MD-674

MD-674

Frequencies	3 MHz,30 MHz
Frequency Range	3 MHz - 30 MHz
Mode	USB
Modulation	FSK
ACF	—
Emission Designator	—
Bandwidth	200 Hz,250 Hz,300 Hz
Location	United States
Short Description	MD-674, also known as Wireline FSK, is a very old United States Military FSK Modem from the 1960's. Uses 85 Hz FSK shift. Speeds of 50 Bd, 75 Bd, 100 Bd, and 150 Bd have been logged. No longer seen today.
I/Q Raw Recording	—
Audio Sample

MD-674, also known as Wireline FSKFrequency-Shift Keying, is a very old United States Military FSKFrequency-Shift Keying Modem from the 1960's. Uses 85 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). FSKFrequency-Shift Keying shift. Speeds of 50 BdBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second., 75 BdBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second., 100 BdBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second., and 150 BdBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second. have been logged. No longer seen today.

The MD-674 Modem is designed to output to a 4-channel VFTVoice Frequency Telegraphy wire circuit, so it's use is not in wireless transmission but wired transmissions over telephone circuits. The MD-522 is the wireless version of this signal, designed for transmitting with a radio frequency transmitter and receiver.

Sample

The given sample is 100 BdBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second. and 85 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). shift.

Decoding Software

Professional Equipment/Software

• go2DECODE
• go2MONITOR
• Wavecom W-Code
• Wavecom W-Spectra

Additional Links

• WAVECOM Database: HNG-FEC
• shoc Database: MD-674
• Operators Manual for MD-674, Low-Speed Wire Line Modem. US Army Technical Manual TM 11-5805-424-15. June 1967