Finally Tackled the Feed Line Mess — Upgrading to LMR-400

The final straw was when I started noticing my signal reports on 20m were consistently a little soft. Not terrible, but guys on the other end would say things like "you're Q5 but a bit down compared to others." And I knew my antenna was decent. I'd modeled it, I'd trimmed it, the SWR at the radio was reasonable. But something felt off and I kept coming back to that sad, weathered collection of coax running from my shack window out to the fence post and up to the antenna.

So I finally ordered a 100-foot roll of LMR-400 from a supplier I trust, a couple of PL-259 connectors rated for LMR-400, and a proper weatherproofing kit with self-amalgamating tape. Total came out to around $95 which, yeah, stings a little, but honestly I should have done this from the start instead of piecing things together.

The Old Coax Was Worse Than I Thought

Before I even started installing the new stuff, I cut open the end of that old RG-8X section near the barrel connector. The braid was greenish. Not like a little tarnish — actually corroded green in spots. And the center conductor had some discoloration too. I have no idea how long that coax had been sitting outside before I got it at the hamfest, but clearly it had seen better days. Water had definitely gotten in somewhere along the run. Lesson thoroughly learned: don't buy unmarked coax at hamfests unless you're absolutely sure what you're getting and plan to test it properly.

I checked the barrel connector too and found one of the center pin connections was barely making contact. Honestly the whole thing was one good rain away from completely failing. It's a little embarrassing to admit because I know better, but sometimes you just want to get on the air and you tell yourself you'll fix it "later."

Installing the LMR-400

LMR-400 is noticeably stiffer than RG-8X, which took some getting used to. Running it around corners and through the window feedthrough required a little more patience. I used a standard oval feedthrough plate that I'd installed when I built the dipole — gave myself about 2 inches of clearance so the coax could make a gentle bend rather than a sharp one. You don't want to kink LMR-400, it doesn't forgive you the way smaller coax does.

Putting on the PL-259 connectors for LMR-400 is a little different than for smaller cable. I used the solder type connectors, not crimp. There's a specific adapter/reducer that goes with LMR-400 and you have to prep the cable really carefully — strip the jacket back the right amount, fold the braid back cleanly, make sure the center conductor is long enough but not too long. I watched probably four different YouTube videos on this before I felt confident, and I still did a practice run on a scrap piece of coax first. My first attempt was okay but the solder on the center pin wasn't quite right so I redid it. The second one came out clean.

I ran the whole 100 feet as a single unbroken piece, which was the whole point. No barrel connectors, no splices, nothing. Zip-tied it along the fence with UV-resistant ties at about 18-inch intervals and gave it a drip loop before it enters the feedthrough. Then wrapped both ends — the connector at the antenna feedpoint and the connector at the feedthrough — with self-amalgamating tape. That stuff is genuinely great. It fuses to itself and makes a completely waterproof seal. I've had regular electrical tape fail on outdoor connectors before, so I don't mess around anymore.

The Results Were Actually Kind of Exciting

First thing I did after hooking everything up was run through the bands with an antenna analyzer. SWR curves looked essentially the same as before, which was expected — the antenna didn't change. But then I got on 20m and started listening around. I noticed the noise floor seemed slightly better, which could be placebo, could be real. Hard to quantify on receive.

On transmit though, I got a few signal reports within an hour of getting back on the air and three out of four of those contacts mentioned my signal was solid. One guy in Colorado said I was "full quieting" which was really satisfying to hear because he's someone I've worked before and I know he gives honest reports. I can't say with scientific certainty exactly how many dB I recovered by fixing the feed line, but the line loss difference between beat-up RG-8X with a bad connector versus clean LMR-400 over 100 feet is probably somewhere around 1.5 to 2 dB at 14 MHz. Not earth-shattering, but real.

What I'd Do Differently

If I'm being honest, I'd have bought good coax from day one. I know LMR-400 is pricier but over a 100-foot run to an HF antenna it's worth it. The price per foot sounds scary but you're not doing this every year if you do it right the first time. I'd also invest in a proper coax seal product earlier rather than hoping electrical tape would hold up.

One other thing — I'm going to start keeping a short log of my coax runs, what type, when installed, connector type at each end, and any weatherproofing applied. Nothing fancy, just a notepad file. That way if I'm troubleshooting in two years I don't have to try to remember whether that outdoor connector was properly sealed or not.

Anyway, if you've got a gnarly feed line situation you've been ignoring, take this as your sign to deal with it. It's not glamorous work and there's no big dramatic moment like hoisting up a new antenna, but a clean feed line is kind of the foundation everything else depends on. My 40m dipole and the 20m vertical both deserve better than what I was feeding them through, and now they've got it.

Next project is probably going to be proper grounding and bonding at the station entry point. I've got a ground rod but the bonding between it and the shack panel is not great. That'll be its own adventure.