@alan4160 please ensure when you have the transmitter connected to one end of the cable, the other end of the cable is disconnected. When you run the probe up and down the transmitter end of the cable when its connected in the basement, does it beep, due to any ability to receive the signal outside of the cable jacket? You might have to increase the probe sensitivity to do this. If so, then you might have the ability to follow that cable within the wall. Don't run the tests solely at the wallplate locations.
Due to the splitter buried in the wall, you would have to do this from both ends of the cable. That splitter will decrease any RF energy in the cable when you cross over to the other side of that splitter, so, you really have to treat each wallplate location as a cable section on its own, running the test from each wallplate, moving in the direction where the splitter should be. What I'm hoping is that with the transmitter connected at each wallplate, that will give you the ability to follow the cable (in the wall) when the probe sensitivity is turned all the way up.
In the room where the modem is located, connect the transmitter, and with the downstairs cable disconnected, see if you can detect that transmitter anywhere around the wallplate. If you don't know which direction that cables arrives from at the wallplate, don't assume that it goes in the direction of the basement cable. With the probe right at the wall, sweep all around the wallplate , moving further and further away, and see if the probe can detect the direction that the cable goes. You may have to go up the wall as well, depending on where that cable might go. Turn the sensitivity all the way up so that the probe beeps very loudly at the transmitter site. Keep the sensitivity turned up and hopefully the probe beep will gradually decrease as you move away from the transmitter and keep beeping as you follow the cable path along the wall.
Try this at all wallplate locations to see if you have any success anywhere in the house. Keep the basement tan cable disconnected. For the upstairs wallplate, maybe they come straight down to the room below? So you would have to check all around the upstair wallplates with the probe, and perhaps immediately below that location, on the wall that is just below that upstairs wallplate.
If this just doesn't work, the next step would be to call in a company that has a better detection system. This is only powered by battery, so, perhaps it takes a powered system to generate enough RF energy in the cable so that it can be detected behind the wall.
Can you give this a try and let me know if you have any success at all? I'll be very interested in your results. I'm really hoping that the probe is sensitive enough to be able to detect the cables in the wall, but, you're going to have to run that probe right next to the wall to have any success.
Edit: For the wallplate upstairs where you didn't detect anything, take the wallplate off of the wall and see if the cable is connected to the wallplate. If its is, that implies that the other end of the cable was simply removed off of the splitter, or, it may have been cut. I'm hoping that it was removed from the splitter. If so, that far cable end should function as a small antenna. You might be able to detect that end, wherever it happens to be. In theory, those upstairs cables should arrive at a splitter upstairs, or downstairs on the main floor. Hopefully those ends are all on the main floor. I would test all of the upstairs wallplates where you did not detect anything, looking to find the other end of the cable.
If you do manage to find a potential splitter location, buried in the wall somewhere, are your walls made out of drywall, or is your home old enough that its has lath and plaster walls?
Hi @alan4160 the signal levels with the two MoCA splitters might be 1 db less than the signal levels without the splitters. In your case, it won't make any difference as both of those series of signal levels are fine. You wouldn't see any difference between the two configurations in terms of the cable system operations, unless that lost splitter comes into the picture. With that lost splitter in the path, a db or two here or there can make a difference in the very far end equipment. Typically, that db or two wouldn't make a difference.
For the frequencies above 800 Mhz being negative, their not too bad actually. I've seen much worse. That due to a High Frequency roll-off that occurs in some neighbourhoods. Some of the equipment in the neighbouhood requires replacement with higher frequency capable equipment. That also includes cabling in some cases, such as RG-59 cabling in homes.
