'70s signal - what was it?

I have listened to SW radio for years (though not so much these days).
There was a radio signal years ago (1960s and 70s I think) that was a pattern of ticks.
I have always wondered what it was.
It is not the "Woodpecker".
This was (if you can follow this) two regular tic patterns with period very slightly different.
Something like 25 Hz and 25.01 Hz for example.
So you would hear this repeating pattern of "beat frequencies", repeating about every minute or maybe twice a minute.
I have not heard it for decades now.
I was hoping someone would recognize my description and tell me its popular name, or what it was.
Thank you,
Harvey

NOT the Russian Woodpecker?

Are you thinking of time-signals like these:
Time signals: JJY, BPM, BPC, WWV, WWVH, WWVB, RWM, DCF77, HBG, MSF, DX LF MF

Wirelessly posted (Moto Droid Bionic: Mozilla/5.0 (Linux; U; Android 4.0.4; en-us; DROID BIONIC Build/6.7.2-223_DBN_M4-23) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30)

Could it have been one the tropical band Cubans that had a clock running in the background of its programming? (I can't think of the network right now...)

harveyab said:

I have listened to SW radio for years (though not so much these days).
There was a radio signal years ago (1960s and 70s I think) that was a pattern of ticks.
I have always wondered what it was.
It is not the "Woodpecker".
This was (if you can follow this) two regular tic patterns with period very slightly different.
Something like 25 Hz and 25.01 Hz for example.
So you would hear this repeating pattern of "beat frequencies", repeating about every minute or maybe twice a minute.
I have not heard it for decades now.
I was hoping someone would recognize my description and tell me its popular name, or what it was.
Thank you,
Harvey

Click to expand...

Some other parameters might help a bit, such as frequency and how wide the signal was.

On the surface of it I would say you are describing an OTHR. Not Woodpecker, but maybe one of the US OTHRs, possibly MADRE, WARF, FPS-95, FPS-112, or FPS-118. A 25 Hz rate was common to all of those at one time or another, although MADRE and FPS-112 were pulse radars while the others were FMCW radars. This means that although they may have had the same rep rates they would have sounded different, but without more detail either type is possible. FPS-118 was in the late 70’s though, so if you are describing something heard through the 60’s and 70’s it is probably not a possibility.

T!

Cuban news station Radio Reloj has a tic-toc background with a morse code "R R" at the top of each minute.

Russian time station RWM 4996khz, 9996khz (and the now silent RID 5004khz, 10004khz) have a 'chucka-chucka-chucka' sound on certain parts of the hour.

That was way before digital comms, so there wasn't much beyond CW and RTTY.

Maybe it was WEFAX!

http://www.youtube.com/watch?v=StawpBfc2c4

k9rzz said:

NOT the Russian Woodpecker?

Click to expand...

Right. I have listened to the YouTube audio of the Woodpecker and that is definitely not the sound I am talking about. My original post description is the best I can do for now, I am thinking about trying to create a simulation of the sound, but that's a project that may take some time.
Thanks,
Harvey

Here is a YouTube video that I created as a simulation of the signal as I remember it. Does anyone remember hearing this? What was it?
https://www.youtube.com/watch?v=LucMRstsfBY

Thanks,
Harvey

Do you live near a hospital? Shortwave diathermy? Never head it myself but I guess that was a big noise generator back in the day.

harveyab said:

Here is a YouTube video that I created as a simulation of the signal as I remember it. Does anyone remember hearing this? What was it?
https://www.youtube.com/watch?v=LucMRstsfBY

Click to expand...

OK, your example has 2 slightly out of sync pulse rates, one is about 28.7 Hz and the other is about 28.8 Hz (eyeball measurements). However, getting that “walking” affect does not take 2 signals out of sync. It can also be produced by multipath and fading on a single frequency source.

The two frequency source does it by the affect you have shown, and is great with a sterile and constant level signal, the single freq source does it via variations in sound amplitude that tells the ear there is more than one thing present. So the question is, did you measure two rates present in the 60’s and 70’s? Or did your ear tell you there were two there?

What you have simulated really does sound like a radar to me. Possibly 2 radars (or two beams from one radar source) on one freq or overlapping freqs, with interleaved sweeps, either at different sweep rates or appearing to have different sweep rates because of delays.

The video below is a recording of the PLUTO radar. I am not saying this sounds like what you have simulated (and it would not have been on the air at that time) I am only saying this is similar to what you have there, without the walking. A couple of notes on the video, for the first 30 seconds I am in USB, for the next 30 seconds in LSB, and the final 30 seconds in AM. The purpose of hitting those modes was to show viewers what the sound might be like in the modes they are using. I did not make that video just to compare to your sound, but rather as part of the example signals I have on my YouTube channel.

Radar, PLUTO, 25 Hz mode, 12300 kHz, November 17, 2012, 1520 UTC - YouTube

T!

Thanks all for your thoughts.

My reproduction simulation is really how it sounded. It was VERY much the same all the time. Definitely two pulse trains, slightly different frequencies. Definitely not drifting or multipath stuff. The time for each "walking" cycle was always just the same. I listened to it many times over several years. It was somewhat broadband, and quite strong - easy to find, hard to miss. Don't remember what frequency area it was in, but at the time the radio I used had a top end of 30MHz.

No I did not live near a hospital. I live in western Washington state, about 4 miles from the nearest town.

If you ever heard the signal and remember it, you would definitely recognize my simulation of it.

The frequency of each pulse train may have been a little different, somewhere between 20 and 30Hz.

Harvey

Delete.

Sounds a lot like LORAN A

The Australians had "Jindalee" too, another OTHR - but it didn't last long (or did it..... :roll

majoco said:

The Australians had "Jindalee" too, another OTHR - but it didn't last long (or did it..... :roll

Click to expand...

Yes, Jindalee (JORN) is active every day Martin, from multiple sites.

T!

70's signal

That signal is LORAN A. I used to hear it on my old Hallicrafters S41G receiver on 160 meters back in the 60's.

LORAN A is an excellent possibility for what the OP is talking about. The timing would be about right also, the last station left the air in the 90’s, with many stations being turned off in the 80’s.

If the OP is describing LORAN A that should be pretty easy to narrow down to, it would have been below 2 MHz. He did not say the frequency range he heard the signal in, but when he said SW I assumed it was short wave and not medium wave and I scratched LORAN off the list based on that.

So I guess we need to hear from the OP, was the freq you heard this signal on below 2 MHz but above the top end of the MW broadcast band?

T!

I used to hear this stuff all the time on my dad's KWM1 and other receivers, so time frame would be late 1950s to around mid-60s.

I don't know what this one is, but one signal that he ID'd for me way back when which might be this one was CONSOLAN.

-dan

Thanks for identifying it.
When I read LORAN, it seemed to ring a bell.
Back then it would have been called just "LORAN" (the A was added later when there was a LORAN-B).
Yes it was above the US Broadcast band. I don't remember the frequency range any more.
So... Why, or how did LORAN-A use such a signal like this with the two slightly different pulse rates?
The sound always intrigued me when I was young. I guess it still does
I looked for a sample recording of LORAN-A on the net but didn't find any.
Anybody know of one?
Thanks again.
Harvey

harveyab said:

Thanks for identifying it.
When I read LORAN, it seemed to ring a bell.
Back then it would have been called just "LORAN" (the A was added later when there was a LORAN-B).
Yes it was above the US Broadcast band. I don't remember the frequency range any more.
So... Why, or how did LORAN-A use such a signal like this with the two slightly different pulse rates?
The sound always intrigued me when I was young. I guess it still does
I looked for a sample recording of LORAN-A on the net but didn't find any.
Anybody know of one?

Click to expand...

In the time period you are talking about, the 60's and 70's, it would have been called LORAN A, as LORAN B, C, D, and F had already been around or were in work. However, looking at my old log books I have just "LORAN" written down for LORAN A frequencies in the late 60's, I assume I did not care to add the A or C, or I did not know there was a difference at that time. I cannot say for sure, naturally, but this may have been common, I seem to remember most of the people I talked to just calling it LORAN.

Indeed, until researching this signal after you started this thread I did not know there was a LORAN B, D, or F, I only knew of LORAN A on medium wave frequencies and LORAN C on long wave frequencies. Since LORAN B used the same freqs as LORAN A and had a similar sounding signal even if I had been recording as LORAN “A” I likely would have called a B signal an A in my logs.

The reason for this signal, the nature of the clicks, is explained on the Wikipedia page for LORAN, and also on these pages:
Hyperbolic Radionavigation Systems
Loran History Home - loran-history.info

But basically the stations of the LORAN network send (or maybe “sent” is better) out pulses, the time relationship of each pulse from a given station (a station is 2 or more transmitters, each transmitter sending pulses in sync but out of time with each other) is known, and by measuring time of arrival for each pulse at your location you can determine 2 possible hyperbolic lines you are on from the transmitting station. Get a second set from another station and you now have 4 possible lines, but only 2 of these will intersect, one line from each station, and that intersection is your location.

I did hear a couple of recordings on YouTube of LORAN C, but none of LORAN A. There are some pulse and PRI differences between the two (as well as frequency) but the basic concept is the same. You might note on LORAN C recordings that you might not hear the walking nature of the signal you remember.

Keep in mind what I write below is how I understand it is supposed to work, based on what I have read in the last week or so. At the time LORAN A was active I never had a need to research it and understand the exact functions of the system. I heard it on the radio, logged it, and moved on. I sometimes did hear the walking sound you describe, but sometimes did not.

LORAN A (and C) worked as “sets” of master and slave transmitters on the same frequency. There can be multiple slaves to a given master. There was no walking sound to a given set, the pulses from the second (or third, fourth, nth) transmitter were at a constant delay from the pulses of the first (master) transmitter. Listening to one set you will not hear that walking sound you describe of two, or more, out of sync pulses.

Each set of transmitters worked at a pulse rate that was known and published from a list of about 2 dozen possible PRIs

It is only when you are in a location or under propagation conditions that allows you to hear 2, or more, sets on the same frequency that they will interact and you will hear the cyclic sound. The specific interaction can be extreme or very slight, depending on the location and set heard. The pulse rates could be very close in frequency, as in the example the OP made, or they could be very far apart, rates ranged from about 20 Hz to about 39 Hz in three ranges.

To the OP, thanks for asking the question, it made me read up on and better understand something that was just a memory from the past. If anyone in the forums here has any first hand knowledge of these systems, maybe worked in technical support, it would be interesting to hear that view.

T!