Signal Heard Jamming WWV on Both 5-10 MHz

[dark_overload]

Yesterday morning around 0900 EDT (1300 UTC) I stumbled across these strange transmissions that seemed to drown out WWV entirely. It started again this morning while I was writing this thread. I first noticed it this morning at 0915 EDT (1315 UTC).

It looks (on spectrogram) and sounds to me like some sort of MFSK. As you can see in the band-scope images, the signal is present at the same position relative to WWV on both 5 MHz and 10 MHz, and the bandwidth of both signals is the same. As you can also see in the spectrogram images, it appears to be the same exact signal as well. For the same signal to be present in the same relative position on two different bands, my theory is that it was deliberate.

Twenty minutes ago, I was able to hear WWV just fine on 5 MHz. Now all I hear is the same buzzing you will hear in the 5 MHz sound file below.

Here are the band-scope images, lower frequency first:

Here are the spectrogram images, lower frequency first:

Finally, here are the audio recordings, lower frequency first:
Freesound.org - "5mhz_jam.wav" by dark_overload
Freesound.org - "10mhz_jam.wav" by dark_overload

I have racked my brain trying to figure out what in the world this could be, and the best I can come up with is that it is some foreign military's attempt to jam our standard time signals. The fact that it sounds like innocuous noise to the untrained ear, and the fact that I cannot decode it no matter how hard I try, even in spite of the fact that it is clearly a digital transmission of some sort, is what lead me to this conclusion. I am open to other ideas so please, if you have anything to contribute, let me know what you think.

Also, as I am hearing this right now, completely drowning out WWV on 5 MHz, and overlapping WWV on 10 MHz, please let me know if you hear this signal as well, or have heard it in the past. I would like to try and find out if this is a local source of noise or what. I live in FL though, so for all I know it might be coming from Cuba.

 

[dark_overload]

Poof

Just like yesterday, the signal is now gone, just as quickly as it appeared.

 

[jim202]

Just like yesterday, the signal is now gone, just as quickly as it appeared.

You need to prove that it is not an image of another signal on another frequency or something locally causing what your describing. You could have leakage from cable TV, the local oscillator from another receiver or even a computer generating this signal.

With you not providing a hint of just where your located, it would be hard for others to verify what your telling us.

 

[dark_overload]

Location

Those audio recordings are geo-tagged, I live in Satellite Beach, FL. And I suppose that if you don't trust that I am being honest about my findings, then I really can't do much to change your mind about that. I've ruled out any equipment at this QTH by process of elimination. The dates on the spectrogram images are incorrect, because I rendered the images from recorded WAV files, and the date shown is the date of render, not the date of recording. They are rendered from the same WAV files that are posted and geo-tagged on freesound.org in fact.

It seems that if I was to listen to 5 MHz at around 9am local time, it starts to drown out WWV, and then within an hour, they are both gone and all I hear is the ether. My guess is that daytime conditions on those bands are responsible for both of their disappearance, but where this signal comes from, and why it is strong enough to wipe out an S5 signal from WWV is the real question.

 

[zz0468]

That just sounds like a local noise source.

From Florida, WWV at 5 MHz is going to be barely audible, if at all. As the ionosphere get's exposed to the sun, absorption on the lower frequency goes way up, to the point that some frequencies become useful for local ground wave communications only. 5 MHz is a night time band.

 

[dark_overload]

HF Concepts

I am familiar with the way the bands behave at certain times of the day, I've been a general class ham for two years or more. So you're saying that as the D layer starts to absorb WWV, my receiver is getting more sensitive to a local noise source? How come it disappears within an hour? If it was local, shouldn't it remain all day? I dunno, maybe there are more complex methods of propagation taking place along the greyline to bring in a distant signal for a short period of time. But then why would it happen two days in a row at similar times?

HF never ceases to amaze me...

 

[Token]

Those audio recordings are geo-tagged, I live in Satellite Beach, FL. And I suppose that if you don't trust that I am being honest about my findings, then I really can't do much to change your mind about that. I've ruled out any equipment at this QTH by process of elimination. The dates on the spectrogram images are incorrect, because I rendered the images from recorded WAV files, and the date shown is the date of render, not the date of recording. They are rendered from the same WAV files that are posted and geo-tagged on freesound.org in fact.

It seems that if I was to listen to 5 MHz at around 9am local time, it starts to drown out WWV, and then within an hour, they are both gone and all I hear is the ether. My guess is that daytime conditions on those bands are responsible for both of their disappearance, but where this signal comes from, and why it is strong enough to wipe out an S5 signal from WWV is the real question.

I know I did not bother to check the geo-tags on the audio, nor do I as a regular thing. So many people are using remote receivers these days that just because a signal was recorded in one location does not mean that is where the signal was received.

When a person posts to any radio related forum / group and starts talking about something they are hearing it is most common for them to include at least a general area of the receiver used in their post or maybe in their signature. Your original posting included nothing of the sort, and so jim202 had a perfectly valid comment.

So far no one has questioned the honesty of your "findings", so not sure why you made the comment of "And I suppose that if you don't trust that I am being honest about my findings, then I really can't do much to change your mind about that." Jim202 only said you need to confirm it is not local noise. Local noise can be outside of your QTH also, all the way to the local horizon can be "local" noise.

As an aside, I have recordings of WWV at the time of your report, and there is no sign of any similar noise on my recording. I was recording (and do frequently) around 1300 on both 5000 kHz and 10000 kHz looking for other time standards, at that time of the morning BPM out of China is normally in very strong here. Also at the time I had good propagation from several Cuban stations on near frequencies, so if the source of your noise were Cuba I would have likely caught some indication of it on my recordings.

You said in your first post "the fact it is clearly a digital transmission of some sort". I am not at all sure of that. In fact it sounds rather like a local noise source I have seen before. Why are you convinced it is an intentional digital transmission? The rest of that sentence is "The fact that it sounds like innocuous noise to the untrained ear, and the fact that I cannot decode it no matter how hard I try, even in spite of the fact that it is clearly a digital transmission of some sort, is what lead me to this conclusion." And leaves a lot of questions or room for comment. I assume your ear is trained? You cannot decode it, however, that is not unusual even if this is/was a digital signal, more digital signals are heard each day that cannot be decoded than can be decoded. But even the ones that cannot be decoded can generally be identified as to type of transmission.

Further, more details of how it was received might help quite a bit. What was the receive mode used for the recordings? What was the bandwidth of the receive filters? The audio bandwidth of the recording is 3 kHz, but was that the edges of the filter, or was that the edges of the signal? What was the receiver type used? What was the antenna? Do you live in an area where noise might be an issue?

Frankly, this sounds like some kind of local noise to me. With its base ~6 Hz cycle (run it into a scope and look for the repeating peaks) I would be at a loss to tie it to any digital format. Also, the pulse rate shifts slightly for the short duration of the audio recordings, and that means the ?data rate? is not stable, again supporting an unintentional source.

For a while I had a neighbor about 600 yards away with an automated outside light. Every morning about sun up and sun down a very similar noise (with regard to the spectrogram) to yours came on the air (but around 6600 kHz). It would trigger on and off several times in the + / - 45 minutes of dusk / dawn, each time being on for roughly 10 minutes per burst. So every day, 5 to 8 times a day, I would have this noise from his light controller. It took over a year to figure out what it was. Now, I am not saying this is the same source as your issue, what I am saying is that it might take a bit of searching to find it.

T!

 

[zz0468]

I am familiar with the way the bands behave at certain times of the day, I've been a general class ham for two years or more. So you're saying that as the D layer starts to absorb WWV, my receiver is getting more sensitive to a local noise source?

I don't think it's your receiver getting more sensitive so much as local noise sources increasing during the day.

How come it disappears within an hour? If it was local, shouldn't it remain all day?

Not necessarily. HF propagation can change minute to minute, and so can noise sources. Temperature and humidity, for example, can change the behavior of power line noise, and since those conditions can be linked to daylight or night time, noise levels can change depending on time of day. That's just one of many, many possible explanations.

I dunno, maybe there are more complex methods of propagation taking place along the greyline to bring in a distant signal for a short period of time. But then why would it happen two days in a row at similar times?

Because D-layer abortion is going to occur at about the same time every, depending on the season.

HF never ceases to amaze me...

Yep, same here. And I've been playing with it for over 45 years. It never gets old.

 

[dark_overload]

Thanks

Both of you guys have given me a lot to think about. Those "jumps" that Token speaks of is what made me think it had something to do with composite video, scene changes sound the same, maybe a leaky cable amp somewhere. But it didn't sound like an analog video signal. I am still confused as to exactly what it is. It may or may not be deliberate, but it definitely sounds man-made.

Yes the AF bandwidth is 3 kHz, because the maximum SSB filter width on my radio is 3 kHz. Those are both recordings of the upper sideband portion of the time signal. That recording is only a portion of the noise though, because it is approx. 10 kHz wide (as you can see in the band sweeps at the top of the initial post) and I could not widen the filters enough to get it all.

Thank you both for your intelligent feedback.

I am new to this board, by the way, so I haven't set a location or radio info yet. Sorry.

I use an IC-7000 with an LDG AT-100ProII in the shack, and for antennas I use a custom built 20/40-meter perpendicular leg inverted vee di-pole on a 1:1 balun and a Tram 5/8 wave dual-band ground plane vertical, both atop a 30 ft. push-up mast.

I will edit my profile later today so that next time there will be less to wonder about.

P.S. When someone tells a person to prove something, it implies that they do not believe what that person is saying. That's where that came from.

 

[majoco]

Aren't WWV experimenting with a different data transmission mode?

 

[nd5y]

No. That was WWVB on 60 kHz that did that a while back

 

[Confuzzled]

the best I can come up with is that it is some foreign military's attempt to jam our standard time signals.

:lol:

I needed a good laugh today.

Maybe it's a homing signal for 'them'.

 

[NK7Z]

WWV Jammer...

Hello,

There is an interesting discussion regarding this signal on the Yahoo group Dopplergrams. Peter M, (developer of SBSpectrum) has done some fingerprinting of the signal. You may be interested in reading this information.

Dave
NK7Z

 

[Token]

Hello,

There is an interesting discussion regarding this signal on the Yahoo group Dopplergrams. Peter M, (developer of SBSpectrum) has done some fingerprinting of the signal. You may be interested in reading this information.

Dave
NK7Z

Do you have a link to the specific post in that Yahoo group concerning this signal? I have gone through all of them and while I see a lot of signals being discussed around time standard frequencies and stations I do not find this particular signal.

T!

 

[dark_overload]

Link

Yes, please share the link if you have it. I'd love to know what the heck this signal is, and I'm glad I'm not the only one who heard it.

 

[NK7Z]

Location within Dopplergrams...

Start with post number 320, and work up in number...

Thanks,
NK7Z Amateur Radio reviews and software setups

 

[Token]

Start with post number 320, and work up in number...

Thanks,
NK7Z Amateur Radio reviews and software setups

I see nothing describing a signal similar to what the OP linked. I do see them discussing "other" transmissions on 10 MHz, but not any like what the OP reported. Specifically in the 4 or 5 posts before #320 they appear to be discussing a USB+carrier signal with time pips and voice announcements and how the carrier changes frequency, possibly as heating / cooling occurs.

T!

 

[dark_overload]

Dopplergrams

I'm afraid to get on Yahoo! anymore after that whole hacking incident... I mean, really? Why were none of those passwords hashed before storing to the database? In my network security class we talked about "due diligence." They are going to get sued, and not only do I not want to accidentally agree not to sue them in some TOS update they spring on me upon my next login, but I cannot trust them with my new password sets.

Yahoo! sucks, I'm ranting I know. I'm sorry if I offended anyone who happens to like them. Long story short, I wish there was something in that group worth making a disposable account for, but I'm not bothered that there isn't. This is because (as I do sometimes when I hear of a new method of analysis) I studied what a dopplergram is, and what it's used for. I find it fascinating. It's an excellent way to study the behavior of the ionosphere over time, as well as many other aspects of HF propagation.

You learn something new every day, and now I have another tool in the box so to speak.

Thank's Dave.

 

[dark_overload]

Update

Not to beat the horse even further, but I've uploaded (and they've finally approved) a 30 minute recording of the digital/noise/interference signal just in case anyone wants to make closer examinations. Here is the link.

Freesound.org - "5mhz_jam_long.wav" by dark_overload

 

[brandon]

The noise source is from a Plasma TV.
Here is a Plasma TV QRM heard from my location: http://solarix.org/audio/plasma_noise_cancel.mp3
You can cancel it out using something like the MFJ-1026 or Timewave ANC-4. (which I did in the clip above)