I have a run of about 150 feet of LMR400 (specifically, it's this DX Engineering "400MAX" product). It connects to an Ed Fong antenna (2m, 1.25m, 70cm tri-band J-Pole) about 75 feet up a tree.
Here's what the SWR for the antenna looks like when measured directly (no feedline):
Here's what the SWR looks like when measured with the 150 feet of LMR400:
Here's what the LOGMAG measurement for the feedline looks like (notice about ~3db loss at 2m, and about ~6db of loss at 70cm):
I also tried this antenna+feedline empirically, and I can only reach 2 powerful repeaters that are right near me, I'm not even hearing miscellaneous APRS beacons around me which I receive with a small antenna near the ground. And when I send my own APRS beacon on 2m, no one (not even the close repeaters) hears it.
Notice that there is MAJOR loss, not just at 440mhz but even at 2m where I would have expected only about ~2db of loss with a high quality feedline like this. This is my first time using such a long feedline on such a high frequency, so I'm not sure if this is normal.
I emailed DX Engineering with these photos and asked their thoughts, and they said this is a normal amount of loss at that length.
I'm considering replacing half of the feedline with 300 ohm ladder line (with 4:1 baluns on either end) to see if I can bring down the loss, but before I do that I want to understand if this feedline could be faulty or something.
One thing I already tried was replacing both of the connectors with new ones in case they were faulty, but the results were identical.
Any thoughts? Thanks.