An update… to recap my mate was putting his FA antenna and Uputronics preamp on the roof and we were talking about connectors, adapters, coax, etc. In the end he stuck with the LMR400, grabbed some of the larger LMR400-ready SMA connectors and a right-angle adapter. This allowed it all to fit into an IP66 enclosure with both cables entering from underneath.
The right-angle adapter avoided needing a tight turn radius which would have put undue strain on the preamp’s SMA connectors. The preamp was mounted on a piece of wood which was sized to the enclosure, ensuring it wasn’t being supported by its SMA connectors. Then a load of glue to keep things in place and seal the holes. The antenna and box are mounted on the existing TV aerial pole above the height of the TV aerial.
The difference in numbers was immediate and he’s now getting over a million messages a day vs 7-800K messages before. Aircraft numbers are up around 300 a day and range has increased a little. His radar graph is pretty much 360 degrees now. Now we’re going to play with gain a bit but it looks about right from when it was in the attic.