If you’re managing a Distributed Antenna System (DAS) or planning an in-building mobile coverage solution in Australia, you’ve probably heard of Passive Intermodulation, or PIM. But what exactly is it? Why does it matter? And how do you test for it?
Let’s break it down.
What Is Passive Intermodulation (PIM)?
PIM is a form of RF interference that occurs when two or more radio signals mix in a non-linear environment, like a corroded connector, loose bolt, or even dissimilar metals touching. The result is the generation of unwanted “ghost” signals at new frequencies — often right in your network’s uplink band.
In simple terms:
PIM is the static that ruins a clean RF signal. You can’t see it, but your mobile coverage feels it — with dropped calls, poor voice quality, and slow data.
How PIM Affects DAS Systems
In Australian DAS installations — especially those in commercial offices, tunnels, hospitals, or stadiums — PIM is a leading cause of degraded network performance.
According to the MCF DAS Design Guidelines, PIM can affect DAS by:
- Raising the noise floor in the uplink path
- Reducing signal-to-noise ratios (SINR)
- Lowering capacity and data throughput
- Compromising coverage consistency
And it gets worse: even well-installed systems can develop PIM over time due to vibration, corrosion, or thermal cycling.
Common Causes of PIM
From both Kaelus and IWPC best practices, the main culprits behind PIM include:
- Loose or corroded RF connectors
- Metal flakes or dirt inside connectors
- Use of dissimilar or ferromagnetic metals
- Damaged coaxial cables or poorly prepared terminations
- Nearby metal structures (flashing, bolts, HVAC ducts)
Even a tiny metal burr or speck of corrosion near an antenna can generate significant intermodulation.
How Is PIM Tested?
PIM testing uses a dedicated analyser that injects two high-power RF tones into your DAS, then listens for the resulting 3rd-order intermodulation products. If those products fall within the receive band — it’s a problem.
Testing typically includes:
- Static PIM test: Measures system linearity at rest
- Dynamic PIM test: Introduces vibration (e.g. tapping connectors) to simulate real-world use
- Return loss check: Verifies the RF path is intact
- PIM vs. Time: Captures intermittent issues over time
At Digicom Wireless, we use Kaelus IPA Series analysers — reliable, carrier-grade tools trusted across Australia for precise PIM detection and certification.
What Are the Acceptable PIM Levels?
According to IWPC and MCF standards:
- New installations: Aim for PIM levels of –107 to –110 dBm
- Aged sites: Acceptable PIM may be around –97 dBm
- High PIM (> –90 dBm): Indicates serious problems
Even a 1 dB drop in uplink sensitivity due to PIM can reduce coverage by up to 11%, and increase call drops or data lags significantly.
Preventing and Resolving PIM
You can reduce the risk of PIM by:
- Using factory-certified low-PIM components
- Following proper cable preparation and torqueing procedures
- Performing PIM tests during commissioning
- Including PIM checks in routine maintenance
If issues are found, we can help re-terminate connectors, replace faulty cables, and re-test until the site meets performance criteria.
PIM Testing with Digicom Wireless
We provide full-service PIM testing across Australia, including:
- Onsite certification & fault finding
- Kaelus PIM analyser hire (short- or long-term)
- DAS health checks & remediation support
Whether you’re a building manager, DAS contractor, or RF consultant — we help ensure your system meets Australian carrier expectations and delivers clean, reliable in-building coverage.
We’re Here to Help
Book a PIM test or request an equipment hire quote today? Contact us and let our team of experts guide you every step of the way. Digicom Wireless can help you assess your current signal strength and design a tailored solution using Cel-Fi boosters or Distributed Antenna Systems (DAS).
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