Zilog80
03-25-2011, 10:05 PM
Here’s a trick I used a few years ago when I first played with digital IRD’s on my old C-Band dish. Back in old C-Band days LNB’s could easily cost upwards of 500 bucks and were often hard to get. Not like today when you can buy most types of LNB’s off the shelf at most FTA dealers for less than 50 bucks. Electrocuting them could be expensive.
So I wanted to leave the power alone that was being fed from my old analogue receiver out to the dish. But at the same time I wanted to pick off the L-Band feed from the big mesh monster and look at it with the brand spanking new Pansat.
I was worried about a conflict between the power from the analogue IRD and that from the Pansat. In retrospect I now know two things about this worry. One is that either IRD could supply the voltage needed out at the dish without hurting the LNB. The other was that I could have fed the picked off signal from the old system into the IF loop out of the Pansat and avoided a power conflict as it does not supply power on that port.
But rather than have a “one or the other” design I wanted both, (There were still lots of analogue to watch back then. Like NASA for example.), and to be able to tune across the C-band with the digital IRD independent of the old Analogue.
So here is what I did. I made myself an L-band Splitter out of an old TV splitter.
I grabbed a TV splitter and pried the back off it. Inside there are all sorts of stuff, coils, caps and things like that. I stripped the works out leaving only the three F-connectors attached to the box. (You cannot just use a normal TV splitter if you have not already discovered this.)
Then I added a new wire from the common F-Connector to one of the splitter output F-connectors. This becomes the power feed side of the splitter so you connect the LNB to the common F-connector and the receiver or IRD to the F-connector with that new wire on it. Now an important step.
Turn the splitter over and mark a big black line between those two F-connectors so you can see which ones they are when you connect things up. (Assuming of course you will be putting the back on the splitter once again.)
Finally connect a capacitor between the common or single F-connector (now with a wire soldered to it) over to the un-used F-connector. This will be the connection used to pick off the L-band signal and feed it to your digital IRD. The capacitor acts as a DC block preventing the digital IRD power from conflicting with the voltage from the old analogue receiver. Use a 50 pf capacitor or there abouts. Not too critical and it only affects the signal strength somewhat.
One other note. In my old analogue system the polarity of the LNB is controlled by the analogue receiver and therefore it means you need to manually flip the polarity as you scan away with the digital receiver. Most channels seem to be on the horizontal polarity but some of the “good stuff” is over on the vertical.
Z
So I wanted to leave the power alone that was being fed from my old analogue receiver out to the dish. But at the same time I wanted to pick off the L-Band feed from the big mesh monster and look at it with the brand spanking new Pansat.
I was worried about a conflict between the power from the analogue IRD and that from the Pansat. In retrospect I now know two things about this worry. One is that either IRD could supply the voltage needed out at the dish without hurting the LNB. The other was that I could have fed the picked off signal from the old system into the IF loop out of the Pansat and avoided a power conflict as it does not supply power on that port.
But rather than have a “one or the other” design I wanted both, (There were still lots of analogue to watch back then. Like NASA for example.), and to be able to tune across the C-band with the digital IRD independent of the old Analogue.
So here is what I did. I made myself an L-band Splitter out of an old TV splitter.
I grabbed a TV splitter and pried the back off it. Inside there are all sorts of stuff, coils, caps and things like that. I stripped the works out leaving only the three F-connectors attached to the box. (You cannot just use a normal TV splitter if you have not already discovered this.)
Then I added a new wire from the common F-Connector to one of the splitter output F-connectors. This becomes the power feed side of the splitter so you connect the LNB to the common F-connector and the receiver or IRD to the F-connector with that new wire on it. Now an important step.
Turn the splitter over and mark a big black line between those two F-connectors so you can see which ones they are when you connect things up. (Assuming of course you will be putting the back on the splitter once again.)
Finally connect a capacitor between the common or single F-connector (now with a wire soldered to it) over to the un-used F-connector. This will be the connection used to pick off the L-band signal and feed it to your digital IRD. The capacitor acts as a DC block preventing the digital IRD power from conflicting with the voltage from the old analogue receiver. Use a 50 pf capacitor or there abouts. Not too critical and it only affects the signal strength somewhat.
One other note. In my old analogue system the polarity of the LNB is controlled by the analogue receiver and therefore it means you need to manually flip the polarity as you scan away with the digital receiver. Most channels seem to be on the horizontal polarity but some of the “good stuff” is over on the vertical.
Z