Passive intermodulation is the quiet killer of network performance. The site “works,” every light is green — and users still get half the throughput they should. Here’s what PIM is and how we hunt it.
What PIM actually is
When two or more strong transmit signals meet a passive nonlinearity — a loose connector, a corroded mount, a rusty bolt in the beam path — they mix and generate new frequencies. Some land squarely in the receive band, raising the noise floor. The radio hears its own site shouting over the users. Sensitivity drops, cell edge shrinks, throughput falls.
5G makes it worse: more bands on the same steel, higher power, and mid-band carriers whose intermod products land in more receive windows.
How we hunt it
PIM testing with two high-power carriers and a spec threshold, not a feeling.
- Torque-check every connector in the path — most PIM is a wrench problem.
- Swap suspect jumpers before condemning expensive components.
- Inspect mounts and nearby steel; external PIM is real and often ignored.
- Document before/after readings so the fix is proven, not assumed.
Design it out first
The cheapest PIM fix happens on paper: PIM-rated components, transmit paths kept off rusty steel, proper weatherproofing at every junction. That’s why PIM mitigation is part of our Design & Planning service — a site revisit costs ten times what prevention does.