ALLISS

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ALLISS is a somewhat rotatable antenna system for high power shortwave radio broadcasting in the 6 MHz to 26 MHz range. An ALLISS module is a self contained shortwave relay station that is used for international broadcasting.

ALLISS is a special design case of HRS type antennas. True ALLISS systems have solid radiators (horizontal radiating elements) versus tensioned flexible (open) radiators found with all other variations of ITU HRS type antennas systems. The name is based on a concatenation of two French towns ALLouis and ISSoudun.

There are some factors that separate true ALLISS technology from 'run of the mill' rotatable HRS Type antennas. Thales pseudo ALLISS rotatable antenna designs were procured from other antenna manufacturers that Thales acquired by corporate transactions. Technically only solid radiators distinguish true ALLISS systems from all other rotatable HRS type antennas. Only about 12% (estimate) of all HRS antennas in use globally are rotatable, and of these only 28 of the ALLISS systems have solid radiators. One must assume that only about 10% of HRS type antennas are rotatable, but compiled statistics are fragmentary. Only about 20% of rotatable HRS antennas are ALLISS, but this may be a slight overestimate. The Transmitter Documentation Project has most but not all stats on shortwave relay station antennas in use or historical. The Chinese SARFT is said to contain replicated ALLISS module technology, so to consider ALLISS technology as being exclusively in the domain of Thales is no longer true.

Information about ALLISS can also be found associated with Ampegon, Thales Group, Thomson CSF.

ALLISS technology, due to its cost and complexity—is out of reach to most consumers as a consumer product. Cheaper solutions to ALLISS exist in the shortwave broadcasting technology area. As a rule of thumb ALLISS systems should only be purchased if 360 degrees of coverage is necessary. ALLISS is only used by well funded broadcasting and telecommunications operations that intend to use the modules over their design lifespan of 50–60 years.

Around US$10 million. Some modules have been rumored to cost as much as US$15 million. With 4 different module versions cost per module can vary by as much as US$5 million. At least 30% of the cost of each module is related to the still exotic metallurgy and metalworking requirements needed to construct each module. Because of the costly and complex metallurgy construction requirements, ALLISS technology is 'off limits' to many developing nations including even a few advanced nations in the developed world.

Typically ALLISS modules possess a 500 kW polyphase shortwave transmitter. Digital 'AM' type transmitters are preferred for their compactness. Many 'Push pull' (Class B) transmitters may be too large for some ALLISS installations. Essentially all 300 kW and 500 kW PDM, PSM, polyphase (4 x PDM) transmitters are preferred for structural reasons. It is not customary to install a 300 kW transmitter in an ALLISS module, but such installations are possible. TDF's Montsinnery Relay Station has 2 ALLISS modules installed, but without an installed shortwave transmitter. This same design arrangement is used by the BBC World Service Oman Relay Station A'Seela.

One Low Band antenna exists for Tropical Band broadcasting. It takes up the entire back side of the ALLISS module. This Low Band antenna counterbalances the primary transmission antennas used in traditional shortwave broadcasting.

The International broadcasting center of TDF (Télédiffusion de France) is at Issoudun/Ste Aoustrille. Issoudun is currently utilized by TDF for shortwave transmissions. The site uses 12 rotary ALLISS antennas fed by 12 transmitters of 500 kW each to transmit shortwave broadcasts by Radio France International (RFI), along with other broadcast services.