It was a Tuesday in September 2022. I was three hours into a drive to a new DAS install site in suburban Atlanta, feeling pretty good about myself. I had my trusty Anritsu MS2721B spectrum analyzer in the back seat, a fresh calibration kit, and a project folder thick with schematics I'd personally reviewed. I'd been doing RF field testing for six years by then—I was not a beginner. Or so I thought.
When I pulled up, the site manager waved me over. "You're the PIM guy?" he asked. I nodded. "We've been live for two days. Upper band is shot. Customer's screaming."
I lugged my gear into the head-end room, fired up the Anritsu MW82119B PIM Master, and started scanning. Within five minutes I knew we were in trouble. PIM readings were hitting -95 dBm on a system that was spec'd for -150. And I knew, with a sinking feeling, exactly why.
I'd skipped the PIM pre-test.
Here's what happened.
The job was a mid-size DAS deployment for a 4-story office building. About 40 antennas, seven remote units, three floors of leased space for a major insurance company (I'll call them "Client C" since I can't use real names). The install crew had finished the day before I arrived. My job was to do the final system verification—sweep the cables, check the antennas, run a PIM test on each run, then hand off to the carrier.
But here's where I made my first mistake.
The crew lead, a guy I'd worked with for years, told me the install went "textbook." He'd personally inspected every connector. All the torque values were logged. The cable routing was clean, no sharp bends. I had a meeting in two days, so I figured: why not sweep the main runs first, then do a spot-check on PIM? Save time. The crew's good. It'll be fine.
Spoiler: it was not fine.
I started with the MS2721B to sweep the main feeders. All good. Insertion loss was within spec on every run. VSWR was clean. I went home that night feeling like a hero—until the phone rang the next morning.
The PIM test I'd planned to do as a "quick check"? I put it off. Then the next day the crew started terminating the last few antennas, and I figured I'd catch them at the end. Then I got pulled into a conference call about another site. Then the customer's carrier rep showed up early for the handoff.
You can guess how this pattern ends.
By the time I actually ran the PIM Master, we were already live. The carrier had turned up the radios two days earlier. And the PIM was so bad on the upper band that the customer's users were dropping calls in the elevator lobby. The facility manager sent an email with the subject line: "Intermittent Service in Conference Room 3B." He was being polite—but the carrier wasn't.
I ran a full PIM sweep on every port. Out of 44 runs, 12 had PIM levels above -130 dBm. Three were above -110. On one run—the one feeding the executive floor—the PIM hit -97 at 1900 MHz. That's basically an interferer.
Total non-compliant runs: 12 out of 44.
The repair process was brutal. I spent the next three days—three full days—re-terminating every suspect connector, re-torquing every jumper, and re-sweeping. Two runs needed new cable sections entirely. We found a crushed jumper under a ceiling tile (probably a dropped tool incident) and a connector that had been cross-threaded. The crew lead was mortified. I was just exhausted.
By the time we finally hit -155 dBm on every port, the customer had already filed a complaint with the carrier. The project's completion bonus? Gone. The carrier's account manager threatened to blacklist our company. I spent a week writing a root-cause report that basically said: "We didn't test PIM early. Period."
The final cost: roughly $4,200 in overtime for the rework, $2,800 in replacement materials (cable, connectors), and—the big one—a $5,000 penalty from the carrier for failing the acceptance test. Plus a reputation hit that took us six months to recover from. All because I skipped a step I knew was important.
Here's what I tell every engineer who joins our team now:
PIM is not something you can "spot-check." It's something you verify on every single run, before the system goes live. Even if the crew is perfect. Even if the cable looks clean. Even if you're in a hurry. PIM testing is the difference between a handoff and a catastrophe.
The Anritsu MW82119B PIM Master is not a "nice to have." It's the tool you use to prevent that email from Client C. The MS2721B spectrum analyzer will tell you if the signal is there—but the PIM Master tells you if the signal is clean. And in 2025 wireless, "clean enough" isn't enough. Carriers are demanding -150 dBc or better, and they will hold you to it.
(Note to self: I should write that root-cause report into a checklist. I still haven't done that. Maybe next quarter.)
After that disaster, I built a simple pre-install PIM testing protocol. It's not fancy. It's just six steps we follow before the carrier shows up:
Since we implemented this, we've completed 15 DAS deployments without a single PIM rejection. That's 15 sites, roughly 640 antennas, and zero customer complaints about interference. The up-front time cost is about 20 minutes per run—and the back-end savings? Priceless.
I still kick myself for that 2022 failure. If I'd simply followed this checklist—which I knew existed in my head—I'd have saved $12,000 and a week of misery. But at least now I can point to it and say: "This is what happens when you skip PIM testing. Don't be me."
The insurance company on that 2022 job? They switched carriers the next year. Not because of the coverage—the DAS was fine once we fixed the PIM. But because the initial experience "felt amateurish." A client doesn't know what PIM is. They just know their calls drop in the conference room. That perception sticks.
When I switched from "spot-checking" to "full PIM verification on every run," our client feedback scores improved noticeably. On one recent project, the network manager told us: "You're the first vendor whose PIM readings were actually signed off. It makes me trust your work." That trust is worth far more than the cost of a few extra connector swaps.
The MS2721B spectrum analyzer is great for signal-level troubleshooting. But for network reliability? The PIM Master is the real insurance policy. I learned that the hard way—so you don't have to.