Shielding Vent Window

Picking a Shielding Vent Window by Frequency – Get This Wrong and It Won't Shield

If you're buying a shielding vent window, the most important thing isn't the price. It's the frequency you need to stop.

Pick the wrong cell size, and that vent will look nice but do nothing. RF just sails through.

Here's how to match the vent to your frequency – without choking your fans.

The Short Version

The smaller the holes, the higher the frequency they block.

Quarter‑inch holes for low stuff. 1/16‑inch holes for 5G and radar.

But small holes kill airflow. So you want the biggest holes that still block your problem. Not the smallest you can find.

What Works for What Frequency

We test this stuff on our bench. Here's the rough map.

Quarter‑inch cells (about 6 mm)

Cutoff around 600 MHz. Good for stuff above that, but shielding isn't super high. Open area around 90% – air flows great. Use this for industrial controls, low‑frequency noise, older radios.

1/8‑inch cells (about 3 mm)

Cutoff around 1.5 GHz. Works from there up to maybe 6 GHz, but shielding drops as frequency goes up. Open area about 85% – still good airflow. Use this for most telecom, 4G, Wi‑Fi (2.4 and 5 GHz), military comms.

1/16‑inch cells (about 1.6 mm)

Cutoff around 3 GHz. Good from 3 GHz up to maybe 15 GHz. Open area drops to 75-80% – airflow starts to hurt. Use for 5G, radar, satellite, microwave links.

1/32‑inch cells (about 0.8 mm)

Cutoff around 6 GHz. Works up to 30 GHz and beyond. Open area maybe 60-70% – serious airflow restriction. Use for millimeter wave stuff.

How to Choose

First, figure out your worst frequency. The highest one you need to block. Not the average. The real one.

Then pick a cell size where that frequency is above the cutoff. Example – your problem is at 2.4 GHz. 1/8‑inch cells cutoff at 1.5 GHz, so you're above cutoff. Works fine. You don't need 1/16‑inch.

If your frequency is close to the cutoff – say 1.8 GHz on a 1/8‑inch vent – it'll shield, but not as well as at 2.5 GHz. So if you're near the edge, go one size smaller.

Also depth matters. A deeper vent (1 inch instead of 1/2 inch) shields better at the same cell size. But depth kills airflow too.

What People Screw Up

Biggest mistake? Buying the smallest cells they can find "just to be safe." Then their fans scream. If you don't need 1/16‑inch, don't buy it.

Another one – ignoring the low end. A vent that works at 2 GHz might leak at 500 MHz. But if you don't have a 500 MHz problem, who cares? Match the vent to your actual frequencies.

Also, not all 1/8‑inch vents are the same. Depth matters. A 1/2‑inch deep vent is fine. A 1/4‑inch deep vent shields way less. Ask for depth.

Real Examples

A 4G base station at 1.9 GHz. That's above 1.5 GHz, so 1/8‑inch cells work fine. Customer bought 1/8‑inch, 1/2‑inch deep. Shielding was 50 dB. Airflow was fine. Saved money by not going smaller.

A 5G small cell at 3.8 GHz. 1/8‑inch still works, but shielding is lower. They needed 60 dB. We recommended 1/16‑inch cells, 1/2‑inch deep. Got 60 dB. Airflow dropped a bit, but they had fan margin.

A radar at 9 GHz. 1/8‑inch gives maybe 20-25 dB – not enough. Used 1/16‑inch cells, 1‑inch deep. Got 55 dB. Airflow suffered – had to add a second vent. But it worked.

Low Frequencies?

Below about 300 MHz, waveguide vents don't help much. Cutoff is too low. For low frequencies, you need ferrite, conductive paint, or solid metal. But if your problem is above 300 MHz, waveguide vents are fine.

Depth Again

Worth repeating. A 1/2‑inch deep vent shields less than a 1‑inch deep vent of the same cell size. At 5 GHz, a 1/8‑inch cell, 1/2‑inch deep vent might be 35 dB. Same vent at 1‑inch depth might be 55 dB.

So if you're near the edge on frequency, go deeper. But pressure drop roughly doubles.

Test One First

Our numbers come from our lab. Your cabinet might be different.

If you're not sure, buy one sample. Test it at your frequency. Measure shielding with a spectrum analyzer. Measure pressure drop with a manometer.

Then order the rest.

Picking a shielding vent window by working frequency is easy once you know the rough map.

Quarter‑inch for low freqs, good air.

1/8‑inch for most telecom and Wi‑Fi.

1/16‑inch for 5G and radar.

1/32‑inch for millimeter wave.

Pick the biggest cell that still blocks your frequency. Don't overspec. Don't underspec. And don't forget depth.

We make all these. Tell us your frequency. We'll tell you what vent to buy. No upsell. Just what works. That's what we do.