petermcg:

 

Hi there I have had to replace my sat box on my second tv as I lost some channels. 
The no 1 tv has inbuilt freeveiw and works well, it works with LNB 12750 on KU band and through optus d1, and gets all the channels.  
So the new box i got for my second TV, I have managed to tune in, all the channels but with great difficulty and a lot of time. LNB is 5150 on C band and through multiple random satellites, but not including optus or koreasat. 
Do you think I am doing something wrong and what can I do to make everything work through our new satellite.

 

I should add that both setups are connected to the same small dish.

 

Even when a dish has multiple LNBs they usually have the same local oscillator frequency.  So if 12750 is working on one, then it should be the same on the other.  But 12750 is an LO setting that I have never met, so I am suspicious that it might not be correct.

Unless your TVs have had a firmware update or phone home for satellite data, they will not have the correct Koreasat 6 settings.  And old Koreasat 6 settings from when it was over Korea will be worse than useless.  As will Optus D1/D2 settings.  But the way most DVB-S/S2 tuner software works, if you can get the TV to see one multiplex correctly (using the correct LNB LO setting), then the software will read the NIT tables being broadcast on that multiplex and get the other frequencies to scan from that data.  If you have the LO setting wrong, then the numbers in the NIT table will not work and you will not get the other multiplexes tuned in.

The way LNBs work is that they have a local oscillator in the LNB that produces a signal that gets mixed into the signal incoming from the dish.  The signal from the dish is way too high a frequency for any sensible tuner electronics to be able to work with it, and it is so high a frequency that it does not run down cables properly either (it needs special "wave guides").  Mixing in the LO signal causes a heterodyne effect, so you now have the dish signal plus the LO signal and the dish signal minus the LO signal available as well as the original signal.  The dish signal plus the LO signal is even higher frequency but the dish signal minus the LO signal is a frequency that your DVB-S/S2 tuner can work with and will run down appropriate cables to the tuner.  So after the mixer there is a filter circuit that blocks all the higher frequencies that are now not wanted, leaving just the wanted dish signal minus the LO signal.

If you get the LO setting wrong, then instead of all the frequencies for the wanted multiplexes being in the range that your DVB-S/S2 tuner can handle, some may be too high a frequency or some may be too low a frequency and they can not be tuned.  As well, the frequency the tuner sees the multiplex on will not be the one that is expected, and it may also be being received off centre, so it is received badly.  And when the tuning software tries to find a multiplex by the frequency in the NIT table or some other source of the frequency numbers (such as the numbers for the satellites in its firmware), it will not be found there.

If your dish is an ex-Sky dish, then it is likely to have an LO setting of 10750 or 11300.  There are also a number of non-Sky dishes that use those LO settings also, so it is usually best to try them first.  Otherwise, you may need to work out what your dish and LNB is in order to be able to find the correct LO setting.  Sometimes it is on a label somewhere or embossed on the LNB.  But if it has been up there a while, any label may now be unreadable.

Most NZ dishes have single or dual LNBs, and the software in tuners rarely has an NZ setting that matches them.  So you usually fudge it using a different setting, such as "Universal" or "Ku band", and putting in the right numbers to do what is needed.  For Freeview and Sky you normally set them up using a setting that has three numbers: the low LO frequency, the high LO frequency and the frequency to switch between the two local oscillators.  The NZ LNBs usually only have one local oscillator, so the correct settings for those three numbers for a 10750 oscillator would be: 10750, 10750, 99999.  The 99999 for the switch frequency prevents ever switching to the high local oscillator which is not there.  The order of the numbers on screen can be different from "low,high,switch", so read what the software says about the fields.

In later Sky dishes, "switching to the high oscillator" actually switches to a second LNB pointed in a slightly different direction to pick up a backup satellite at 156E instead of the main satellite at 160E.  The switching signal is a 20 kHz tone that is sent by the DVB-S/S2 tuner card to the LNB.  If that 20 kHz signal is being sent by anything connected to the LNB, the dish will be using the 156E LNB (if there is one), so when you have multiple TVs or DVB-S/S2 receivers connected to the same dish, you have to make sure that none of them are sending 20 kHz tone due to bad LNB settings.  So it can be a good idea to disconnect all TVs/receivers from their aerial cables except the one you are trying to get tuned in.