Photo by SCS Co.

New P4dragon DR-7800, a completely new development, and the first PACTOR-4 capable short-wave modem. P4dragon stands for the most ingenious data transfer algorithms and the highest computing power possible in PACTOR controllers of the 4th generation.

The fast quad-core DSP used in the DR-7800 enables for the very first time, a high data rate, approaching very close to the Shannon limit, as well as an extremely high immunity to interference. PACTOR-4, with its 10 speed levels and adaptive equalizer, adjusts itself ideally to varying channel conditions, and guarantees reliable data transfer even under very poor propagation conditions. Due to this high reliability, P4dragon modems allow transmission of safety relevant data via shortwave, and provide an excellent value for money when compared to many satellite services.

New 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.

  • 10500 bps net
  • 2x faster than P3
  • Backward compatibel
  • 2400 Hz bandwidth
  • Highly adaptive
  • 10 Speedlevels
  • High interference immunity
  • Auto-notches
  • Adaptive equalizer


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-7800 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.

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