The Frequency That Broadcasts Nothing — For Exactly 47 Seconds, Every Third Night

23:17 local time, October 15th, 2026

Six weeks ago, I was scanning the upper HF band — routine monitoring, nothing special — when I caught a carrier wave at 17.847 MHz. Clean signal, strong, no modulation. It lasted exactly 47 seconds, then cut off mid-transmission.

I logged it. Probably military, I thought. Frequency hopping test. Equipment malfunction. The usual explanations.

Then it happened again. Same frequency. Same duration. Two nights later.

THE PATTERN

I've documented 14 occurrences now. The signal appears:

• Every third night, without fail
• Always at 23:17 local time (± 3 seconds)
• Duration: 47 seconds (± 1 second)
• Frequency: 17.847 MHz
• Signal strength: S9+20dB (extremely strong for this band)
• Direction: Bearing approximately 340° from my location

No voice. No data. No morse. Just pure carrier wave — like someone keying up a transmitter and holding it open, broadcasting nothing.

WHAT I'VE RULED OUT

I've been tracking this for 7 years now, and I know the difference between anomalous and explicable:

• Not a numbers station (no modulation)
• Not frequency hopping (stays locked on same freq)
• Not propagation artifact (signal characteristics too consistent)
• Not my equipment (verified with backup SDR, different antenna)
• Not local interference (directional antenna confirms bearing)

I've cross-referenced with:

• Military exercise schedules: Nothing matches the pattern
• Satellite passes: No correlation
• Ionospheric conditions: Signal appears regardless of propagation quality
• Local infrastructure: No equipment cycling on this schedule

LAST NIGHT'S OBSERVATION

The signal appeared on schedule. But this time, I was ready with the directional beam antenna pointed at the bearing. Signal peaked exactly where previous measurements indicated — somewhere northwest of my position, probably 15-30 miles out.

That puts it in the national forest. No towers. No facilities I know of. Just ridge lines and hollow.

I hiked out there two days ago. Found nothing. No antenna, no equipment, no access roads that would support installation or maintenance.

THE ALTERNATIVE

Here's what keeps me honest: HF radio does strange things. Atmospheric ducting can make signals appear to come from directions they don't. Ground wave propagation can fool directional antennas. The signal could be originating hundreds of miles away and bouncing off the ionosphere at just the right angle to seem local.

And the timing? Could be automated equipment somewhere, cycling through diagnostic routines. The 47-second duration might mean something to an engineer familiar with the system. The three-day interval might align with maintenance schedules I'm not aware of.

I could be tracking a perfectly mundane radio beacon with a purpose I simply don't understand.

But.

THE NUMBERS DON'T LIE

Frequency: 17.847 MHz. There's that 17 again. Duration: 47 seconds. The counter-number. Interval: Every third night.

Coincidence has a pattern if you look long enough.

The signal is scheduled to appear again tonight at 23:17. I'll be listening. I've been searching for definitive proof for years — this isn't it. But it's another piece that doesn't quite fit the mundane explanations, and doesn't quite prove the alternative either.

Another entry for the log.

Have you monitored HF frequencies in your area and found recurring unexplained transmissions? Does anyone recognize this frequency as assigned to known operations?

Stay vigilant.

— JohnD_TN