New thoughts on repurposing old satellite receivers!

A project log for Streaming TV via a '90s analogue satellite box

Bringing a mid-nineties Sky Analogue receiver back to life in the age of Netflix

james-fosseyJames Fossey 03/04/2024 at 23:030 Comments

After a few months away, I've just thought of a more elegant way to repurpose an old, redundant analogue satellite receiver as a 21st-century 'channel switcher' for a Raspberry Pi streaming TV media centre.

My original 2023 idea (see previous logs) involved intercepting the IR signal from the receiver's remote. This did work, but it was a bit unreliable and felt inauthentic, because the streams weren't 'hard-wired' to particular channels on the receiver (e.g. using front panel buttons to change channels on the receiver would not change the stream - you had to use the remote).

My new 2024 idea is to instead use the switchable voltage from the receiver's LNB socket(s), piped through an analogue-digital converter (ADC), to tell the Pi which stream to select. Allow me to explain!

Most analogue satellite receivers can output two different voltages from each LNB socket: 17-ish volts and 13-ish volts, to receive 'horizontal' (H) and 'vertical' (V) polarised signals. In the analogue days, when you tuned your receiver to a specific channel (say, Sky One) you needed to tell the receiver which polarisation (and hence which LNB voltage) to use.

Later analogue receivers (mid-90s era) allowed two LNB connections, meaning two LNB sockets, and therefore you needed to specify one of four possible 'voltage combinations' to tune a particular satellite channel in the receiver's menu...which gives four voltage combinations:

Channel tuning setting in receiver menu
Voltage coming out of LNB1 socket
Voltage coming out of LNB2 socket
LNB1, V polarisation
13 volts
0 volts
LNB1, H polarisation
17 volts
0 volts
LNB2, V polarisation
0 volts
13 volts
LNB2, H polarisation
0 volts
17 volts

So, let's say I connect each LNB socket to a Raspberry Pi, via a suitable ADC converter**.

By programming 4 different 'dummy channels' on the receiver using each of the above LNB settings, and 'training' the Raspberry Pi to read the voltages from the two LNB sockets, I could use the analogue receiver to switch between four different streaming TV services depending on which voltage combination is being read by the ADC.

I haven't explained my thinking well, but I'd be curious to try it on a later analogue satellite receiver!

PS: Other ways of further doubling the number of unique possibilities may exist: e.g. specifying which decoder socket to use (on a receiver with two or more DECODER SCARTs) or adding an LNB 'tone' which was often controllable in the tuning settings.

**stepping down the voltage appropriately to avoid a massive 17-volt-induced bang