Very interesting. I have the TST 507 and from what I was told by TST, the need for a repeater will cause the sensor to drop off the screen, not stay on the screen and not report. I know this because when I went to the longer 35 ft trailer, I was having problems with sensors dropping off the screen and was told I probably need a repeater. I normally had the Receiver mounted low on the center console (worked fine with my old 25 ft trailer) and when I moved it up on the dash, I got better reception and never had another problem. That was almost 3 years ago.