The original thread I saw on slaving a receiver was about an analog receiver and it suggested using a DC Block. I thought the same logic applied to all receivers so I've continued to use one to be safe. I have noticed some quirks when I've used the Coolsat as a master but am glad to know about the Fortec. Good luck!
In my opinion, there is no difference between analog/digital relative to the logic with respect to using a DC block. I absolutely NEVER connect the inputs of any two receivers without using a DC block. In fact in one case I needed to use TWO DC blocks to get things to work right (must admit that I don't understand that one).
The simple reason for using a DC block is that when you have 2 receivers, both of which are putting out DC voltage to power an LNB, it simply isn't worth the risk of the two DC power supplies fighting each other, and possibly doing damage to one of the receivers.
In SOME cases, FTA receivers with passthru's MAY incorporate DC blocks in their design to protect their circuitry, and MAY stop their voltage from getting through to receivers connected further down the line, but as has been mentioned above, unless you have the schematic for the receiver, there is no easy way to tell what is going on in the passthru.
I have seen posts from people who have used the passthru without a DC block. These people were careful to not have both receivers on at the same time, and they were able to control the LNBF polarity by the DC passing through the passthru, only when the master receiver was switched off.
Without schematics, there is no way to tell for sure, but my impression is that some passthrus are simply that, simply something like a splitter that the master taps off, perhaps with a DC block to avoid interaction of the DC voltages, perhaps not. However other passthrus are definately amplified. Ie the signal comes into the master, and then after the master extracts IT'S signal, it runs the signal through an amplifier so that the slave receivers often get a higher signal level (and higher noise) that the original signal. If you don't use a DC block on an arangement like this, you are feeding DC voltage into the back end of an amplifier stage. I just can't imagine anything good coming out of that.
Anyway, I use passthrus all the time. At times I have had 5 or 6 different receivers fed off the same signal using 1 splitter and 3 passthrus. However I ALWAYS use DC-blocks between every connected receiver. It's just not worth the risk of damaging something. I also tend to not trust those one leg power passing splitters, because I have found that some of them are not completely DC-blocked, particularly if you happen to hook up the receivers to the wrong ports accidently, which I did once, which ended up sending DC voltage back into one of my computer card receivers, which ended up putting my computer into one of those blue screen of death things (it eventually recovered).
Some people connect receivers without DC blocks, and don't have any problems, but I think this is really receiver specific, and eventually they will try this with a receiver that has a passthru with a different design, and it will end up causing damage.
Just my opinion.
