You are messing with IF after LNBF, in coax to receivers/switches.
There is a talk about tpns at satellite - totally different story !
['seperate' is wrong word, should use 'separate']
I am abundantly aware of that.
I design satellite uplink systems for a living.
I was specifically describing how the DirecTV LNBF's block convert the entire Ka band into two seperate (and quite frequency diverse) downlink IF frequencies, which they call "A-Band" and "B-Band".
IOW, I'm saying the same thing as you, and you misread what I said (I've edited the post a bit to be clearer).
I was responding to a specific question about their IF stacking scheme.
The fact that the IF downlink frequencies that the DirecTV system uses breaks the Ka band into two blocks that are many MHz apart, results in the receiver displaying the two IF blocks as if they were two "virtual" satellites, which the receiver calls 103(a) and 103(b).
Here's a PDF whitepaper from Zinwell that describes the DirecTV stacking plan. Note how they divide the Ka band into a "low" (b) and "high" (a) block (yes, they call the low "b" and the high "a"). The BBC then, takes the "B" band ("low" in the attached whitepaper) and shifts it up from the 250 to 750 MHz chunk that it comes down the wire as to a new block
above 2150 MHz (the highest frequency shown in the chart).