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Digital Modes

Military Support Network Stations*

In order to facilitate MSN station check-in's during periods when voice communications are hard to hear, in addition to voice calls, we will make net calls in a digital mode. There are many modes available, but until further notice we will use the following for MSN station check-in and roll call radio check...

Digital Mode Settings: Olivia (amateur radio digital mode)
32 tones
1,000 Hz bandwidth
Audio centered on 1,500 Hz (Space = 1,000 Hz and Mark = 2,000 Hz)
The question has been asked: Why is the MSN using the Olivia mode instead of M110A, MT-63, MFSK, or other digital modes?
Answer: When M110A, MT-63 and MFSK, as well as most other digital modes and voice have faded and can't be copied due to propagation, the Olivia mode works very well under these weak signal conditions and is still printing. Olivia is a digital mode designed to work in difficult (low s/n ratios plus multipath propagation) conditions on HF bands. The signal can be decoded even when it is 10-14 db below the noise floor (i.e. when the amplitude of the noise is slightly over 3 times that of the signal). It can also decode well under other noise, QSB, QRM, flutter caused by polar path propagation and even auroral conditions. Many different modes were tested, evaluated and rejected. Olivia-32 is a slower error correcting mode and it works very well, which is why it was selected.

If stations hear each other well enough on voice, any digital mode may be used to pass traffic.

Digital Program: There are many digital mode programs available, but the network manager recommends the Fast and Light DIGItal modem program Fldigi for standardization. It's free and works on most of the amateur radio digital modes, including those used on MARS. However, it doesn't work on the MIL-STD 110A mode, which is not authorized on the American amateur bands.

If your digital program has it, it is recommended the TxID and RxID be turned ON while using MSN frequencies. This allows tracking and mode changes automatically while receiving. However, be aware that your actual center frequency depends on your program/sound card being properly calibrated with WWV and using the Tx and Rx ID will move your center audio frequency if the transmitting station you are receiving is off-frequency, or change your mode if a different one is being received.

Military, SHARES and Authorized Government Stations*

If you are able to use the Olivia mode specified above, please feel free to use it. If you request communication using digital modes, you will be asked which mode you want to use if you didn't specify the mode. If the MSN station is operational on that mode, it will be used. If the MSN station doesn't have it, the operator will advise which digital mode/s they can operate.

Not all of the MSN stations are 100% operational on the MIL-STD 110A mode yet and those that are, are using soundcard software. At the NCS discretion, if operational on M110A, they will make a net call, or have another station make an M110A net call using the following settings...

Digital Mode Settings: MIL-STD 110A
300 BPS Long
1,800 Hz PSK Carrier
Important Note: 1. MIL-STD 110A is NOT a weak signal mode. When SYNC is lost (happens quite often), nothing will print and the traffic is lost.
2. The following excerpt is copied from the MSDMT User Guide - "The 110A ST waveform and other MIL-STD/STANAG waveforms perform best with an HF SSB 100w or greater (where 400w plus for CONUS broadcasting is recommended . . .)"
3. When using M110A, make sure your transmit and receive filters are open to 2.8 KHz.

Other Digital modes

There are many Amateur Radio digital modes available for use and in addition, there are variations within most digital modes such as the number of tones, bandwidth, baud rate, long or short inter-leave, inverted and others. If stations are trying to communicate using a digital mode and are not set to the exact same parameters, they will never be able to communicate with each other. Make sure to discuss the mode settings before attempting to use any digital mode.

*Whenever possible, digital net calls shall be made. It is at the discretion of the NCS to make the digital net calls, have the ANCS, or another station make digital calls. This applies to both the Olivia-32 and MIL-STD 110A digital modes.

This page updated 26 December 2018 @ 1912 Zulu

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