Megahertz to Millihertz
MHz
mHz
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
1 MHz (Megahertz) → 1000000000 mHz (Millihertz) Just now |
Quick Reference Table (Megahertz to Millihertz)
| Megahertz (MHz) | Millihertz (mHz) |
|---|---|
| 87.5 | 87,500,000,000 |
| 100 | 100,000,000,000 |
| 108 | 108,000,000,000 |
| 433 | 433,000,000,000 |
| 900 | 900,000,000,000 |
| 1,000 | 1,000,000,000,000 |
| 2,400 | 2,400,000,000,000 |
About Megahertz (MHz)
A megahertz (MHz) equals one million hertz and covers FM radio, VHF/UHF television, and older CPU clock speeds. FM radio in most countries is allocated the 87.5–108 MHz band. Early home computers and microprocessors ran at 1–20 MHz; the original IBM PC used an 8088 at 4.77 MHz. Wi-Fi channels in the 2.4 GHz band have bandwidths of 20 or 40 MHz. Wireless standards including Bluetooth, Zigbee, and many cellular bands also operate in the low hundreds of megahertz up to a few gigahertz.
FM radio broadcasts between 87.5 and 108 MHz. The original IBM PC ran at 4.77 MHz. Many smartphone processors boost to over 3,000 MHz (3 GHz).
About Millihertz (mHz)
A millihertz (mHz) is one thousandth of a hertz, corresponding to periods of minutes to hours. Millihertz frequencies appear in oceanography (tidal oscillations, slow wave action), geophysics (free oscillations of the Earth after major earthquakes), and physiology (very slow biological rhythms). The Earth's fundamental free oscillation modes — the lowest-frequency seismic normal modes — ring at a few millihertz in the aftermath of great earthquakes. Infrasound below 20 Hz also has a millihertz region for its slowest components.
Earth's gravest free oscillation mode rings at about 0.3 mHz (period ~54 minutes) after large earthquakes. A 1 mHz signal completes one cycle every 16.7 minutes.
Megahertz – Frequently Asked Questions
Why did the original IBM PC run at the oddly specific speed of 4.77 MHz?
IBM needed a clock that could derive both the CPU timing and the NTSC color-burst frequency (3.579545 MHz) for the built-in composite video output. Multiplying the color-burst frequency by 4/3 gave 4.77 MHz — a convenient compromise that let one crystal oscillator serve two purposes. The weird number was pure engineering pragmatism, not performance targeting.
What is the 433 MHz band and why do so many gadgets use it?
The 433.05–434.79 MHz range is an ISM (Industrial, Scientific, Medical) band that is license-free in most of Europe. Cheap remote-control key fobs, weather stations, garage door openers, and IoT sensors all crowd into it because you can legally transmit at low power without a radio license. In the US, the equivalent unlicensed band is 315 MHz, which is why European and American car key fobs are not interchangeable.
How does FM radio achieve better sound quality than AM at a higher MHz frequency?
AM encodes audio by varying the wave's amplitude, which is vulnerable to electrical interference (lightning, motors). FM varies the frequency instead, making it inherently noise-resistant. FM also has a wider channel bandwidth (200 kHz vs. AM's 10 kHz), allowing it to carry the full 20–15,000 Hz audio spectrum in stereo. The MHz carrier frequency itself isn't what improves quality — it's the modulation method and bandwidth.
What happened to the megahertz race in CPUs during the early 2000s?
Intel and AMD marketed processors by clock speed — 500 MHz, 1 GHz, 2 GHz — implying faster was always better. By 2004, Intel's Pentium 4 hit 3.8 GHz but ran so hot and consumed so much power that performance-per-watt cratered. The industry pivoted to multi-core designs: instead of one core at 4 GHz, you got two or four cores at 2 GHz each, doing more total work with less heat. Raw megahertz stopped being a useful buying metric.
Why is Bluetooth limited to the 2,400 MHz band?
Bluetooth operates in the 2.4 GHz ISM band (2,400–2,483.5 MHz), which is reserved globally for unlicensed use. This avoids the need for regulatory approval in each country. The trade-off is sharing the band with Wi-Fi, microwaves, and baby monitors. Bluetooth mitigates interference by hopping between 79 channels 1,600 times per second — if one frequency is jammed, it has already moved on.
Millihertz – Frequently Asked Questions
What does Earth sound like when it rings at millihertz frequencies after an earthquake?
After a magnitude-9 earthquake the entire planet vibrates like a struck gong, with its deepest mode at about 0.3 mHz — one oscillation every 54 minutes. The surface rises and falls by fractions of a millimeter. You cannot hear it (human hearing starts at 20 Hz), but gravimeters and seismometers worldwide pick it up. The 2004 Sumatra quake kept Earth ringing measurably for weeks.
Why do ocean scientists care about millihertz frequencies?
Ocean swells, tidal constituents, and seiches (standing waves in harbours or lakes) all oscillate in the millihertz band. A 10-second ocean swell is 100 mHz; a harbour seiche with a 10-minute period is about 1.7 mHz. Monitoring these frequencies helps coastal engineers predict resonance in ports and design breakwaters that don't amplify destructive wave energy.
Can humans sense anything at millihertz frequencies?
Not directly — our senses are far too fast. But some physiological rhythms operate here: the Mayer wave, a ~0.1 Hz oscillation in blood pressure, sits at the high end of the millihertz scale, and slower vasomotion (tiny blood vessel contractions) can dip below 10 mHz. You don't feel them as vibrations, but they show up clearly on a continuous blood-pressure monitor.
What is infrasound and does it overlap with millihertz?
Infrasound is sound below the ~20 Hz threshold of human hearing. The lowest infrasound blends into the millihertz range — the International Monitoring System for nuclear-test detection listens down to about 20 mHz. Sources include volcanic eruptions, meteor airbursts, severe storms, and ocean microbaroms (standing pressure waves between ocean swells and the atmosphere).
How are millihertz signals detected if they are too slow to hear?
Instruments record a time series (pressure, acceleration, displacement) over hours or days, then apply a Fourier transform to extract frequency content. Superconducting gravimeters can resolve Earth's free oscillations below 1 mHz by measuring gravity changes of 10⁻¹² g. The trick is not a fast sensor but a patient, ultra-stable one and enough data to separate signal from drift.