Look, I'm not a cybersecurity analyst, and I sure as heck am not a full-time network architect. My whole world is RF — specifically, making sure the spectrum is clean and the signals are behaving. So when a client called me up last March, 48 hours before a major product launch event, and said "figure out what is on my wifi causing our demo to crash," my first thought wasn't 'packet sniffing.' It was 'someone's got a noisy piece of gear or an overlapping channel.'
And that, right there, is the gut check of any field engineer with a Spectrum Master in the truck: the problem is almost never the protocol. It is the physical layer. The invisible neighbor stomping around on the party channel.
The client was a hardware startup. Their big demo involved a dozen IoT devices talking to a central tablet over 5 GHz WiFi. Two hours into rehearsals, the tablet kept losing connection. The event was in a hotel ballroom — a notoriously filthy RF environment. They tried swapping channels on their access point. No change. They rebooted everything (because that's always step one). No change.
That's when they called me. The exact ask: "Can you tell us what device or signal is stomping on our network? We need you to 'visualize' the interference." They didn't need a protocol analysis report. They needed a visual smoking gun.
I pulled out the Anritsu Spectrum Master MS2711E. The goal wasn't just to see a signal — it was to characterize it. Was it a continuous noise source? A chirping radar? A bursty communication protocol? You can't fix what you can't see.
I started with a standard 5 GHz sweep. And right there, sitting on top of one of the UNII-1 bands they were using, was this broad, ugly hump of noise. It wasn't a clean WiFi waveform. It looked like a sinusoid with some harmonic garbage. "That," I told the client's lead engineer, "is not a router. That's probably a leaky cable or a cheap amplifier."
"I knew I should have brought the directional antenna on site, but thought 'the omni will be fine.' Well, the omni caught the noise but couldn't pinpoint it. That was the moment I realized I needed to go back to the truck."
Skipped the proper site survey gear that morning because it 'never matters.' That was the one time it mattered. I had to run back to the field truck to grab the directional horn antenna. Classic field engineer mistake. Took 20 minutes I didn't have.
With the horn, I walked the room. Signal strength peaked at the back-left corner of the ballroom, behind a curtain. Stuffed behind a service panel? A portable air conditioning unit. Those things have variable speed motors and cheap power supplies. They bleed RF garbage like a sieve. The unit was sitting 15 feet from their demo station.
The surprise wasn't that something was interfering. It was what it was. The client was fixated on 'rogue routers' or 'spectrum jammers.' It was a $400 portable AC unit the event staff had placed there without telling anyone. The motor driver was dumping broadband noise right into the 5 GHz band.
We moved the AC unit 50 feet away into the hallway. The noise floor dropped by 15 dB. The tablet reconnected instantly. The demo ran perfectly for the next two days. The client's alternative was cancelling the launch event — a move that would have lost them their first major retail partner.
This is where my view on customer education kicks in. After the panic subsided, I sat down with their team. We talked about what they saw on the Anritsu screen. I showed them how a 'WiFi analyzer' on a laptop would have missed the AC unit's noise pattern because laptop software looks for protocols, not raw RF pollution.
They learned that 'what is on my wifi' is rarely a device that is 'on' your network. It's a device that is filling up the airspace your network lives in. An informed client asks better questions. Now, they call me for a site survey on every major event—and they check what's plugged in nearby.
Bottom line: If you're asking 'what is on my wifi,' don't just look at the DHCP table. Grab a spectrum analyzer. Walk the room. You'll be surprised what's hiding behind a curtain.