so ive been running a diamond x50a on the roof for about two years now and lately ive been noticing that my signal reports from the local repeater guys are down maybe 2-3 S units from what they used to be. nothing changed as far as i know, same radio (ft-7900), same coax run which is about 35 feet of LMR-400 going from the shack up through the wall and out to the mast. i re-terminated the PL-259 on the radio end last fall because the old one looked a bit corroded but i just used the same basic silver solder and a random connector from the parts bin.

my gut says its probably the coax connection at the antenna itself since i never touched that one and it's been up there through a couple winters. the antenna looks fine visually but i know that doesnt mean much. is it worth pulling the whole thing down to check or should i rule out other stuff first? also wondering if maybe the x50a just has a lifespan and mine is getting tired. these things dont last forever right

honestly the connector at the antenna end is almost always the culprit when this kind of thing happens. water wicks into a PL-259 real slow and by the time you notice it the center pin is basically green inside. pull it down and just cut an inch or two off the coax before you re-terminate, usually fixes it. LMR-400 holds up pretty well but the connectors are the weak point especially if whoever assembled it didnt seal it properly with self-amalgamating tape.

the x50a itself is pretty robust, ive had one going about 8 years with no issues, the radiating elements arent really going to degrade on their own unless something physically damaged them. check the connector first before you assume the antenna is shot. also worth doing a quick visual on the mast clamp to make sure the antenna didnt shift and mess up the ground connection somehow.

35 feet of LMR-400 on 2m is basically nothing, you're losing maybe half a dB there so the coax run length isnt your problem. definitely sounds like a mechanical/connector issue. the random connector from the parts bin thing jumped out at me - do you know what the actual spec on that connector was? some of the cheap silver plated ones that come in bulk bags are junk and dont make a solid connection at the center pin, especially after thermalcycling through a winter.