WPA NBEMS/FLDIGI
EmComm Modes

The WPA NBEMS group will be focusing on 3 primary digital emergency communications modes:

MT63 - Olivia - DominoEX

Each mode has it's advantages and disadvantages and our recommendations are based on extensive field testing under varying situations and conditions.

MT63 2k Long - Local FM Comms

For local portable, mobile and fixed station operations on 2m and 70cm FM (repeater or simplex), MT63 2K long is our primary mode for detailed situation reports and database transmission and has been chosen for the following reasons:

- Can be used very effectively without a sound card interface (audio coupling)
- Extremely effective under poor RF conditions
- Extremely accurate decoding (major duplication of data and forward error corrected)
- Very forgiving on sound card tuning and calibration when used on FM
- Excellent for sending larger situation reports or databases

MT63 1k Long - Regional/Local HF Comms

For regional and local portable, mobile and fixed station operations on HF USB under moderate to good condition, MT63 1K long is our primary mode for detailed situation reports and database transmissions and has been chosen for the following reasons:

- Very effective under moderate to good RF conditions
- Extremely accurate decoding (major duplication of data and forward error corrected)
- Works extremely well under QRM and QRN conditions - Excellent for sending larger situation reports or databases

Disadvantages:

- Requires fairly accurate tuning
- Does not work well under very poor RF weak signal conditions
- Long decoding FEC delay not well suited for short keyboard to keyboard communications
- 1k audio bandwidth is very wide as compared to other digital modes

Olivia 16 Tone/500 Hz - Regional/Local HF Comms

For regional and local portable, mobile and fixed station operations on HF USB under good to poor conditions, Olivia 16/500 is our primary mode for short messages and situation reports and has been chosen for the following reasons:

- EXTREMELY accurate decode, even under the worst conditions (major duplication of data and forward error corrected)
- Very resiliant to QRM and QRN
- Best suited for short messages and situation reports under poor HF conditions

Disadvantages:

- Slow data rate (slightly faster than writing speed)
- 500 Hz audio bandwidth is wider than several other modes

DominoEX11(FEC) - Regional/Local HF Comms

For regional and local portable, mobile and fixed station operations on HF USB under good to moderate conditions, DominoEX11(FEC) is our primary mode for short messages and keyboard to keyboard communications and has been chosen for the following reasons:

- Duplication of data and forward error correction provides good copy under moderate RF conditions
- Well suited for keyboard to keyboard (chat)
- Relatively narrow audio bandwidth (approx. 200 Hz)
- More forgiving on tuning inacuracies than Olivia
- Resiliant to QRM and QRN

Disadvantages:

- Not available on many programs other than NBEMS/FLDIGI and Multipsk
- Not as reliable as Olivia 16/500 under very weak RF conditions

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