Satellite Scan Information
Updated February 22, 2002

What is this?

The Satellite Scan system automatically scans the Ku band to confirm that known signals are indeed receivable. This is done to support the Horizon HDSM satellite meter, known in the US as the Birdog meter. The system currently scans from 61.5 west (Dish Network) through 127 west (Telstar 7) - we anticipate adding additional systems around the world to make this a global project.

The system uses a special Horizon meter with computer control, a Chaparral Monty 140 receiver to move the dish, a BLSA interface to perform spectrum scans and a modified DirectWay satellite dish with both FSS (11.7-12.2 GHz linear) and BSS (12.2-12.7 GHz circular) capability.

A scan is performed every three hours. The system points the dish at the appropriate satellite, selects the LNB using a 22KHz switch out at the dish and then runs through each known mux ensuring a lock is achieved. If the tuner locks, the signal strength is read - this is shown as a percentage just like Horizon meter. If the signal doesn't lock, the tuner is switched into "Auto FEC" mode where it determines the code rate. This is done since often uplinkers will change their coding rate without changing the symbol rate either to offer better signal protection or to increase the data rate without having to renegotiate with the satellite operator for additional bandwidth. If a lock still doesn't occur and the signal is less than 10MHz wide, the tuner will be stepped down 1MHz, then up 1MHz from the base frequency to compensate for frequency drift in the LNB.

Once each known mux has been checked, the system then uses the BLSA interface to measure the signal strength across the downlink band from the satellite - this results in a graph that looks very similar to what one would see when looking at the particular satellite with a spectrum analyzer. Once this has been performed on both polarities, the dish is moved to the next satellite and the scan continues. The data from each of the scans is saved and will be used for historical scans.

After all satellites have been scanned, the system sorts each satellite's lock results based on signal strength and then scans the list to find a unique transponder that won't lock anywhere else on the covered part of the satellite arc. This is to prevent false locks - for example, if we chose a 61.5w transponder that had exactly the same parameters as 91w, the meter would incorrectly identify a dish pointed at 91w as a dish pointed at 61.5w.

The system then takes this information and the spectrum scans and builds the HTML file that probably brought you here.

The Chart Explained

[This section needs a lot more work]

Green (which might be really dark green depending on signal level) means locked

Yellow means locked but the code rate changed

Red means no-lock. On the spectrum graph, dark red indicates that a carrier was found but there wasn't enough signal to lock the tuner.

Blue on the spectrum graph means the signal is known but not lockable by the Horizon meter - for example, Digicipher 2 or 8PSK.

Bold text on the mux list indicates the signal that's been chosen for the meter's database.

The DVBQ means DVB-S carriers with QPSK modulation. DSSQ means DSS (DIRECTV) carriers with QPSK modulation. IQ and QI signal spectral inversion - QI means the spectrum is inverted.

What about C-Band?

Thinking about this. Right now, the system is built to support the Horizon meter which can be used on C-Band, but typically is used for installing offset Ku antennas.

What about parsing the streams to identify programming?

Needless to say, looking at doing this with TSReader.

There appear to be a lot of known feeds missing, why?

Unless they're our only choice (Anik F1 and AMC2 for example), we avoid putting feeds in the chart since they obviously come and go and this isn't something you want when installing a satellite dish. We may add them when we start SI parsing with TSReader, but they will not be included in any data generated for the Horizon meter.

Is this a free service?

Depends. Everyone will get to view the latest 24 hourly HTML update for free. For more frequent updates and non-HTML data output (CSV and SAT files for the Horizon meter), there will be a subscription charge. How this is handled is to be determined.

Todo List

Change spectrum graphs to show strength across the entire band rather than 500MHz on that particular satellite. For example, Anik E1 is much weaker than the DBS satellites, but they still have the same graph scale.

Use the historical scan data to make signal over time charts.