Border Blasters

[Chesterton]

This may or may not be a science question, I don't know. Yesterday I heard the ZZ Top song "I Heard It On The X", and was reminded of how, when I was a kid, we could pick up a Mexican radio station, but only after sunset.

I found the Wiki article on "border blasters", and it mentions stations that broadcast different wattages at day and night. For example,

"To improve reception of the station within its target market, KRPI applied and received an FCC construction permit [6] to increase its nighttime power from 10 to 50 kilowatts, change the community it served and move its transmitter from Ferndale to Point Roberts, a community adjacent to the Canada–US border."​

So if you want to improve reception, or reach a larger audience, why wouldn't you also want to do so during the daytime?

 

[AlexB23]

This may or may not be a science question, I don't know. Yesterday I heard the ZZ Top song "I Heard It On The X", and was reminded of how, when I was a kid, we could pick up a Mexican radio station, but only after sunset.

I found the Wiki article on "border blasters", and it mentions stations that broadcast different wattages at day and night. For example,

"To improve reception of the station within its target market, KRPI applied and received an FCC construction permit [6] to increase its nighttime power from 10 to 50 kilowatts, change the community it served and move its transmitter from Ferndale to Point Roberts, a community adjacent to the Canada–US border."​

So if you want to improve reception, or reach a larger audience, why wouldn't you also want to do so during the daytime?

Well, most AM stations actually reduce power at night, as the upper atmosphere reflects signals better at night, so the station does not need to use as much energy. So, why would a station want to increase nighttime power?

From the FCC (reducing power at night): Why AM Stations Must Reduce Power, Change Operations, or Cease Broadcasting at Night

Most AM radio stations are required by the FCC's rules to reduce their power or cease operating at night in order to avoid interference to other AM stations. FCC rules governing the daytime and nighttime operation of AM radio stations are a consequence of the laws of physics. Because of the way in which the relatively long wavelengths (see Footnote 1) of AM radio signals interact with the ionized layers of the ionosphere miles above the earth's surface, the propagation of AM radio waves changes drastically from daytime to nighttime. This change in AM radio propagation occurs at sunset due to radical shifts in the ionospheric layers, which persist throughout the night. During daytime hours when ionospheric reflection does not occur to any great degree, AM signals travel principally by conduction over the surface of the earth. This is known as "groundwave" propagation. Useful daytime AM service is generally limited to a radius of no more than about 100 miles (162 km), even for the most powerful stations.

 

[AlexB23]

By the way, for those not familiar with the "watt", a 50 kilowatt broadcast tower is around 50 times more powerful compared to a microwave oven, which operates at around 1 kilowatt (or 1000 watts).

 

[Chesterton]

Well, most AM stations actually reduce power at night, as the upper atmosphere reflects signals better at night, so the station does not need to use as much energy. So, why would a station want to increase nighttime power?

From the FCC (reducing power at night): Why AM Stations Must Reduce Power, Change Operations, or Cease Broadcasting at Night

Most AM radio stations are required by the FCC's rules to reduce their power or cease operating at night in order to avoid interference to other AM stations. FCC rules governing the daytime and nighttime operation of AM radio stations are a consequence of the laws of physics. Because of the way in which the relatively long wavelengths (see Footnote 1) of AM radio signals interact with the ionized layers of the ionosphere miles above the earth's surface, the propagation of AM radio waves changes drastically from daytime to nighttime. This change in AM radio propagation occurs at sunset due to radical shifts in the ionospheric layers, which persist throughout the night. During daytime hours when ionospheric reflection does not occur to any great degree, AM signals travel principally by conduction over the surface of the earth. This is known as "groundwave" propagation. Useful daytime AM service is generally limited to a radius of no more than about 100 miles (162 km), even for the most powerful stations.

Thank you! I feel vindicated in my mind. When I first wondered why we could only hear the X at night, I wondered if it had something to do with the physics of atmospheric conditions. But while researching I came across that Wiki bit about stations intentionally increasing power at night. So I thought maybe it's just a business decision, and people will think I'm an idiot if I think it has something to do with science. That's interesting.

 

[Chesterton]

 

[AlexB23]

Thank you! I feel vindicated in my mind. When I first wondered why we could only hear the X at night, I wondered if it had something to do with the physics of atmospheric conditions. But while researching I came across that Wiki bit about stations intentionally increasing power at night. So I thought maybe it's just a business decision, and people will think I'm an idiot if I think it has something to do with science. That's interesting.

You are welcome. It is probably a business decision, to get as much range as possible. In fact, the power should be cranked during the day, to keep the range.

 

[AlexB23]

Ooh, a classic. I love 1970s music.

 

[AV1611VET]

When I was in radiocommunications in the Navy (RMA school in San Diego), I learned that radio stations can transmit to other radio stations from tower to tower.

This is known as "line of sight" transmitting.

You can transmit further -- (such as over the horizon) -- by bouncing your signal off of the ionosphere.

The ionosphere, during the day, is pretty solid, due to receiving energy from the sun.

But at night, when the sun goes down, the ionosphere thins out.

As it thins out, the transmitted signal goes farther out, due to the angle of refraction getting larger.

So your intended station can no longer receive your signal, but a station farther away can.

This is known as "skip distance."

Boosting the signal at night will result in the signal being lost into space as it penetrates the thinner ionosphere.

 

[AlexB23]

When I was in radiocommunications in the Navy (RMA school in San Diego), I learned that radio stations can transmit to other radio stations from tower to tower.

This is known as "line of sight" transmitting.

You can transmit further -- (such as over the horizon) -- by bouncing your signal off of the ionosphere.

The ionosphere, during the day, is pretty solid, due to receiving energy from the sun.

But at night, when the sun goes down, the ionosphere thins out.

As it thins out, the transmitted signal goes farther out, due to the angle of refraction getting larger.

So your intended station can no longer receive your signal, but a station farther away can.

This is known as "skip distance."

Boosting the signal at night will result in the signal being lost into space as it penetrates the thinner ionosphere.

This is true. Here is a visual of the skip distance.

 

[Chesterton]

You are welcome. It is probably a business decision, to get as much range as possible. In fact, the power should be cranked during the day, to keep the range.

What I also learned is that unlike in the U.S., until the '70's, the Mexican government had no regulations about the watts their radio stations could use, so back in the day, Mexican stations, if they wanted, could have out-signaled many radio stations of the southern U.S., day or night.

 

[AlexB23]

What I also learned is that unlike in the U.S., until the '70's, the Mexican government had no regulations about the watts their radio stations could use, so back in the day, Mexican stations, if they wanted, could have out-signaled many radio stations of the southern U.S., day or night.

That is interesting. At least the Mexican stations got wattage regulations in the 1970s. Out-signalling is a little unethical, regardless of nationality the station is located in.

 

[BCP1928]

Not a word about Wolf Man Jack?

 

[AV1611VET]

This is true. Here is a visual of the skip distance.

 

[AV1611VET]

The pilot episode of the Outer Limits deals with radio wattage.

The Galaxy Being

 

[AlexB23]

Hey, thanks. I love scientific graphics.

 

[AlexB23]

The pilot episode of the Outer Limits deals with radio wattage.

View attachment 348683

The Galaxy Being

I might have watched the 1990s version of the Outer Limits, or a few episodes of it (including S1E2: Valerie 23). I have got to watch the original one. This was the Black Mirror of the 1960s. I have not watched Black Mirror either.

 

[Chesterton]

Not a word about Wolf Man Jack?

Ha ha, yeah there are actually a lot of pop culture references to border blasting.

 

[AlexB23]

Ha ha, yeah there are actually a lot of pop culture references to border blasting.

Wow, I have never known that border blasting had references back then in the 1980s.

 

[The Liturgist]

By the way, for those not familiar with the "watt", a 50 kilowatt broadcast tower is around 50 times more powerful compared to a microwave oven, which operates at around 1 kilowatt (or 1000 watts).

Indeed. It’s a fantastically bad idea to stand in front of an RF or microwave transmitter.

 

[BCP1928]

Wow, I have never known that border blasting had references back then in the 1980s.

All the way back to the '80s. Wow. I used to listen to them all the way back to the 50s--before the Wolf Man.