The Frequency That Wasn't There: Surveillance or Signal Drift?

April 3rd, 2026 — 03:17 local time

I need to document this while the details are fresh, even though I'm not sure what I'm documenting.

Three nights ago, my software-defined radio setup started picking up something unusual. A narrow-band transmission on 162.450 MHz — right in the middle of the NOAA weather radio band, but offset from any legitimate channel. The signal was clean, periodic, lasting exactly 47 seconds every 17 minutes.

Yes, those numbers again.

The transmission itself was encrypted or encoded — my spectrum analyzer showed a consistent waveform pattern, but nothing I could decode with standard protocols. Not voice. Not standard digital modes. Just... structured noise with a rhythm to it.

The Pattern

• Night 1 (March 31): Signal detected 02:34-05:18, nine complete cycles • Night 2 (April 1): Signal detected 02:31-05:22, ten complete cycles • Night 3 (April 2): Signal detected 02:29-05:19, nine complete cycles

Each night, the signal started roughly 2-3 minutes earlier. Like something was drifting — either the transmission schedule or my equipment's reference clock. I checked my GPS-disciplined oscillator three times. It was solid.

I've been tracking this for 7 years now, and I've learned to separate equipment quirks from genuine anomalies. This felt like the latter.

Then the Surveyors Arrived

Yesterday morning, I drove into town for supplies. Coming back up Route 64, I passed two white Ford F-250s parked at Mile Marker 17. Government plates. Two men with surveying equipment on tripods, but they weren't looking at the ground — they were pointed at the ridge line. At my ridge line.

I didn't stop. I've learned that lesson.

Last night? No signal. Clean spectrum. Nothing on 162.450 MHz except the faint carrier from the legitimate NOAA station 30 miles north.

The Mundane Explanation

Here's what I keep coming back to: SDR equipment can produce false signals from intermodulation — when two strong frequencies mix in the receiver and create a phantom signal that was never really transmitted. The NOAA weather station is powerful. There's a commercial FM station 15 miles south. Under certain atmospheric conditions, these could combine in my receiver to create exactly what I observed.

The timing? Coincidence. The Surveyors show up seasonally to maintain telecom infrastructure. They weren't looking at my equipment — they were probably sighting for a new cell tower or checking existing installations.

The 47-second, 17-minute pattern? Human pattern recognition in random noise. I wanted to see those numbers, so I did.

That's the honest assessment. That's what my engineering training tells me.

But Here's What Doesn't Fit

The signal drift was consistent across three nights — earlier by 2-3 minutes each time. Intermodulation doesn't drift like that. It's either present or it isn't, based on propagation conditions.

I ran the numbers through my notebooks. The last time the Surveyors were at Mile Marker 17 was September 2025 — six months ago, almost to the day. The last time I logged unexplained VHF activity? September 14th, 2025. Three days before they showed up then, too.

I have seventeen documented instances over seven years where unusual signals ceased within 48 hours of surveyor activity in the area. Seventeen.

Coincidence has a pattern if you look long enough.

Another Entry for the Log

I'm not claiming proof of anything. The intermodulation theory is solid. The Surveyors are probably exactly what they appear to be — contractors maintaining infrastructure. Maybe I'm seeing patterns where there's just random correlation.

But I can't explain the consistency. And I can't shake the feeling that something stopped transmitting the moment someone knew I was listening.

The signal-to-noise ratio is getting worse — not in my equipment, but in my ability to separate genuine anomalies from self-deception. After all these years without definitive proof, maybe I'm just seeing what I want to see.

Or maybe that's exactly what they're counting on.

Stay vigilant.

— JohnD_TN