6 months or so ago I decided I wanted to upgrade my satellite setup to get both polarities of Optus D1 and D2, and Intelsat 5 if it was possible. The results of this decision so far have meant nothing but headaches for me! In short, the multiswitch and dual output LNBs I bought didn't seem to want to play ball with my HTPC. I thought they either didn't provide enough signal or compromised the signal quality (...or that I had wiring issues...or that I had dish alignment issues...or that I had received faulty LNBs...or that I had driver problems......the list of what I have investigated goes on, but you get the idea), and I have been tearing my hair out trying to get to the bottom of the issues. The worst thing about it has been that the issues have been inconsistent/confused and I haven't had the time, tools or knowledge to really troubleshoot the problem/s properly. It's a long story so I won't bore you with the details. Suffice to say that I think I have finally found the source of the problem: my HTPC TV card's output voltages.
The HTPC is putting out approximately 14.5V for vertical and 20.5V for horizontal. As you might guess, the vertical voltage is smack bang in no-man's land for the dual output LNBs (spec: 11.5-14V and 15.5-19V for vertical and horizontal respectively). The resulting symptoms were severe dropouts on vertical transponders probably caused by the LNB switching between vertical and horizontal or being unsure which polarity to supply. There were also occasional glitches on horizontal transponders (worse on high frequency transponders), but Freeview channels especially on 12456H were absolutely watchable. As far as the multiswitch goes, it is unclear what the input voltage specifications are (output is perfectly within spec so other STBs are usually okay) but I'm guessing the same issues apply because the same symptoms can be observed. The clincher is that when you plug in other LNBs with looser/different input voltage specifications you get perfect reception. For example, a Zinwell ZKF CH21 gives *almost* perfect reception with a glitch every minute or so at most.
As you might imagine this has led to the almost perfect storm of confusion because none of the symptoms made sense. Some LNBs work fine, or one polarity works *almost* perfectly etc.
My question: is there a way to [safely] reduce the output voltages of my TV card?
The first thought that came to me was to insert a resistor inline with the HTPC between the card and the multiswitch, but I'm not sure if this is appropriate given that it could cause impedence mismatches. I'm also not sure what value I should use because I'm not sure of what current the TV card is producing.
Ideas and suggestions would be much appreciated!
On a different front, this gives me cause for concern about my other PC components. I mean what if this issue is really caused by my power supply voltages being too high (or even out of spec). If this is the true cause, is there anything I can do to "fix" it?
Thanks in advance :)