User guide

MS-DMT Guide v1.04

Released 05-30-2014

HF SSB RADIO REQUIREMENTS

In general, an HF SSB transceiver with TXCO and 100w pep or greater output is required. A radio

capable of data transmission at 100% duty cycle is highly recommended for long broadcast

message transmissions.

NOTE: Additional fan cooling is recommended for extended transmitting such as sending greater than a

5Kb message at less than 600bps

The use of a dedicated Data Port for RX and TX audio provides the best audio characteristics as

well as consistent audio levels.

The STANAG 4203, “Technical standards for single channel HF radio equipment”, as excepted in

Appendix I herein, provides the detailed Military HF SSB radio requirements for the best

performance using MIL-STD data waveforms.

A 2.8kHz SSB filter centered on the PSK carrier which for MS110A is 1800Hz, is a must for best

results, less SSB filtering will result in poor results at high data rates above 600bps.

NOTE: The SSB filter must come as close as possible to meeting STANAG 4203 requirements. If not the

maximum data rate achievable will suffer. The design of the IF passband filtering determines how

faithfully it reproduces complex signals. MIL-STD serial tone signals contain information in both phase

state and amplitude value and occupy and instantaneous bandwidth as wide as 3kHz. The passband

response alters both phase and amplitude of a complex signal. Any marginal design considerations can

cause degraded performance of this complex waveform signals.

Any use of an Automatic ATU (AATU) must be made where the AATU has already been tuned to

the frequency and is not being tuned by the data transmission at the start when the preamble is

being sent, as such tuning will have a negative effect on the signal and thus the reception of the

preamble portion of the transmission used for sync. Retuning by the AATU during transmission

is also detrimental, as it will not only affect the data payload but also the known data used to

maintain sync. In addition, take into account the ATU wattage rating and its duty cycles rating.

For example the popular LDG tuners are rated in watts peak envelope power (PEP) and for ST

modes you need to use less than half its rating as the ST modem is a high duty cycle mode, its

nearly a continuous duty mode.