530 Kilohertz, Odd noise

Greetings, ATSers. I've got a question for you guys and gals. Every day and night for the past year or so now, I've driven past a small area where my radio will pick up the same noise over and over again. It's a very small area in the city of Sanford, Florida, lat: 28.81197 long: -81.33512. It's a stretch of road between the intersections of Rhinehart Road and SR 46, and right before the Interstate 4 overpass. So...Approximately a 550 meter stretch of area where this strange noise will be picked up. My question to you folks is...what could it be? I'm not quite sure how to upload a sample of the file, but I have about a minutes worth of it repeating. I used a phone as a recording device, so it doesn't pick up the bass tones very well, but when it reaches the end of the cycle, it is a particularly low rumbling tone. Can anyone explain to me how to upload this sound sample so we can figure out what the source of this emanation is?

I would guess it would be a traffic bulletin transmitter used for giving motorists a heads up in construction projects or severe weather conditions. You did not state that you heard any recording on the signal so I would imagine it could be broadcasting silence until a new recording has been loaded.

Could be many things. Right below the AM radio band many people setup hobby transmitters for medium and long wave experimental transmitting using methods as simple as morse code to more complex stuff such as data bursts.
As the person above me said it could be a TIS (Traffic information station) that just happens to have a cruddy transmitter causing a wobbling sound.

Also people are allowed to use Part 15 accepted power levels to broadcast whatever they want on the AM broadcast band in the 100 milliwatt range. Frequencies below the standard AM BCB are called Longwave frequencies and some of those frequencies people are allowed to use up to 1 watt of transmission power unlicensed for hobby stuff or experimenting.
Of course everything above the AM BCB up to 30MHz is called "Shortwave" just for reference

There are quite a lot of beacons and data stations right below 530Kc which would explain what you could be hearing. If a station on a frequency a few kilocycles below 530 was operating even with really low power it could heterodyne with the well known Spanish station on 530 causing you to hear the beat frequencies of the two mixing together. This would allow you to hear something that may sound bizarre.

It's probably just some kind of data transmission and you are just able to hear it because it's mixing with another station on that channel, or someone is messing with that frequency out of experimentation.


[edit on 11/22/2009 by darklife]

530Khz falls in the range of Non-directional beacons for aircraft navigation

Couldn't be a hobbier because you said you hear it for about half a mile. What were you listening to in that frequency anyways(how did u find out about the signal)?



[edit on 22-11-2009 by daniel_g]

reply to post by daniel_g

It MIGHT be an aircraft nav beacon because the location is near an airport, but it shouldn't fade in and out over such a small area. it dissapears when travelling closer to the airport as well.
I was listening to 540 WFLA, a central florida talk radio station and I heard the noise spilling over into that frequency, and I tuned into the bands higher and lower than 540. My car stereo only goes down to 530, and it was just static on 550. It almost perfectly tunes in on 530 however.

Originally posted by daniel_g
530Khz falls in the range of Non-directional beacons for aircraft navigation

It cetainly does sound like a non-directional beacon. Used as navigational aids for air and watercraft, these signals are akin to modern day lighthouses. While these signals don't transmit additional navigational data -- other than their actual signal -- their "known fixed position" is, essentially, the data being transmitted.

Non instrument rated pilots or fishing boats at sea or out in a gulf or lake can use these non-directional beacons to help guide their course by knowing the charted fixed positions of the signal. Furthermore, if two or more of these non-directional signals are located. It would be possible for a ship or plane to chart their own relative location using these signals.

Anyway, it certainly makes sense. The signal that you picked up was near an airport and this is one place that would definitely make use of this particular technology. Even though there are far more advanced technologies currently available (ie. GPS), non-directional beacons continue to be one of the most widely used navigational aids in the world today.

[edit on 11/24/2009 by benevolent tyrant]

What kind of antenna is used to pick up the 530kHz signal? Is it a coil on a ferrite core?

reply to post by buddhasystem


it's just your normal car stereo antenna. I believe it's a coil though, since I don't have an extendable antenna. Newer model cars like my monte carlo (2004) have the antenna wrapped around the windshield.