Keeping an earth station on air in winter

A satellite link that has run all summer can lose several decibels in a single night of freezing rain, and the first sign is usually a support call rather than an alarm. Winter degradation is gradual, invisible from ground level, and entirely preventable.

What ice actually does

Three separate effects stack up, which is why the loss is often worse than people expect.

• Absorption. A wet layer on the reflector absorbs signal. Wet snow and freezing rain are far worse than dry powder, because water absorbs and ice alone largely does not.
• Surface distortion. An uneven accumulation changes the reflector profile. A parabola only focuses while it is a parabola, and the tolerance is a fraction of a wavelength, which at Ku and Ka band is millimetres.
• Feed and sub-reflector blockage. Ice builds first on the smallest, most exposed parts, and those sit directly in the signal path.

The higher the band, the less it takes. A Ka-band station is affected by accumulation that a C-band station would barely register.

Why de-icing is a power problem

Heating a large reflector enough to clear it is straightforward if power is unlimited. It rarely is. A remote site on generator or solar cannot support a heater sized to melt everything on contact, and running one continuously through a season is expensive even where grid power is cheap.

The design goal is therefore not maximum heat but minimum energy for a reliably clear surface. That means heating the areas that matter, in the conditions that matter, and only then. Our de-icing systems are built around very low power consumption for this reason, sized to the antenna, the climate and the power budget of the site.

The rest of winter readiness

De-icing is one item on a longer list. The others are cheaper and are usually what fails first.

• Drainage at the feed and at every waveguide low point, checked before the first freeze
• Radome seals and boots inspected for splits that summer heat opened up
• Cable entries resealed, since ice will find every gap
• Positioner lubrication rated for the actual minimum temperature, not the average
• Guy wires and mount bolts re-tensioned after the summer expansion cycle
• Ground and lightning protection verified while the ground is still workable
• A spares kit on site, because the access road is the first thing to close

Instrument it, then you will know

The most useful winter change is not hardware. It is trending the receive carrier-to-noise ratio for every site and alarming on gradual degradation rather than only on carrier loss. A site losing a decibel a night over a week is telling you something well before it drops. That is ordinary work for a network management system that already collects the figures, and it turns a support call into a scheduled visit.