The Bulgarian manufacturer ACOM has built a strong name in the amateur radio community primarily thanks to reliable tube designs, which for many years have formed and still form the robust background of many contest stations and top hamshacks. However, with the development of semiconductor technologies, the focus of development has shifted towards the so-called Solid-State solutions. One of the new additions to this product portfolio is the ACOM 1400S linear power amplifier, which covers all amateur radio bands from 1.8 to 54 MHz, including the WARC bands and the 6-meter segment.
Unlike older tube types that required manual tuning of the anode and antenna circuits using tuning capacitors, the ACOM 1400S delivers fully automated operation without the need for any fine-tuning when changing frequencies. This shift is crucial for modern styles of amateur radio operation, such as jumping from band to band when tracking DX clusters, reacting quickly to new spots in the RBN network, or operating in SO2R (Single Operator 2 Radios) and SO2V (Single Operator 2 VFO) modes. The amplifier can automatically track the frequency of the connected TCVR and switch the internal LPF (low-pass filter) circuits to the appropriate segment in a fraction of a second.
The fundamental technological innovation is the implementation of modern LDMOS (Laterally Diffused Metal Oxide Semiconductor) power transistors. Specifically, this is a robust type of transistor that is designed to withstand extreme PSV (standing wave ratio) values at the output and provide high signal linearity while maintaining excellent efficiency. The LDMOS transistors in this model work in combination with a sophisticated protection processor circuit that constantly monitors key operating parameters such as collector current, voltage, excitation power from the TCVR, heat sink temperature and reflected power from the antenna system. This constant hardware and software control pushes the reliability of the semiconductor output stage to a level that was previously only achievable with robust metal-ceramic tubes.
Another new feature is the integration of a full-color, high-resolution LCD display on the Remote Control Unit (RCU R06). This display element not only serves for the primary reading of peak output power and reflected power, but also offers a comprehensive text and graphic menu for diagnostics. The operator has an immediate overview of the amplifier status, transistor temperature and activation of individual protection circuits. All error messages and critical operating states are logged in the internal EEPROM memory, which simplifies any possible service diagnostics. In addition, the device architecture allows direct connection to external hamshack automation systems using CAT/AUX protocols.
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What are the advantages of the ACOM 1400S?
The main advantage of the ACOM 1400S amplifier is its instant-on capability. The user does not have to wait several minutes for the cathode of the tube to heat up, as is the case with classic designs. This factor is crucial when opening bands quickly, for example, when there is a sporadic E (Es) layer on the 6-meter band, when every second is decisive for establishing a rare QSO.
Kompaktné rozmery a relatívne nízka Weight v porovnaní s ekvivalentnými elektrónkovými modelmi s ťažkými transformátormi predurčujú tento model aj na náročnú portable prevádzku. Čoraz populárnejšie expedičné aktivity v rámci programov IOTA (Islands on the Air), POTA (Parks on the Air) alebo víkendové kontestové expedície z prechodných QTH vyžadujú techniku, ktorú je možné jednoducho prepravovať and rýchlo uviesť do prevádzky. Vďaka spínanému napájaciemu zdroju, ktorý je integrovaný priamo v tele zosilňovača, odpadá nutnosť prenášať externé napájacie bloky.
Excellent linearity and low intermodulation distortion (IMD) are among the strongest features of this device. The LDMOS output stage produces a clean signal without unwanted harmonics and parasitic emissions that would cause interference to nearby amateur radio stations or household appliances. The signal purity is verified by rigorous tests, thanks to which the device meets the international IARU standards and national telecommunications regulations for the suppression of unwanted broadcast products with a margin. This ensures that even at full power the signal remains narrow in the band and does not overload the input circuits of other operators' receivers.
Operational advantages include an extremely quiet and efficient cooling system. Electronically controlled fans dynamically change their air flow rate depending on the actual temperature of the LDMOS transistor. When receiving or during periods of lower load, the amplifier is practically inaudible, which contributes to the acoustic comfort of the operator in the Shack. During prolonged contest loads in high duty cycle modes such as RTTY, FT8, FT4 or CW pile-up, the cooling system smoothly adjusts to maximum power to reliably maintain the temperature of the semiconductor junction within safe limits.
Flexibility in connectivity allows the amplifier to work seamlessly with almost any commercially available transceiver. Icom (CI-V), Yaesu (CAT), Kenwood, Elecraft protocols are supported, as well as modern FlexRadio networks. In case the TCVR does not have a data link for frequency transmission, the ACOM 1400S uses a built-in digital frequency counter. It analyzes the RF signal at the input during the first milliseconds of transmission and automatically selects the correct band. Protection against exceeding the maximum excitation power prevents damage to the input if the operator accidentally forgets to reduce the power on the radio.
Technical specifications ACOM 1400S
The technical parameters of the ACOM 1400S amplifier represent the top of the class of solid-state linear medium-power amplifiers. The table below specifies in detail the electrical, mechanical and operational parameters of the device based on the official manufacturer's documentation.
| Parameters | Value and technical specifications |
|---|---|
| Frequency range | All amateur radio bands from 1.8 MHz to 54 MHz (including WARC segments) |
| Rated output power | 1200 W (±0.5 dB) stable peak RF power (PEP or continuous carrier) |
| Drive Power | Typically 40W to 60W to achieve full output power |
| Input impedance | 50 Ohm nominal, unbalanced, PSV typically below 1.2:1 across the entire range |
| Harmonic suppression | Better than 60 dB on HF bands, better than 65 dB on 50 MHz band |
| Intermodulation distortion (IMD3) | Better than 30 dB below the two-tone peak-to-peak (PEP) level at rated power |
| Supply voltage | Switch mode power supply (SMPS) with a range of 100 V to 240 V AC, frequency 50/60 Hz |
| Maximum network consumption | Approximately 3000 VA at full power and 230 V AC supply |
| Active element used | The latest generation of highly durable LDMOS transistor |
| Cooling | Forced air cooling with continuously adjustable fan speed |
| Dimensions (W x H x D) | 327mm x 155mm x 413mm |
| Weight | Approximately 14.5 kg |
The device has full hardware protection against overvoltage in the power supply network, overcurrent in the output stage, excessive excitation at the input and exceeding the safe operating temperature. Built-in ALC (Automatic Level Control) circuits protect the TCVR driver from output overload and help maintain a constant modulation level. Receiving and transmitting switching (T/R switching) is implemented using fast vacuum or semiconductor relays with low latency, which allows full operation in QSK mode (full telegraph break-in) without the risk of PTT line delay.
Video from Youtube
For a more detailed look at the design, architecture of the internal circuits, and real testing of the amplifier stage in real hamshack operating conditions, we recommend watching the following video demonstration:
Price and where to buy
ACOM 1400S is a premium product falling into the category of highly reliable amateur radio equipment, which is reflected in its final market price. Prices on the European market are stable, but slight variations depend on current exchange rates and the conditions of specific distributors. In general, the final price for European amateur radio operators ranges from 3,300 EUR to 3,600 EUR including VAT.
The device can be purchased from several established European dealers of amateur radio equipment. For Slovak and Czech operators, availability is ensured through official distribution channels, which guarantee not only the delivery of the device, but also full warranty and post-warranty service. The main verified dealers where the ACOM 1400S is available for a long time or on order include the following companies:
- Wimo (Germany): One of the largest European distributors of amateur radio equipment, yagi and quad antenna systems and accessories. Offers stable stock availability, reliable logistics and direct shipment of packages to Slovakia with full technical support.
- DX Engineering (USA): Global retailer of equipment for demanding amateurs. Buying from this store is an alternative, especially for radio amateurs outside the European Union, or when taking advantage of special stock promotions, while taking into account the additional costs of import duties and ocean shipping.
- Radioamater.cz (Czech Republic): A regional retailer that provides radio amateurs in the Czech Republic and Slovakia with maximum comfort in terms of communication and speed of delivery. The advantage is direct communication in the native language and a simplified process for any warranty claims.
When purchasing a device, it is strongly recommended to check the firmware version and the availability of connection cables for the specific type of your TCVR. Most retailers offer original ACOM data cables for individual radio brands as optional accessories, which greatly simplifies the initial integration of the power stage into the structure of your home or contest hamshack.