DIY Power inserter

[CRMS]

I understand that there is still an issue with unicable and recordings. The solution seems to be to keep the physical tuner, say Tuner A, powered on.

Is there a simple "cable power injector" solution? A simple DIY one as shown here - http://www.satcure.co.uk/tech/dc_inserter.htm

I'm assuming that the LNB is to the left. Power could be simply taken from the 12v supply to the receiver. Then whenever power to the receiver is on, the LNB is also getting power.

And I now think that the splitter I bought is actually a power inserter:

https://www.toolstation.com/proception-wideband-tv-satellite-splitter/p66100

DC goes in at the top, right hand bottom to LNB and left hand bottom to receiver.

 

[CRMS]

Just checked the so called splitter with a multimeter. And indeed the power pass does let DC to go along the dotted line. And nothing the other way. So bottom right to LNB and bottom left to receiver.

And the receiver only appears to have 13v on the Tuner A F male plug?? Tuner B F male plug is 0v??

 

[CRMS]

I think I have worked out the following:
Jess is a specific design and make of Unicable and is similar to Unicable 1 and 2. Made by Jultec. https://wiki.openpli.org/Unicable_/_Jess
Unicable LNB just requires 12-13v at around 350ma, so approx 4 watts. Power to GB receiver is 12v. So can be taken from power supply lead to the power INSERTER. No need for a 240v adapter.
Legacy LNB switches 2 voltages, around 14v and 18v. Done by receiver and takes less power.
I have 2 cables from my dish at home, so an LNB with Unicable 2 and a Legacy cable would work - I think??

Anyone heard of Maclean TV Systems Unicable 2 LNB??

 

[scouse645]

I got the sky power inserter today, fitted it and thought that's sorted it, i'm afraid not, tried it before my splitter then after it, still the same problem.

 

[CRMS]

That is not good to hear.
Think I'll try the DIY solution at http://www.satcure.co.uk/tech/dc_inserter.htm

 

[BrianTheTechieSnail]

That is not good to hear.
Think I'll try the DIY solution at http://www.satcure.co.uk/tech/dc_inserter.htm

That doesn't seem to mention any inductor to stop you losing the RF through the source of DC!
A capacitor to stop the inserted power going back towards the receiver might also be a good idea.
Similarly, further down, the one shown as a way of measuring the current doesn't show any capacitor to complete the circuit at RF frequencies.
However wrote this page didn't really seem to know what they were doing!

 

[Joe_90]

There's no direct DC connection to the plug end, Brian. The RF signal is capacitively coupled to the plug as described in the photos. It's all a bit "Heath Robinson-ish" but should work. Martin Pickering ran that website and shop for years and provided some excellent technical guides on electronics, aerials, cables and satellite connectivity. He retired to Crete some years ago. Still provides technical advice on Quora. Bit of an old curmudgeon and grammar nazi, but maybe that's why I always liked him!

 

[BrianTheTechieSnail]

There's no direct DC connection to the plug end, Brian. The RF signal is capacitively coupled to the plug as described in the photos. It's all a bit "Heath Robinson-ish" but should work. Martin Pickering ran that website and shop for years and provided some excellent technical guides on electronics, aerials, cables and satellite connectivity. He retired to Crete some years ago. Still provides technical advice on Quora. Bit of an old curmudgeon and grammar nazi, but maybe that's why I always liked him!

Ah. Designed to be buildable even if you don't have access to electronic components I guess.
Also no DC isolation if both your receiver and your dish are earthed. But that's relatively unlikely I guess.
Still nothing to stop the RF going out (or in) via the red and blue wires though.

 

[Huevos]

Ah. Designed to be buildable even if you don't have access to electronic components I guess.
Also no DC isolation if both your receiver and your dish are earthed. But that's relatively unlikely I guess.
Still nothing to stop the RF going out (or in) via the red and blue wires though.

I really don't understand what you are worried about. Are you a theory man looking for an inconsequential fault with this solution? If you are really worried that IF (not RF) might be leaking up the DC feed put a ferrite inline.

 

[BrianTheTechieSnail]

I really don't understand what you are worried about. Are you a theory man looking for an inconsequential fault with this solution? If you are really worried that IF (not RF) might be leaking up the DC feed put a ferrite inline.

When I tried to measure the current with a similar heath robinson solution I could not make it work. The receiver kept cutting off the power saying there was no signal.
I must admit I don't know if the problem was loss of signal or loss of screening meaning RF hash was getting in.
Just trying to point out that in my experience you will get nowhere with such a bodge method.

 

[Huevos]

When I tried to measure the current with a similar heath robinson solution I could not make it work. The receiver kept cutting off the power saying there was no signal.
I must admit I don't know if the problem was loss of signal or loss of screening meaning RF hash was getting in.
Just trying to point out that in my experience you will get nowhere with such a bodge method.

Sorry I thought you were talking about a proper solution such as the inserter sold by WoS.

 

[CRMS]

Just tried a GigaBlue Unicable LNB - 24 SCR, 2 Legacy.
Signal strengths - Unicable SNR 98/99%, AGC 8%, 16.0dB. Legacy SNR 99% AGC 97% 16.0 dB. Went through the Tuner set up correctly - I think. Signal strengths are better than elderly Universal LNB. So interesting that Unicable AGC is 8% and Legacy 97%.
Unicable is complete rubbish with continual "Tune Failed". Legacy is fine.
So tried power injection with 11.9v at the LNB. No signal at all?? Odd, so I'll bump up the voltage to 20v and see if that makes a difference.
Otherwise, grateful for any pointers??

 

[twol]

Just tried a GigaBlue Unicable LNB - 24 SCR, 2 Legacy.
Signal strengths - Unicable SNR 98/99%, AGC 8%, 16.0dB. Legacy SNR 99% AGC 97% 16.0 dB. Went through the Tuner set up correctly - I think. Signal strengths are better than elderly Universal LNB. So interesting that Unicable AGC is 8% and Legacy 97%.
Unicable is complete rubbish with continual "Tune Failed". Legacy is fine.
So tried power injection with 11.9v at the LNB. No signal at all?? Odd, so I'll bump up the voltage to 20v and see if that makes a difference.
Otherwise, grateful for any pointers??

Post tuner setup

 

[CRMS]

I'll have another go tomorrow. Back on Legacy. Test Match Special!!
But went through each FBC tuner - Cable to A, loop through to B, B External power Yes, Different band for each tuner.
Can also try splitting cable to A and B with 3 FB on each.
Seems that Vu+ might be the way ahead after all.

 

[Sicilian]

Just tried a GigaBlue Unicable LNB - 24 SCR, 2 Legacy.
Signal strengths - Unicable SNR 98/99%, AGC 8%, 16.0dB. Legacy SNR 99% AGC 97% 16.0 dB. Went through the Tuner set up correctly - I think. Signal strengths are better than elderly Universal LNB. So interesting that Unicable AGC is 8% and Legacy 97%.
Unicable is complete rubbish with continual "Tune Failed". Legacy is fine.
So tried power injection with 11.9v at the LNB. No signal at all?? Odd, so I'll bump up the voltage to 20v and see if that makes a difference.
Otherwise, grateful for any pointers??

Why not just use a proper purpose made power inserter? https://www.world-of-satellite.co.u...-gt-pi1-unicable-universal-lnb-power-inserter

 

[adm]

Just tried a GigaBlue Unicable LNB - 24 SCR, 2 Legacy.
Signal strengths - Unicable SNR 98/99%, AGC 8%, 16.0dB. Legacy SNR 99% AGC 97% 16.0 dB. Went through the Tuner set up correctly - I think. Signal strengths are better than elderly Universal LNB. So interesting that Unicable AGC is 8% and Legacy 97%.
Unicable is complete rubbish with continual "Tune Failed". Legacy is fine.
So tried power injection with 11.9v at the LNB. No signal at all?? Odd, so I'll bump up the voltage to 20v and see if that makes a difference.
Otherwise, grateful for any pointers??

Inserters with matching power supplies from other manufactures of unicable II LNBs suggest a 19V supply voltage.

Into which downlead are you injecting the power? It should be the unicable output and not the legacy.
When injecting power via an inserter is there a facility to stop the box also providing power to the LNB - the two power sources could be fighting each other?
How much current can your external power module supply - the spec suggests 300mA for the unicable side of the LNB ?

 

[adm]

Also, if you are using a power pass splitter it should be diode protected so voltage from one STB cannot arrive at the aerial socket of another that shares the same LNB. i.e. the voltage can only flow from the STB to the LNB but not in the opposite direction... and the STB itself should also have diode protection at the socket to prevent external voltage from entering it.

I assume that the STBs are already internally diode protected if by design they all can produce the unicable power to common down lead. It makes sense that the STBs all produce power because one or more boxes connected to a common down-lead (via splitters) could be switched off and the LNB still has to get its power from one of the STBs still switched on. The individual STBs don't know when someone is going to switch off another box on the cable.

The important part of your statement is that the power inserter must also have diode blocking on the power supply input because without a diode a power supply with a low source impedance would instantly drag down the voltage output from any STB if the external power supply was set to a voltage below what the STB would output itself. By design I would expect the STB to also be protected by current limiting its own output to what it sees as a virtual short circuit.

One question for my own education
In a unicable tuner mode do the STB boxes with multiple satellite input sockets produce the voltage on all these socket inputs all the time when the box is switched on or only when a tuner (or tuners connected to the socket by various internal means) is required for watching/recording?


With regards the DIY hacked power inserter mentioned elsewhere in this thread. It was not put forward on Satcure site as an alternative supply for unicable LNBs but more for getting power for other purposes such as providing power to a remote control extender (magic eye) or a head end amplifier on a terrestrial aerial system where the typically 5V from the terrestrial box could be switched off and 12V supplied from an external source . Note that the DIY solution doesn’t show F plugs but Belling Lee type connectors used for terrestrial TV. A hack designed for one purpose doesn’t necessarily work for different systems.

 

[CRMS]

Post tuner setup

Right had a another fiddle.
Satcure DIY DC power injector and 19.5v at Gigablue Unicable 2 LNB. When I last looked WoS didn't have any injectors but see them now in stock.
SNR 100%, AGC 7% and 16.4 dB. Don't think I can get better than that.

Tuner A



Tuner B to H as H. Each Tuner has own Channel, starting with Channel 1 for Tuner A to 8 for H.



Slight blank screen on Channel change.

Tried Tuner B equal to A, but CrossEPG wouldn't download - "CrossEPG error. Timeout for Tuner lock".

Now set 8 recordings and get picture break up and "Tune fail".

Perhaps as suggested in other posts, I should split signal to Tuner A and B and feed 3 FBC off each??

 

[adm]

Now set 8 recordings and get picture break up and "Tune fail".

Could this now be down to the quality of the cables you are using or the integrity of the cable now that you have cut into it to hack a power source? With unicable you asking more of the cable than with a TV aerial or a traditional LNB. Are you using a CT100/WF100 type cable with a full copper screen + screen braiding?

A hack into the cable may mean its no longer got a characteristic 75 ohm impedance and you are now getting reflections.

https://en.wikipedia.org/wiki/Signal_reflection

https://www.youtube.com/watch?v=zrDxSM91Jcg

 

[CRMS]

Cable is OK - copper braid, alu wrap, air core. Would have thought VSWR could be incorporated into software?? - my marine AIS receiver has a VSWR read out.

Now split the cable after the power injector to feed Tuner A and B - might as well use both of them as I've paid for them!! And 3 FBC tuners off each. Much better. SNR 99%, AGC 5% and 16 dB on both tuners.
8 channels merrily recording.