Standard Tuners, and FBC Tuners, Universal LNB, and Unicable LNB

[JonMMM]

Trying to get my head around this before I give advice elsewhere. Is based on single satellite systems. Please feel free to comment / correct my errors

How The signal is split

Satelite singnal comes 2 pairs Horizontal (H)/ Vertical (V) and Positive (P) / Negative (N). So there are effectively 4 signal areas HP, HN, VP and VN.

Each channel is on a transponder, each transponder is on area as above.

Universal LNB

The old LNB that we all know, can have 1 to 8 outputs with each output having access to 1 transponder.

Unicable LNB

Only has one output (although may also have additional Universal outputs) These combine the 4 areas (as above) into one sending it all in one cable (think of this in the same way as a terrestrial aerial) you can then use splitters to spider around the house, e.g. you could have a 3 way splitter for 2 inputs to your receiver and 1 to your TV. Its a much neater solution.

Standard Tuners

Each Tuner needs its own feed to the LNB, and is capable of watching / recording all channels on the same Transponder (need verification for this)

FBC Tuners with Universal LNB

These have 2 physical inputs for there 8 tuners, you can either have 1 or 2 feeds coming from the LNB with the other 6 or 7 virtual tuners being fed from the same input. These tuners have quite an advantage even with a Universal LNB in that the virtual tuners are not limited to just the same transponder as the lead tuner but instead can access a whole area as described above. This means with 2 feeds you can watch / record around 50% of the channels available to you.

FBC Tuners with Unicable LNB

You only need a single feed but can use 2 if you prefer, the virtual tuners will pick up the signal from the physical but then act independently, this gives all tuners access to all available channels on the satellite.

 

[Trial]

Hi,
almost:
How The signal is split
The areas are normally called horizontal, vertical, high and low

Unicable LNB
The tuner send a signal which transponder he likes to have and this transponder is then put onto the line.

FBC Tuners with Unicable LNB
Unicable with standard tuner also has access to all available channel on the sat. The difference is that you can watch/record up to 8 transponder (around 40 channel) and with a normal dual tuner only 2 transponder (around 10 channel).

Ralf

 

[Huevos]

Horizontal/vertical

If you pop the cover off an LNB you will see 2 small pins, 1 horizontal and 1 vertical. These pins are the receiving aerials. If you pop up to the orbiting satellite and you look at the transmitting aerial you will see something similar to these 2 pins. Because these pins are at 90º to one another the signal sent by the vertical pin on the satellite can be received by the vertical pin at the LNB but is almost invisible to the horizontal pin. This allow the satellite to re-use the same frequencies in each polarisation without interference, thereby doubling the throughput of the satellite. The horizontal and vertical signals are identical, so inspecting what is coming down the cable it would be impossible to tell if the signal arrived via vertical or horizontal polarisation. i.e. polarisation is just a physical thing.

Ku band

This is the band we are attempting to receive. It covers 10700 MHz to 12750 MHz. So in total 2050 MHz of bandwidth.

Frequency range of the tuners

Standard tuners and FBC tuners cover 950 MHz to 2150 MHz. So in total only 1200 MHz. Damn, that is not enough for the 2050 MHz required above.

LNB (Low Noise Block converter)

This converts high frequency sent by the satellite to lower frequency in the range the tuner can handle. Called Low Noise Block converter because it converts a complete block of frequencies, not just one.

Universal LNB

There is a 1 to 1 relationship between tuner and LNB socket. To control the LNB properly there can be a maximum of just 1 tuner per LNB socket. The Universal LNB has the 2 physical pins mentioned above, one for each polarisation. To switch the LNB to vertical mode the tuner supplies it with 13 volts. To switch to horizontal mode the tuner supplies the LNB with 18 volts. So now we have the problem of the 2050 MHz of bandwidth of the Ku band not matching the 1200 MHz of bandwidth of the tuner. To deal with this the LNB splits the band into 2 section, high and low. The tuner has to tell the LNB which it requires for the current channel. If it requires low band it sends nothing to the LNB, and if it wants high band it sends a continuous 22 kHz signal to the LNB. So now we have the 4 phases of the LNB, 1) horizontal low (18v and no 22 kHz), 2) horizontal high (18v and 22 kHz tone), 3) vertical low (13v and no 22 kHz), 4) vertical high (13v and 22 kHz tone).

Unicable LNB

So Universal is a bit wasteful because it is sending the whole block down the cable, maybe around 32 transponders when we only need one. And we have the added problem that we need one cable for every tuner (we can't share). And in loopthrough mode we can only access channels on the same sub-band as the principal tuner. So Astra invented Unicable. It had to be able to work with all current receiver hardware with just a software update to the receiver. So instead of sending a whole block of frequencies it sends just one, the desired one. The receiver sends a digitized instruction to the LNB using the same 22 kHz tone used by Universal, and the instruction says I want this frequency, and this polarisation and send it down the cable on this SCR (frequency). Now only one frequency is being sent there is plenty of space left on the cable to send other frequencies to other tuners/users across the same cable.

FBC tuners

One tuner module is able to tune up to 8 frequencies from 2 different cables. There is no such thing as a virtual tuner. This is just a software trick in the drivers to get it to interface with the 15 year old enigma project.

FBC with Universal

Acts as 2 principal tuners with 6 loopthroughs, i.e. if you tune 8 transponders all must come from no more than 2 blocks, as we only have 2 cables and each cable can only carry one block.

FBC with Unicable

Share one cable between all user/tuners. Can tune up to 8 frequencies similtaneously irrespective of polarisation or high/low band. Plus the same LNB can be shared by other receivers as long as these are configured on other SCRs (frequencies). In blocks of flats each residence is limited to its on SCR by a programable filtering wallplate. This stops the resident configuring their receiver to use someone else's SCR.

 

[adm]

Unicable with standard tuner also has access to all available channel on the sat.

Pedant mode: so does a single output universal LNB and standard tuner

 

[adm]

Horizontal/vertical

If you pop the cover off an LNB you will see 2 small pins, 1 horizontal and 1 vertical. These pins are the receiving aerials.

Minor info only See photo 3

www.admac.myzen.co.uk/quad_lnb