch position must be changed for optimal VHF FM versus HF/MF/LF reception. This manual switching, while requiring attention, provides optimal impedance matching and performance across the radio’s wide frequency range.
For portable operation, the telescopic antenna proves adequate for strong local signals and major international broadcasters during favourable propagation conditions. However, the radio’s potential shines when connected to dedicated HF antennas, random wire antennas, or active antenna systems.
ATS20 User Experience and Practical Considerations
The ATS20 radio presents a learning curve for users unfamiliar with software-defined radio concepts or modern compact receiver interfaces. The small display and button layout require good lighting and possibly reading glasses for comfortable extended use. However, the two-page instruction leaflet is well-written and not in “Chinglish,” making the device intuitive to operate. Battery life presents the primary limitation for extended portable use.
The standard 500mAh battery “soon runs out,” leading users to upgrade to larger capacity units or rely on power bank charging during extended operations. The USB charging system provides convenient power options, accepting standard 5V USB power from power banks, computer USB ports, or wall adaptors.
The radio performs well in various environments, though it “picks up all the noisy laptops inside the house”, indicating sensitivity to local electronic interference that requires consideration in placement and use. This sensitivity, while sometimes problematic, also contributes to the radio’s ability to receive weak signals when properly positioned.
ATS20 radio Comparison with Contemporary Radios
One experienced user noted that the ATS-20+ is “FAR better than my first Realistic DX302 which back in the day cost about £300,” acknowledging that this comparison accounts for inflation and technological advancement. This perspective highlights the remarkable value proposition the ATS-20 represents in the current market.
When compared to other compact shortwave receivers in its price range, the ATS-20 stands out for its firmware upgrade capability, solid construction, and comprehensive frequency coverage. While it may not match the sensitivity and selectivity of communications receivers costing several times more. It provides exceptional value for casual listening, travel use, and entry-level shortwave exploration.
ATS-20 Limitations and Considerations
Several limitations deserve mention in any honest assessment:
- Battery Life: The standard battery capacity limits extended portable operation
- Display Size: The small screen challenges users with vision limitations
- Frequency Stability: Some frequency drift occurs as battery voltage drops
- Interference Sensitivity: The radio can be affected by local electronic noise
- SSB Performance: Optimal SSB operation requires firmware updates and careful calibration
Conclusion and Recommendations
The ATS-20 SI4732 radio receiver represents remarkable value in the compact shortwave receiver market. Its combination of solid construction, comprehensive frequency coverage, and upgrade potential makes it an excellent choice for DXers:
Ideal for:
- Travel and portable shortwave listening
- Entry-level shortwave enthusiasts
- Users wanting a compact backup receiver
- Those interested in exploring software-defined radio concepts
- Casual monitoring of amateur radio and utility stations
Less suitable for:
- Serious DX listening requiring maximum sensitivity
- Users preferring traditional analog controls
- Those needing extended battery operation without charging
- Applications requiring laboratory-grade frequency accuracy
As one satisfied user summarised: “Everything about it is what was promised, and I have been well pleased”. The ATS-20 delivers on its promises while providing upgrade potential that keeps it relevant as user needs evolve. For its price point, the ATS-20 represents one of the best values available in portable shortwave receivers. Also, it won’t replace a high-end communications receiver for serious applications. It provides an excellent introduction to shortwave listening and serves admirably as a compact travel companion for radio enthusiasts.
The ability to upgrade firmware and the active development community ensure this radio will continue improving. It is a wise investment for anyone seeking portable shortwave capability without a substantial financial commitment.
The ATS-20 proves that in the modern era, sophisticated radio reception capability can be packaged in remarkably compact and affordable devices. For those willing to invest a small amount of time in firmware updates and antenna optimization, the ATS-20 provides years of reliable shortwave listening enjoyment.
ATS_EX Firmware
This is advanced firmware for ATS20 that is working on Arduino Nano and Si473x DSP receiver chip. ATS_EX is created by Goshante, based on PU2CLR firmware and inspired by swling.ru firmware with closed source.
Latest version: v1.18 (03.04.2024)
| ATS EX Firmware for ATS-20 DSP Receiver | Starter pack for ATS20 Users |
| ATS20 Facebook group |
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I really like mine but if seems to suffer from poor AGC symptoms on strong CW (too slow with pumping)