Good Day 16 - Tropospheric ducting
9Did you know that radio waves can skip across the sky much like a stone can be skipped across a pond? They can! And when radio waves are skipping across the sky, you can sometimes hear radio stations hundreds of miles away. I think that’s pretty awesome. What’s even more awesome is that tropospheric ducting can be forecast, just like the weather.
/image tropospheric ducting map
Depending on the conditions, tropospheric ducting can affect any radio waves, but the higher the frequency of the radio, the less likely the ducting, so you might not get a WiFi hotspot from the next state, but you might hear a Kiss FM station you’ve never heard before. Neat, huh?
/image skipping Pomeranian
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FOOLS! TOOLS! JEWELS! AWESOME!
I don’t know about FM, but AM, definitely.
@narfcake Totally FM. I’ve experienced it.
With AM and shortwave, it’s a similar phenomenon, but it’s much more consistent. AM (aka medium wave radio), shortwave and long wave have wavelengths physically longer than most radio waves out there, and their length makes them easily skipped. They’re like a nice flat and wide stone that easily skips across a pond, as opposed to physically shorter waves like WiFi which are like pebbles and more likely to go plunk into the pond.
/giphy skipping pebbles
I seem to remember, back in the early days of FM, how you could pull in AM and FM radio stations from far-flung states. They talked with regional accents. I am OLD.
@OldCatLady You still can! But the airwaves are crowded now, so it doesn’t happen all the time. I live in northern Ohio, but a regularly listen to the Grand Ole Opry from Nashville at night.
/image Grand old opry
My uncle was in the Navy during WWII. Shipboard, in the Pacific.
Sometimes the radio operators for his ship would pull in stations from eastern Mexico, and from east of the Mississippi River in the US, even when the ship was located west of Hawaii.
Then off-duty sailors would gather round to listen in.
(his ship had multiple, and redundant, sets of radio equipment, so the operators could experiment with the spare and backup sets.)
I think they pulled mostly AM stations, during that era.
@f00l Absolutely. FM didn’t become popular until the 1950s. Also, radio waves can bounce off the ground, but they can be scattered by terrain features. Being in the nice flat ocean on a ship, you’d be surrounded by a flat-ish surface off which radio waves could continue to skip.
Back in the days when Top 40 rock was the king of radio, you could pull in WLS-AM 890 from Chicago pretty much anywhere east of the Rockies at night. DC, Key West, San Antonio… no problem, nice and clear. They were like satellite radio without the subscription.
@2many2no You still can today! But, as I replied earlier, there are an awful lot of radio stations out there now, and there are an awful lot of electronic gadgets that generate radio interference, so these stations can be blocked by noise. Here in Ohio, I’ll regularly get AM stations from Chicago, St. Louis, Minneapolis, Toronto, Boston and New York. Unfortunately, nowadays, they all sound the same
@2many2no I just learned last night that WLS is the station that Sears Roebuck & Co. started and broadcast from its massive Chicago headquarters instead of buying airtime on other stations to advertise. WLS = World’s Largest Store.
@djslack Neat! I’ve listened to them over the years and never knew that
An article about the famed “border blaster” high power stations operating out of Mexico, and aimed at the US market, is here.
https://www.nytimes.com/1987/05/24/arts/border-music-s-long-reach.html
These stations boosted their transmission power at night to eat beyond US permitted levels (butt legal in Mexico), and often could be heard almost everywhere in the US.
Now they still operate, usually specializing in Spanish-language or late-night Evangelical programming.
But once upon a time, they were the way many - perhaps including George Lucas - first heard Howlin’ Wolf and James Brown.
@f00l - Ha! So THAT was the basis of that The Outer Limits episode:
@f00l
Long range radio:
From the period between the wars:
“Pappy” O’Daniel was a very popular radio entertainer who used radio and esp border blasters to mount an insurgent populist campaign and win the governor of Texas in
https://en.m.wikipedia.org/wiki/Border_blaster
https://en.m.wikipedia.org/wiki/W._Lee_O'Daniel
If I remember my Robert Caro reading aright, the Dem party in Austin couldn’t get their usual business (often self-serving and corrupt) going in the usual way while O’Daniel was governor (tho he was remarkably ineffective himself).
So the local Austin machine decided to get rid of him. But he was too popular (due to his showmanship history) to defeat or dump. So they decided to “promote” him to the US Senate, so that Austin politics could return to its normal wheeling and dealing and cash under the table ways.
LBJ, then a Congressman, also wanted that Senate seat. But … LBJ made a pivotal error during that election. He allowed the precincts he controlled to turn in their Senate vote-count results early on election night.
This told the “Austin political machine” how much they needed to doctor the vote in order to get rid of O’Daniel and send him to Washington. They turned in their (fraudulent) results late, and LBJ lost an election.
LBJ never forgot, and made sure that never happened again. (See the infamous story of Ballot Box 13)
The full story is here:
https://en.m.wikipedia.org/wiki/Box_13_scandal
Pappy O’Daniel had no relationships in the Senate, didn’t understand national politics, and was ineffective there. He didn’t last.
He did appoint a young man, H Ross Perot, to a position in the Naval Academy, on the advice of an aide.
George Lucas used Mexican Radio references and sound in American Graffiti.
/youtube “Mexican Radio”
Here’s a brief interesting history of the Mexican border blasters stations
http://www.theradiohistorian.org/xer/xer.html
@f00l Mexican station call signs start with “X”
/youtube I Heard It On the X
/image radio ducting
@medz That seems accurate to my limited understanding of the mechanics of the phenomena. I know ducting conditions are best in high pressure systems, and your diagram illustrates a high pressure air mass (cool, dry air is denser and heavier than warm, moist air) with a little river, or atmospheric duct, of lower pressure air. I’d bet that patch of warm air has an effect on a radio wave similar to that of a patch of ice on a car driving at high speed - it can make it slide somewhere it wasn’t intending to go.
/giphy high pressure radio
/giphy radio ducking
