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SCS P4dragon DR-7800
High Performance HF-Radio Modem

The HF modem P4dragon DR-7800 is the uncompromising advancement of the legendary PTC-II which is designed for professional deployment and for the ambitious amateur radio operator. DR-7800 is software-compatible with PTC-II which means that one may continue to use the existing software, such as AirMail, RMS Express, Alpha, etc., for PACTOR as well. Due to the pin compatibility of the radio equipment ports a change-over from the well-tried PTC-II technology to the innovative P4dragon technology is made convenient: re-plug, switch on and enjoy the higher speed and robustness with the PACTOR connectivity!

The elegant design and the excellently readable and informative OLED display including the simple upgrade facility (updates free of charge!) round off the concept of the absolutely latest shortwave modem from the house of SCS.

DR-7800 can be ideally used for HF email, for example, over the Winlink network. Externally, it stands out due to its high-resolution OLED display which, among other things, can be configured for waterfall and spectral views. Thanks to its reliability and low power consumption of 3 W, the new modem is also well-suited for distress radio communications and other applications under severe conditions.

  • 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-7800 means “High end” in both hard and software. 6.4 Billion arithmetical operations per second, and hand optimized DSP algorithms, enable an unexcelled 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. 2x 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: Strictly 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-7800 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-7803)
GPS Input (RS232 and TTL)
2x transceiver ports ("Main" and "Aux", switchable, optional for dual-port operation), symmetrical and asymmetrical operation PTC-II compatible connectors,
Input impedence: 15 kOhm
Output impedence: 300 Ohm
Output level (open output): 9V p-p max; freely adjustable
Mic input (high impedence)
Speaker output (low impedence, 2 W)

64x256 pixel, OLED, blue, high contrast, excellent readability, with no viewing angle problems, brightness adjustable in 16 steps, display of waterfall and spectral views and much more, display modes can be adjusted
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 and menu control via the OLED display, rear-side 4x DIP switches for basic configuration
Power Consumption
400 mA (max. with 10V input voltage)
Power Input
max. ~3W at 13.8V
172 x 43 x 205 mm (w x h x d)

with Bluetooth. Scroll down for non-Bluetooth version.


p4dragon dr-7800

Package includes:
• P4dragon DR-7800 High Performance HF-Radio Modem
• Installation Guide
• 8 pole DIN cable
• 13 pole DIN cable
• USB cable
• RJ45 Patch cable


pdf DR-7800 Data Sheet
pdf DR-7X00 Installation Manual
Software & Firmware Downloads


scs p4dragon 7800
Waterfall Display

scs p4dragon 7800
Rear with plugs

scs p4dragon 7800
Front opened

scs p4dragon 7800
DR-7803 board
with Bluetooth installed

SCS P4dragon DR-7800

SCS P4dragon DR-7803 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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