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SCS P4dragon DR-7400
High Performance HF-Radio Modem

The compact HF modem P4dragon DR-7400 offers a lower-priced entry to the P4dragon modem class. The DR-7400 has been optimzed for use with the new high-end data transmission mode PACTOR-4. This allows unparalleled fast and robust data links via shortwave. Email almost like at home - from any point on earth. The DR-7400 ist software compatible to the PTC-II series and to the DR-7800 so that existing PACTOR software (Airmail, RMS Express, Alpha etc) can continued to be used. The elegant design as well as the easy upgrade possibilities (free updates!) complete the concept of the “Little Dragon“. Of course, the DR-7400 also provides TRX remote control, a GPS input and an (optional) Bluetooth interface.

  • Switch plugs and go… Due to the plug compatibility of the radio ports, a change from the commonly used PTC-II technology to the innovative P4dragon technology is very easy. Change over the plugs, turn on, and enjoy PACTOR-4!
  • To the limit. DR-7400 means “High end” in both hardware and software. 6.4 Billion arithmetical operations per second, and hand optimized DSP algorithms, enable an unparalleled PACTOR performance. – Reference class!
  • P4dragon. The Ouroboros logo is not only a symbol for globe encircling HF-communications. It also symbolizes the many iterative operations, without which PACTOR-4 could not approach so close to the Shannon boundary.
  • PACTOR-4. Max net speed 10500 bps. 1.5 - 3 x faster than P3. Backwards compatible. 2400 Hz bandwidth. Highly adaptive. Highly resistant to interference. 6 auto notches. Adaptive equalizer.

Pactor 4

  • Data throughput: Maximum 5512 bps without compression. Approx 10500 bps with PMC using text. This is reached with approx +16 dB @ 4 kHz in an AWGN channel. Under the usual channel conditions 1.5 – 3 times faster than PACTOR-3
  • Compatibility: Backward compatible to PACTOR-1/-2/-3. Automatic negotiation during link setup. Noticeably improved reception with PACTOR-2 and PACTOR-3
  • ARQ protocol: Synchronized, similar to PACTOR-3, except 10 instead of 6 speed levels (“Waveforms”) and faster switching. Bandwidth always smaller than 2400 Hz.
  • Channel equalization: Iterative adaptive equalizer for the coherent speed levels (5 – 10), RAKE receiver with maximum ratio combination for the splayed speed levels (2-4). Real-time multitasking operating system.

Special Features:

P4dragon modems use a very complex newly developed synchronization algorithm for the link initialization (both ”normal” and ”robust”). This allows that on receipt of a ”connect” request from a calling station, an immediate and loss free automatic frequency compensation of up to ±280 Hz! can be applied to the receiver. The receiver of the ”Connect request” e.g. the Winlink-RMS or similar base station corrects its own receiver frequency AND the transmit frequency of the short radiated acknowledgement directly after the FSK synchronization. The modem of the calling station must then only correct the small remaining error (max ±10 Hz) after the link initialization. Thus PACTOR-2 /-3/-4 connects start immediately with full speed, independent of the initial frequency error. Base stations which operate using DR-7X00 modems thus also allow users initiating a link with a frequency error of greater than 30 Hz immediate full speed operation, even when the user only uses a PTC-II. (PTC-II modems in contrast only have a capture range of ±100 Hz for the reception of a link request, and automatically reduce the PACTOR-3 throughput when frequency errors of greater than ±30 Hz are measured.)

A high Tolerance to frequency errors is especially useful on the ”higher” shortwave bands. A relatively ”normal” frequency error of only 10 ppm produces a frequency error on the 20 meter band for example of 140 Hz.

DR-7400 Technical Data
Operating Modes
PACTOR-4, PACTOR-3, PACTOR-2, PACTOR-1, Weather-Fax (receive), GPS Decoder
Quad core DSP by Freescale
Computing Power
6400 MIPS
Permanent Storage
Flash-ROM (update via the user interface), EEPROM for paramaters
Operating System
Real-time multitasking operating system

User Interfaces:
USB, Bluetooth (in DR-7403)
GPS Input (RS232 and TTL)
Input impedence: 47 kOhm
Output impedence: 1 kOhm
Output level (open output): 3V p-p max; freely adjustable
Input level: max 3V p-p
Mic input (high impedence)
Speaker output (low impedence, 2 W)

8 dual-color LED's (green, red) indicating all important operating states and signal tuning
Time Base
Temperature stabilized (TCXO, 1 ppm)
Transceiver Control
Over and internal multi-level interface, compatible with Kenwood, Icom and Yaesu transceivers and many other models
Control Elements
Sensor key for ON/OFF, rear-side 4x DIP switches for basic configuration
Power Consumption
400 mA (max. with 10V input voltage)
Power Input
max. ~3W at 13.8V
125 x 43 x 138 mm (w x h x d)

with Bluetooth. Scroll down for non-Bluetooth version.


scs dr-7400

Package includes:
• P4dragon DR-7400 High Performance HF-Radio Modem
• Installation Guide
• 8 pole DIN cable
• 13 pole DIN cable
• USB cable
• RJ45 Patch cable


pdf DR-7400 Data Sheet
pdf DR-7X00 Installation Manual
Software & Firmware Downloads


scs dr-7400

scs dr-7400
Rear view


SCS P4dragon DR-7400

SCS P4dragon DR-7403 with Bluetooth

scs 8070
SCS-8070 Pactor Modem Remote Control Cable
SCS Pactor Modem Transceiver Remote Control Cable 13-pin DIN with open end cable.

scs 8080
SCS-8080 Transceiver Remote Control Cable RS232 for TS-450/480
This cable is used to connect the Pactor Modem to the RS-232 (Female) remote control of your transceiver.

scs 8160
SCS-8160 Audio Connection Cable for KENWOOD 13-pin DIN
Connect your PTC-II series PACTOR modem to all KENWOOD Transceiver with the ACC 13-pin DIN plug. For TS2000/440/450/570/850/870.

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