Copied from that post:
"3 units into one antenna through an RF Systems RF Splitter to present equal match to all boxes showed that the SBS-1e consistently over a 24 hour period gave 2 or 3 aircraft more than the other 2 units. Due to the way ADSP is handled it is meaningless to publish figures about db etc. "
On this post they mention that they didn't do any lab tests to compare the units. They were simply put side by side with the "same" conditions (with an antenna that matches SBS and not RadarBox). This is, as you may understand, a non professional way to compare the units and to promote a product using something that it does not have (increased sensitivity).
If you take a single antenna, then split the output via a 50 ohm splitter that provides the correct impedance for each receiver and gives isolation between each pair of receive ports then there is simply no better way of comparing several receivers as each will be provided with exactly the same signal to demodulate. The loss of range due to the splitter will be the same in each path, so it is an entirely fair comparison.
The results may be different in different locations however, the received signal levels and number and relative position of aircraft may well cause the different receivers to behave differently.
Nothing in this world can be distilled down to "A is always better than B", there are always caveats. But a large number of comparisons at different locations should enable a "most of the time" comparison to be drawn up. It would be possible to do this for a number of different antennas too, to establish whether any particular one benefited a particular receiver.
