strange sounds above AM band in the 70's

[flytrap]

This has always puzzled me. When I was a kid growing up in the 70's you could hear some strange electronic sounds coming from the am band if you jammed the knob all the way past 1600Khz. I'm guessing around 1620 or 1630 since I didn't have digital read-out back in those days. The signal was pretty strong and didn't seem to be coming from my house. This was before most digital devices were around to create noise. The sounds were similar to the strange whoops, chirps and horn sounds that is common on shortwave, or the sounds that you might hear when you place a calculator or other electronic device near an AM radio. The sounds would often change pitch. Mostly it was just a "horn" noise. It could also be heard on the car radio. I know that there was a gas well and sulpher plant a few miles away, so I always thought it was maybe something that they were doing. I remember hearing it as far back as I can remember, but it seemed to disapear sometimes in the late 70's or early 80's. The signal was strong in my location (central Mississippi) Does anyone know what that might have been?

 

[Schroedingers Cat]

There were some kind of navigational beacons in this range. They had a carrier shift or varying amplitude component. You needed some kind of BFO or another radio with the oscillator tuned near the frequencies to hear different tones. There was one in the 1970s that operated near Harrisville, Michigan. I always thought they were marine type beacons. I could hear it at night over a hundred miles away and went right by the harbor with the transmitter with a receiver with an S meter. It changed amplitudes at one frequency, but that could also have been a carrier shift. By creating a local oscillator signal, I determined that it was a carrier frequency shift.

 

[Matt]

It could have been WEFAX or maritime navigational chart transmissions. Old-style slow-speed fax would have made that chirping sound. It was used to transmit facsimile copies of weather maps, charts and other communications useful for ships personnel on the oceans, Mississippi or Great Lakes.

Most of those transmissions were moved to satellite and later to internet so that the warbling and chirping disappeared by the end of the 70's.

Something I found interesting about the uses they put the 1610 - 1700 band of frequencies to...some stations were licensed in this band for remote pick-up transmitters for broadcast stations in the 30's and '40's, but generally the band fell into disuse for much other than navigation and weather aids from the early 50's until international treaty opened it up for AM broadcast in the early 80's.

Later.....

 

[kilokat7]

The radio bug hit me while growing up in the 80s. As such, I remember picking up cordless telephone calls just above the AM dial. The modulation always sounded funny. It wasn't later until I discovered they used FM. Anyone else remember hearing these in the 1700 kHz range? These were before the 46 mhz cordless phones.

 

[boiseengineer]

Beacons for keeping track of fishing nets were up there.
For a while cordless phones used above 1700 for the base unit & 49 MHz for the handheld.
Since they were so far away from eachother frequency wise there was no need to filter the reciever from the tranmitter part.
I'm so old I remember listening to Southern California PD.

 

[flytrap]

Speaking of the cordless phones on AM, a quick reference to wikipedia says they operated from 1640Khz-1780Khz. Even though AM radio only extended to 1600Khz, most radios would tune a little past 1600 if you turned the knob as far as it would go. I remember hearing a cordless phone on my college roomates stereo back in the early 80's. My roomate came in and wondered what I was listening to. Before I knew it the dorm room was full of people listening to this guy talking to his girlfriend. As word spread, half the building had it blasting out of their stereos. It turns out it was a guy on an upstairs floor. Even people in different buildings were trying to listen. It only lasted a few days before someone tipped him off. One day I heard his girlfriend say "You're not using that cordless phone are you? He said yes, and she abruptly hung up, anyway, it was a naughty thing to do, but it was entertaining while it lasted.
I once picked up a cordless phone while trying to fix an old antique radio. Since there are no houses within a 1/4 mile radius, those phones must have gotten out quite good. Much better than the 49MHz and 900Mhz phones do today. I would be nervous about using one today since the AM radios will now tune those frequencies by default.

 

[Cincinnati Kid]

On some of the older (1950's or so) electric radios, it was possible to tune the AM dial up into what must have been the 1700's. I'm not sure what the exact frequency would have been, but in 1962-63-64, I was able to receive base-to-car dispatches of the Cincinnati Police Department. While reception was usually better the closer you were to the downtown area, there were several times when I picked up these on a radio while in south-central Kentucky.

 

[mimo]

There was once a time when the police band was 1700 khz. Some very old radios I've seen from the late 20's early 30's would tune up that high, and right above 1700 it said "police" in small letters. Then FM technology came about and I guess the police adopted the current band as it was less susceptible to interference.

 

[Schroedingers Cat]

My Uncle, the one who lived in Park Ridge near the WJJD array until late in life, spent the early part of his life in Michigan and was with the Michigan State Police for a number of years, when they still used the 1600-1720 kHz Police Band. There was a State Police handbook that my grandmother had kept when he moved out of state that talked about the skip "problem" they were having, and about contacting out of state police departments that heard the calls and relaying information. At that time, cooperation with other states was the way they dealt with the skip "problem".

The portable phones in the 1600-1800 kHz range used narrow band FM, and it was necessary to use slope detection to hear the calls on an AM radio. If you unplugged the base unit, you could hear nearby calls on the portable phone, in crystal clear narrow band FM. Luckily, I immediately knew how to use slope detection with the AM radios, or I would have missed the interesting calls. Interestingly, it was never illegal to listen to portable phone calls. When powerful people began using the first cell phones, laws were passed to make it illegal to listen to cell phone calls. Strange, because without being tipped, there was no way to know who you were listening to without them revealing their identity during the call, which is rare in the short snippets you were likely to be able to hear a call from a portable or cell.

 

[flytrap]

Speaking of cell phones. If you had a television set made before the 80's you could pick up cellphones by tuning to the upper end of the uhf band around channel 83 and adjusting the fine tuning knob. Newer sets only tune up to channel 69, but a few b/w sets were still being made that tuned all the way to channel 83 up until digital tuning replaced knob- type tuners. The last time I heard a cell phone on TV set would have been in the 90's. I doubt you would hear much on upper UHF tv with today's newer digital phones.

 

[Schroedingers Cat]

They scrambled the audio before they went digital. Notice that they stopped selling the UHF model at Radio Shack, along with blocking the cell phone frequencies on scanners. I wonder if the government would have been as concerned if the cell phones had started out in all hands and not just the powerful. You had to have a local oscillator to detect and hear stand alone FM signals on TVs.

 

[pqgeorge]

There were a multitude of unusual signals above 1600 kHz, back in the day (in the early 70's). I recall hearing a dual tone transmission around 1620 or 1630 kHz in the Boston area. The funny thing was if you used an AM radio with a ferrite bar antenna, if you turned the radio one direction.... one tone would be favored. Turn it the other way the other tone be favored. It must have been some form of radio-navigation system. I believe there was a transmitter in the Boston area. It did sound like a horn of sorts but kept sounding continuously. It was using a considerable amount of power as it sound pretty strong about 30 miles inland. It also had some skywave propagation characteristics at night as well.

 

[flytrap]

I was a little kid when I remember hearing them on my little portable radio. I'm glad someone finally cleared that up and I'm not crazy. Years later when I got a shortwave radio and heard similar sounds, I figured that it must have been some sort of beacon or electronic device. Haven't listened to shortwave in a while, but back in the day you could hear some mighty weird stuff. Foghorns, woodpeckers, strange audio phasing signals (what was that?) and numbers stations, which made absolutly no sense to a 14yo kid. Had a friend who had a portable radio that picked up shortwave. I showed him some of these strange stations and he would trip out on weed while listening to the beeping time signals on WWV. Being a good boy myself I never indulged in that activity. I just set the clock on the VCR with it.

 

[Cincinnati Kid]

There was one "sound" on shortwave that I remember that sounded like a propeller-driven airliner in flight. When you tuned onto it, the signal would drift just slightly so you had to continually adjust your dial to hear it to its full effect. I'm still not sure what that was.

Seeing the mention about WWV makes me recall another another shortwave station that gave the time. It identified itself as "Dominion Observatory Canada" and it would give the Eastern Standard Time. I've always wondered where that was coming from.

 

[radioman148]

There was one "sound" on shortwave that I remember that sounded like a propeller-driven airliner in flight. When you tuned onto it, the signal would drift just slightly so you had to continually adjust your dial to hear it to its full effect. I'm still not sure what that was.

Seeing the mention about WWV makes me recall another another shortwave station that gave the time. It identified itself as "Dominion Observatory Canada" and it would give the Eastern Standard Time. I've always wondered where that was coming from.

The "Dominion Observatory" station was CHU out of Canada. Ottawa--I think. I remember that airplane propeller engine sound on short wave. I always wondered what it was when I first heard it back in the 60s. I read an article once that mentioned it was jamming, but I was never sure.

 

[Darth_vader]

The F¢¢ ruled in 2008 that the ¢ellular systems were no longer required to carry AMPS service, so most (if not all) of the major ones dropped it rather hurriedly. It may be possible to bring your 70-83 receiver or your PRO-2004 to some far-flung "remote" area somewhere (read: out in the sticks) and hear some occasional AMPS traffic, but these days it's a GSM/?DMA world where the major populated areas are concerned.

Gone are the days when I could turn on my VCR and monitor the gossip of the local social set, drug deals in progress and questionable business being conducted between high-profile persons in the community; not so much "legality" (not that it was ever enforceable to begin with) but due to changing technology. Oh, those were fun times.

"Most of those transmissions were moved to satellite and later to the Internet, so that warbling and chirping disappeared by the end of the 70's."

Nope--weatherfax is still very much in use (especially by NOAA and "Environment Canada" or whatever it's called) so it's still possible to encounter such signals on shortwave today, in 2013. NMC and NOJ are received quite regularly here, and KVM70 when I'm at the coast.

http://dxinfocentre.com/rafax.htm
http://dxinfocentre.com/hepburn/fax_dx_sw.html

"There was one 'sound' on shortwave that I remember that sounded like a propeller-driven airliner in flight. When you tuned onto it, the signal would drift just slightly so you had to continually adjust your dial to hear it to its full effect. I'm still not sure what that was."

Probably a jammer. Some of them got/get their "audio feed" by putting a microphone near the diesel generators powering the things, which is why they sound/ed like a semi truck. I recall hearing one (probably Cuba) jamming the Armed Forces Radio Service SSB channels in Key West, FL about 3-4 years ago.

 

[BDM123]

The radio bug hit me while growing up in the 80s. As such, I remember picking up cordless telephone calls just above the AM dial. The modulation always sounded funny. It wasn't later until I discovered they used FM. Anyone else remember hearing these in the 1700 kHz range? These were before the 46 mhz cordless phones.

Yes I remember those short lived cordless phones in that band.

 

[Darth_vader]

I do remember the 46 (and 49) MHz cordless fones; the mediumwave ones were probably before my time. Mum used to have an old late 1980s AT&T cordless/speakerphone unit (actually she still does have it, now that I think of it) and I used to perform "service monitoring" on her quite a bit as a kid armed with a simple 20-channel police scanner.

In fact, I happen to know of one such 46 MHz cordless that's still curiously in use at a neighbour's place to this day, not more than 100 feet or so away from the machine I'm writing this post on. They're going through a really nasty divorce right now, so it does make for some rather, erm, "interesting" monitoring...

 

[boiseengineer]

The airplane noise is/was actually multi-channel RTTY transmissions. I forget how many channels stacked in a row but the carrier shift for each channel was really small. I used to decode them with an AEA decoder connected to a Commodore 64!
Mostly news feeds.

 

[radioman148]

The airplane noise is/was actually multi-channel RTTY transmissions. I forget how many channels stacked in a row but the carrier shift for each channel was really small. I used to decode them with an AEA decoder connected to a Commodore 64!
Mostly news feeds.

Thanks boiseengineer. I always wondered what that was.