I have
I have several Uniden analog receivers, I don't think any of them would allow you to turn off the lnb voltage. I might be wrong but I don't think the 4400 or 4400 supra or the supra or any of the Unidens I own will allow you to do that.
You can get a slave kit from Sodoun to slave two receivers up...
I did a lot of research not long ago showing the connections for loop out or loop through. You can do it one of two ways depending on what receiver you want to the master.
One method was to connect the C-Band lnb to the Digital Receiver
Connect the loop through to the Analog receiver. going to the LNB port on that receiver.
You have to make sure of your connections otherwise you can damage both receivers. I did several searchs using google and found several connection options.
I used the above method without issue keeping in mind I used the 2 video ports on my TV to view each receiver. I would also turn the receiver off that I wasn't viewing.
I would strongly recommend you research this before making any connections because you can damage your receivers or lnb if not configured correctly.