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.

P4dragon DR-7800

DR-7800, Technical Data:

Our 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.

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.

Special Features:

P4dragon DR-7400

DR-7400, Technical Data:

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.

The PTC-IIIusb allows direct connection to a USB interface of the modern notebook, and thus expands the SCS equipment program. The PTC-IIIusb is constructed using existing equipment technology and its application is to be found mainly in the connection of clients. As a speciality, the PTC-IIIusb is equipped with a transceiver control port, which allows remote control of the connected radio via software.

The Hardware

  1. Fully compatible to existing software by using a virtual COM port assigned by the USB driver.

  2. One single connector to the HF/VHF transceiver    for all modes.

  3. Transceiver control for ICOM, YAESU, SGC, KENWOOD and Rohde&Schwarz, including RS232 for modern transceivers.

  4. Supported by Airmail/GetFax.

  5. Special JVCOMM32-Mode for optimum cooperation with JVCOMM32.

  6. Packet-Radio with 300, R600, 1200, 9600 and 19200 baud with built-in DSP.

  7. With two high performance processors from Freescale, the PTC-IIIusb achieves outstanding flexibility.

  8. Sophisticated signal processing and analyzing maintains a stable HF link even during difficult  propagation conditions.

  9. Temperature compensated crystal oscillator.

  10. 2 MB of static RAM.

  11. Electronic (silicon) serial number.

  12. Noise free HF reception by use of HF suitable construction, 6 layer multilayer board and filtering of all inputs and outputs.

  13. Compact SMD assembly.

  14. Flash-ROM for easy firmware updates.

  15. Dimensions: 125 W x 43 H x 138 D mm, 1.69 H x 4.92 W x 5.43 D inches.

  16.  Weight: 450 g

  17. Power Supply:  +10 to +20 V DC, 300 mA max. Reverse polarity protected.

  18. Fuse self resetting.


  1. Max. 1200 Bit/s, incl. data compression.

  2. Automatic adaption to the channel quality in 4 speed levels.

  3. Bandwidth 500 Hz.

  4. Use of the most modern transfer mode technics: convolutional coding, Viterbi-decoder, soft-decision and Memory ARQ allows error free data transfers even with inaudible signals.

  5. Automatic frequency correction of ± 80 Hz.

  6. Automatic adaption of the radio’s transmit power to the channel quality is possible.


Like PACTOR-II, but:

  1. max. 5200 Bit/s, incl. data compression.

  2. Automatic adaption to the channel quality in 6 speed levels.

  3. Bandwidth 2400 Hz.

Robust HF-Packet

  1. Newly developed very robust modulation for HF-Packet-Radio and APRS.

  2. Max. 600 Bit/s.

  3. Automatic frequency correction of ± 250 Hz. APRS

  4. Fully automatic APRS-Beacon


The “Tracker/DSP TNC” has been designed by SCS for custom applications of transferring GPS positions and other small and reappearing sets of data from e.g. remote sensors by HF or VHF radio transmission using the new SCS "Robust-Packet" modulation. Typical applications are weather stations and the tracking of vessels, cars, trucks, containers and airplanes. The unit receives the GPS data from any external NMEA device and reports it to the host station.

Technical Data

  1. Universal TNC and APRS position tracker with DSP, USB-connection, output to control a switching relay (e.g. to switch the radio's power supply). NMEA input/output for GPS data, bi-coloured LED's, 4 DIP switch for the basic configuration.

  2. Optically isolated USB-connection to the computer, generally well filtered I/O's to avoid hum and susceptibility in HF environments. Metal case.

  3. Use of temperature stabilized oscillator (TCXO) for high reliablilty under all temperature conditions.

  4. 10..20 V DC supply power, use of highly efficient internal power regulators.

  5. Mini-Din connector, compatible to the usual transceiver "Packet-Connector".

  6. Currently implemented protocols: Generally AX.25, level 2.


  1. 300 baud AFSK (old HF-Packet standard) with new developed multi-detector: The DSP automatically processes a frequency range of +- 400 Hz looking for 300 bd transmissions and receives all detected signals in PARALLEL. No exact tuning by the user is necessary any more, but always perfect reception! Very important feature for automatically operating HF APRS gateways.

  2. 200/600 baud "HF Robust-Packet", 8-tone PSK, 500 Hz bandwidth, automatic frequency tracking (RX) +- 240 Hz.

  3. 1200 baud AFSK (standard Packet-Radio) with special filtering to avoid adjacent channel interference, and degradations by AC hum.

  4. 9600/19200 baud direct FSK (G3RUH compatible) with optimized DC removal by the DSP.


Position tracking mode to be activated by DIP-switch. Transmission of fixed or via NMEA (GPS) given position in free programmable time intervals in APRS format. Here the Tracker operates in "sleep mode" and just draws 15 mA of current (@ 13.8 V). Shortly before the next scheduled transmission it wakes up, switches on the radio, checks the channel for occupancies (DCD) and transmits the APRS datagram as soon as the channel is free. Afterwards the radio is switched off again and the Tracker enters "sleep mode".

  1. Operation modes and transmission level (audio) are adjustable by software command.

  2. Firmware upgrade via USB connector. Firmware stored in Flash-ROM, thus easily expandable for new operation modes with free of charge updates.

  3. Hostmode (compatible to all common hostmode programs like e.g. PAXON, WPP, etc.)

  4. KISS (compatible to all common KISS programs like e.g. UI-view).

  5. Small size, just 82 x 24 x 98 mm with 161 g of weight.

  6. Low power consumption (ca. 70 mA @ 13.8 V in regular operation and 15 mA in Tracker sleep mode).

Tracker / DSP TNC

DR-7800     DR-7400     PTC-IIIusb     Tracker / DSP TNC