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Nov 6th, 2012 at 10:18am
Rain causes significant attenuation of the signal at Ka band and the warm (approx 280K) rain also increases the noise temperature of your receive system.
To avoid loss of service during rain, the bit rate is reduced so as to maintain a good reliable service but at a lower speed. In your uplink it may also be possible to increase your transmit power level.
If the clear sky download carrier bit rate is 70 Mbit/s then the reduced speed for say 24 hours per year might be 30 Mbit/s. Note that this reduced speed only applies to download packets destined to customer sites experiencing heavy rain.
If rain occurs when the system is not busy with traffic then you are less likely to notice any speed reduction.
It is unlikely that you will lose service for more than a few hours per year, but it all depends on your particular weather and how well pointed is your dish !
The KA-SAT hub gateway sites (Makarios Larnaka, Cyprus; Rambouillet, France; Cork, Ireland; Arganda Madrid, Spain; Berlin, Germany; Turin, Italy; Scanzano, Italy; Udine, Italy; Athens, Greece; Helsinki, Finland) are also affected by rain. They have very powerful transmitters with considerable scope for increasing powers during rain, also their dishes are much larger, providing significant link margin for the reception of your tiny transmit bursts. Point your dish really carefully and its transmit bursts will get through better in the rain. Remember that your antenna beamwidth for your 30 GHz transmit signal is narrower than your 20 GHz receive beam so it is really important to get to the exact centre of the beam when lining up.
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