DIRECTV LNB Operation

Hi All,

I have a few questions which I've had trouble finding answers for. I don't know much about the specifics of a DIRECTV system's operation, so any links to a decent overview would be nice.

Unnecessary Background Information:
I have an SDR that can handle the IF output from the DIRECTV LNBs, and I'm looking to measure received power spectrum from DIRECTV satellites over time to analyze the effects of weather on signal strength. I'm not interested in demodulating the signal or streaming anything, so I don't plan on getting a DIRECTV receiver. I'm looking to purchase a Slimline Dish, LNB, and a power inserter from Amazon to look at the T10/T12 transmitters at position 103. I'm trying to decide if I should just build my own LNB or not at this point.

The Question:
Will an LNB and power inserter output the IF without a DIRECTV Receiver present? Is the receiver necessary to pass instructions back to the LNB? I got the impression from somewhere that receivers send commands back to the LNB to select the channels, (at least in the SWM configuration).

I've been trying to find drawings of the RF downconversion chain in the LNB too to see if the amplifiers implement some kind of gain control or if they're fixed, but I can't find anything. I suppose I should just buy an LNB and check it out myself by sweeping the power in and looking for a linear change in the output.

If there's a better place to ask this, please point me in that direction, thanks!

 

Yeah, I knew there wouldn't be much room and that I'm not getting any coding gain. I'm also aware that the satellite's transmit power is ambiguous since I'm simply looking at a received signal, so I've limited my expectations more to monitoring shallower fades on a shorter time-scale from effects when it isn't raining, namely tropospheric scintillation which is typically less than 2 dB. I'm hoping that this will also allow me to avoid issues with satellite transmit power variations depending on whether or not the sat's solar panels are in the sun.

It definitely makes sense to me that the older non-SWM LNB would be best here. When you say "feed it the appropriate voltage/tone" does that imply that the LNB needs something fed in besides just the DC from the power inserter? If so what would that be?

 

Haha, very true if there's an AGC, I may as well just brassboard my own LNB and go from there. I can't find any documentation saying if there is or isn't one though. I know they're very common in superheterodyning.

I have fallen into a trap of dealing with proprietary information, and I fear I will know nothing for certain without just buying crap and testing it.