so ive been running a 25ft piece of RG-8X from my IC-9700 up to a Diamond X50A on the roof and i keep second-guessing myself about whether i should just bite the bullet and run LMR-400 instead. the coax goes through the attic and makes a couple bends, nothing crazy. on receive the noise floor seems fine to me but im not really sure what i should be comparing it against since i dont have a reference setup.

the X50A is maybe 20ft above the roofline on a push-up mast, so total coax is probably closer to 35ft once i account for the attic routing. at 146mhz how bad is RG-8X really getting? i ran the numbers on one of those online calculators and it said like 1.1 db loss per 100ft so for 35ft thats what, not even half a db? but then someone at the club last week told me RG-8X is garbage and i should have used LMR-400 from day one. he seemed pretty adamant about it but wouldnt really explain why beyond just saying trust me.

not trying to work weak signal or anything serious, mostly just local repeaters and occasional simplex. is the cable swap worth tearing apart my attic run for or am i chasing ghosts here

your math is basically right and for repeater work you're genuinely not going to notice the difference. half a db either way on 2m FM into a repeater that's probably 20 over s9 anyway is just not a real world problem. the guy at the club probably just has an opinion and ran with it.

now if you were doing EME or weak signal meteor scatter yeah every tenth of a db starts mattering and you'd want the best feedline you could get. but for what you're describing i wouldnt touch it. save the LMR-400 money for a better antenna down the road if you want to actually improve the station, the X50A is decent but there are better collinears out there if you ever want to stretch a little further on simplex.

yeah i had almost this exact debate with myself last year, ended up leaving the RG-8X in place and honestly cant tell any difference on the air. the connectors matter way more than people realize too, a poorly crimped PL-259 will hurt you more than the cable itself at those lengths on 2m. did you solder the center pin or just rely on the crimp? asking because i had a flaky connection for months that i blamed on the cable and it turned out to be a cold solder joint the whole time.