Is AM Radio VHF?

Very high frequency or VHF signals have a radio frequency range between 30 and 300 MHz.

Marine radio heavily relies upon this frequency, but what about AM radio? Is it considered VHF?

AM radio is not VHF, as the frequencies are too high. Instead, the AM broadcast band (at least in part) exists on medium frequencies or MF, which range from 300 kHz to 3 MHz.

Today’s article will explain why AM radio is not VHF and reveal which frequency range AM broadcasts exist on. Ham radio enthusiasts won’t want to miss it.

Is AM VHF?

AM broadcasts and VHF frequencies exist in the radio world, but they are not synonymous with one another.

In other words, AM radio is not VHF. Let’s explain why.

AM radio is a form of broadcasting that relies on amplitude modulation. We’ve talked about this form of transmission elsewhere on the blog, but let’s do a little recap here.

Amplitude modulation relies on radio waves to send a message electronically.

The signal strength or amplitude changes according to the audio signal. AM is the original radio broadcasting method in the early 20th century.

Although it’s been largely usurped by frequency modulation or FM, about 6,000 AM stations still exist in the 2020s, so AM hasn’t died.

AM doesn’t use VHF frequencies, though. You’ll recall that VHF radio waves exist on a radio frequency between 30 and 300 MHz.

VHF is close to the top of the frequency band range chart. Other frequencies exist above it, such as ultra high frequency or UHF (with a frequency range of 300 MHz to 3 GHz) and super high frequency or SHF (with a frequency range of 3 to 30 GHz).

However, for the sake of AM radio, we have to look at frequencies below VHF.

No, not high frequency (with a range of 3 to 30 MHz), but medium frequency or MF.

Medium frequency includes a frequency range of 300 kHz to 3 MHz.

What Is Medium Frequency?

Medium frequency is a huge step down from VHF, with only low and very low-frequency ranges below it.

This band is referred to as a hectometer band due to the range of the wavelengths, up to one hectometer.

A hectometer is the equivalent of 100 meters.

A radio wave in the MF wavelength comes from ground waves, which are adjacent and parallel to the earth’s surface and trace along the planet’s natural curvature.

The wavelengths reflect off the ionosphere and then diffract.

The diffraction process allows the radio waves to travel over obstacles like hills and trees.

However, taller structures such as mountain ranges can often stop the radio waves.

How Far Can MF Radio Waves Travel?

A radio station broadcasting on MF frequencies shares some of the AM band.

If you’ve read our recent posts on AM radio wave travel, it shouldn’t surprise you that MF radio waves can travel hundreds of miles.

Damper and wetter environments facilitate longer-distance travel because MF waves propagate from ground waves.

However, that’s not the only way MF radio waves can travel.

They can also use sky-wave propagation, a process recently discussed on the blog.

Sky-wave propagation occurs in the ionosphere, where the ions and molecules group up by night to increase the radio wave’s transmission distance even more.

The sun ionizes the particles by day in the E and F layers. The molecules refract the radio waves, which can be impeded by D layers, which absorb some MF radio waves.

When solar activity levels increase, this happens more readily.

It’s also a frequent occurrence by day versus at night, and interference is likelier in the summer when the sun is harsher and out for more hours.

MF radio waves propagate much more readily during other times of the year, making up for a spotty summer.

For instance, winter is when these radio waves travel the furthest. That’s also the case when solar activity decreases.

Instead of traveling hundreds of miles, MF radio waves can travel thousands of miles.

The F layer, which is much more prominent than the D layer of the ionosphere in these conditions, refracts the signal.

This has its benefits and its downsides.

One of the biggest perks is how MF waves can facilitate long-distance news and communication.

However, local stations might notice more interference.

Why does this happen? MF frequencies are usually spaced a few hundred miles apart on broadcasting stations since they share the same frequency.

However, in optimal conditions, the miles of distance between the frequencies don’t have the same effect.

Several stations can have their signals boosted by the ionosphere, interrupting other stations on that frequency band.

That’s why the FCC limits AM broadcasts by night, requiring some stations to shut down and others to reduce power.

The North American Regional Broadcasting Agreement, or NARBA, was created to settle this issue.

What Is Medium Frequency Used For?

Now that you understand where AM radio exists–in MF rather than VHF frequencies–let’s explore the uses of MF signals.

Maritime Communication

One of the most significant uses of MF frequencies is maritime communication.

Coastguards worldwide will communicate with their crews on the shore using frequencies from 1600 to 2850 kHz.

For example, the US Coast Guard operates on the MF frequency 2670 kHz, the Stornoway Coast Guard on the 1743 kHz frequency, and the French MRCC on either the 1696 or 2677 kHz frequency.

If maritime operations require a non-directional navigational radio beacon between 190 and 435 kHz, that includes part of the low frequency or LF range and the lowest MF range.

The MF frequency 2182 kHz is used for international distress and enables voice communications between sailors and their crew.

AM Radio Broadcasting

The MF frequency band is often employed for AM radio broadcasting, as radio stations use frequencies between 526.5 and 1605 kHz globally.

The frequency range in North America is 525 to 1705 kHz; in Europe, it’s 526.5 to 1606.5 kHz.

Amateur AM radio occupies a band at around 160 meters, but some stations use top-band MF frequencies from 1800 to 2000 kHz.

Conclusion

AM radio does not use VHF frequencies but MF frequencies instead.

The travel propensity of these radio waves enables them to expand hundreds to thousands of miles depending on the condition of the ionosphere.

Besides AM radio broadcasting, MF frequencies are trusted for maritime communications, including sending distress signals.