Most of us probably never think about listening for meteors on shorwave radio, but it certainly can be done. Back in the 1960s I used a very simple shortwave radio setup and a screen-wire antenna to do primitive forward-scattering reception of over-the-horizon radio stations from the plains of West Texas.

Last night a very bright and long-lasting fireball whizzed over eastern New Mexico and parts of the Texas Panhandle, and Tom Ashcraft captured it using his antenna array and RadioJove receiver. He put the results through his spectrogram software and created a broad-spectrum picture of the event, then matched his captured audio file to the video from an all-sky meteor patrol camera to create a movie which you can download here.

If you put that into an MP4 player that shows running time, listen to it using headphones. After you've heard it all the way through once or twice, adjust the volume until you can hear a slight hiss in the headphones and then play it again while watching the running time.

At between 1:27 and 1:28 you'll hear a bass thump, very distinct, short, sharp, with a slight echo. It reminds me of the footfalls of the Creature of the Id, from the sci-fi classic Forbidden Planet, in the scene where it stalks through the defense perimeter of the grounded spacecraft and up a flight of stairs.

I tell you, it raised the hair on the back of my neck (both in the movie and in Ashcraft's meteor recording).

I have no way to account for this low-frequency transient, if it's not something in the audio system itself, or an artifact of post-processing. It only happens that one time, however, so I suspect it's real.

Anyway, the file itself is an excellent demonstration of the phenomenon of radio reflection detection of meteors. Give a listen!

 Radio waves can be used to image any object, in this case though I think you are referring to passive radio detection as opposed to sending out radio energy (like radar) to image an object.

 I don't know to be honest. An object entering our atmosphere at high speed will create an ionized coccoon of plasma around it as the air becomes super heated from the friction. Plasmas are electrically charged and would probably generate radio waves.

 However an inert object in space like an asteroid or a comet would not be likely radio sources. Even if there was a weak signal from some natural phenomena it would likely be lost in the background noise.

That being said there are objects in our solar system which emit strong radio waves. You should google for recordings of Jupiter on ham radio sets. Talk about eerie sounds.

 

I know what you mean, as I operate a Radio Jove receiver and am relocating the antenna array to 3RF's Comanche Springs Astronomy Campus next summer.

Yes, the link I provided was to reflected radio waves. There are two ways to think about forward-scattering:

• You can pair up with another (distant) radio amateur and bounce signals between you using meteor ionization trails for reflectors.
• You can listen to a distant radio or TV signal using meteor trails.

In the case of the link I provided, Ashcraft was doing the second method. He recorded signals from two TV broadcast channels and several radio stations as the bolide ionized the atmosphere along its path.

You can do this yourself using a simple FM radio receiver and a good whip antenna, during meteor showers. Since you're in McKinney, a good way to try this would be to tune in on Oklahoma stations during the Perseids in August. The basics of the method are simple:

• Check the location of the shower radiant from your site during the hours just before, during, and after the peak of the shower.
• Locate several over-the-horizon radio stations which you can't hear, or can barely hear, under normal conditions. Look for stations along, or to 30 degrees either side of, a line between your site and radiant of the shower.
• Good distances are between 50 and 100 miles (or a bit further if the stations are high-wattage broadcasts).
• Select stations whose frequencies do not correlate with nearby, stronger signals.
• During the hours just before, during, and after the shower peak, tune in the station. If you can hear it clearly, tune slightly to one side or the other of the frequency until it just drops out. If you can hear it intermittently, detune very slightly until it just drops out.
• I listen with headphones to mask background noise, but do not use noise-cancelling headphones as they can trap transients.
• While listening, watch the sky for meteors. What normally happens is that meteors which pass more or less directly between you and the distant station will bounce the signal to your receiver. This briefly increases the signal to your set and the station will suddenly become audible, or will come in more clearly.

The effects of such augmentation of signal last from seconds to a few minutes, depending on the size and intensity of the meteor trail(s).

With better equipment, such as that used by radio amateurs, you increase your chances of detection and likewise the length and strength of the effects. As a matter of fact, radio amateurs routinely use meteor trails to bounce their signals great distances. A simple World Band shortwave radio with an extendable whip or clothesline-reel antenna works quite well as a receiver.

 I never thought about that. Using a terrestrial radio source in that way is rather brilliant. I have a handy little Yaesu hand scanner. I wonder what a unidirectional antennae mounted to my scope would be like. It'd probably be too small to pick up Jupiter's signals and such.

Since you have it already, it won't hurt to try.

Tune to Jupiter between 20MHz and 21MHz. I pick it up on my Grundig portable quite often at 20.1Hz.

You want to use a dipole antenna cut to that frequency if you can. If your scanner has an antenna jack (or, more likely, a plug-in or screw-in stubby antenna), you can get the same connector at Radio Shack and make a dipole from plain copper antenna wire and a couple of insulators.

Here's a link to the single-dipole construction manual from the Radio Jove site. That site is a gold mine of info for anyone wanting to get a start in radio astronomy.

If you're going to go this route, you'll need an open space, free of other wires either overhead or underground, that's about 10 feet by 32 feet. You want the antenna to be high enough to give you a clear line of sight to Jupiter as it rises, and to walk under (no trip or head hazards).

If you don't have that kind of free space, you can make a simple quad antenna from loops of wire and a piece of PVC pipe. One advantage of a quad is that it is higher gain and easier to aim. A disadvantage is that you have to aim it(!), whereas a dipole just runs N/S and you pick up Jupiter along its length as the Earth's rotation brings it past the planet in the sky.

Here's a link to times of predicted Io storms for various time zones. Jupiter and Io interact to produce a magnetic flux tube that channels more than a million-ampere current between them. At certain times, we are in orbital alignment with that tube and as Io sweeps past our line of sight the flux tube channels radio energy our way and we get what are called Io radio storms. They can be quite dramatic.