New 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.
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.
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