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Normal Topic Finding a satellite with spectrum analyser (Read 1207 times)
Eric Johnston
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Joined: 3rd Jun, 2017
Finding a satellite with spectrum analyser
5th Jun, 2017 at 10:33am
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I have just had an email from someone having problems finding a particular satellite and wanted carrier.

Here are some hints.

First check that your LNB is powered ON and that the noise floor from the LNB is getting through to the spectrum analyser and receiver input.

Set the analyser to very wide span and you should typically see a raised L band noise floor from 950 - 2050 MHz.  If the spectrum only shows a line across the bottom then maybe the LNB has no DC power supply or the cable connectors are bad.

Set the dish elevation accurately using an inclinometer. Then swing boldly sideways till you detect something.  Look carefully along the top of the hump.

An initial detection may look like this.  Once you see tiny carrier spikes, stop and investigate.

Once you have detected a satellite peak up using small movements in azimuth and elevation. 

Expect a peaked up C/N of about 10 to 20 dB, as above.

Note that at this point you do not know which satellite it is.

To help identify the satellite narrow the span to look more closely at the carriers.

In this case about 800 MHz span is fine.

Looking at this you may recognise the pattern as being from a particular satellite.  Noting the frequency, bandwidth and number of the largest TV carriers is recommended. Lyngsat publishes lists of carriers.

Look more closely where your wanted carrier should be. Set the centre frequency to the wanted carrier frequency and the span to more than the wanted carrier bandwidth.

Is your carrier there ? If not check the other polarisation.

If you have not found, it your calculations about frequency are wrong or you need to go and look at the next satellites either way along the orbit. The next satellites will be along the sloping line of the geostationary arc.

When you calculate the L band frequency make sure you are using the true LNB local oscillator frequency. Check the model number and if the local oscillator frequency changes with voltages, tones or other signals from the receiver.

Many C band LNBs make the L band spectrum inverted.

Remember: Never transmit until you are absolutely certain you can see the wanted carrier and have got permission from the satellite network operations centre.

Best regards, Eric.
« Last Edit: 8th Jun, 2017 at 10:47am by Admin1 »  
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