I'm connecting my Giniatech usb satbox to loop out of my Strong satelitte receiver (4653X) so I need to turn off the LNB power. I used the multimeter to measure the voltage of the RF IN and found out that it got same voltage (12V) regardless if the lnb power is on or off. I'm wonderring if it is a bug from progdvb or from the satellite driver. (I tried version 4.15, 5.15.8, 5.15.9 and it got the same problem). If I leave it like that will it damage my Strong receiver later on. Thank you very much.

I must ask Geniatech about this.

As far as I know, your Strong receiver (like any other with a loop port) should not have any problems with getting +12 (or 13) Volts on the LNB loop port. If not sure, read it's manual.
That 12 Volts also would not keep it away from switching polarisation or anything else.
Just if you insert 18 Volts there, this might prevent it from switching back to Vertical. And if getting 22kHz inserted over the loop, it is not supposed to be able, to remove this signal from the line to the LNB.
Details depend on the way the LNB ports are decoupled inside of the tuner. In most cases this is done by a Diode these days, resulting in higher voltage dominance. At that location, a relay instead, electronic or electromechanic, would allow, to completely ignore the loop port state, if the Strong was active, but the extra components needed would result in extra costs, manufacturers like to avoid in most cases. And what's not there can't degrade or fail...
This is quite similar to others not integrating a stage to switch off LNB supply in stand by.

However, feeding LNB voltage to the loop port must be electrically safe, as this will happen frequently. Else a loop port must not be there or permanently and completely decoupled from DC by just one cheapo chip capacitor...

Juergen wrote:As far as I know, your Strong receiver (like any other with a loop port) should not have any problems with getting +12 (or 13) Volts on the LNB loop port...

Did you mean that I shouldn't have any problem connecting the loop through port of my Strong receiver if my satbox has the power turn on? But one thing I doubt it may cause a problem is the loop through port of my Strong receiver gives 13 V when I tried to measure it whereas the other receiver that I got does have the voltage at all (they were both powered on when I measured the voltages). The following diagram may explain what is happenning

(Strong receiver loop through) ==13 V===> <== 13V === (Satbox RF IN)

Normally conflicts could only occur if one device provided 18 Volts for H but the other needed 13 Volts for V.
This in fact depends on the way, the decoupling inside of the loop through electronic circuits is really done. In many cases, the higher voltage dominates. Else the loop through device may disconnect the loop port DC path when it's tuner is set active. Manufacturer's design decision...

A digital multimeter would even indicate a very high impedance sensing voltage or some switch stage leaking voltage with a very limited current, or a still loaded capacitor, whatever may be the source of the backward voltage you have found.


But generally, all this is a normal situation, the devices have to be made for, as a typical STB will also come with a timer function, switching on and off in your absence. Regarding this, a computer controlled device is not different.
So, depending on the devices, you may get some switching trouble when sharing an LNB line, but there should not be any danger of electrical damage, based on this way of wiring.