Missing 777

[madmax12]

Maybe a whale ate the pinger and that's why its moving.

Don't whales ping on the same frequency? On their own?

 

[Pixguy]

Don't whales ping on the same frequency? On their own?

Only when they eat cabbage.

I honestly thought this was a joke. Sorry.

 

[MossRoad]

Don't whales ping on the same frequency? On their own?

No. From what I read the manufacturers of the black box pingers specifically chose the frequencies they ping on because no other thing in nature makes sounds on those frequencies (cabbage eating whales may be the exception).

 

[madmax12]

No. From what I read the manufacturers of the black box pingers specifically chose the frequencies they ping on because no other thing in nature makes sounds on those frequencies (cabbage eating whales may be the exception).

Some scientist on npr was just explaining how the whales were having to modify their pings to be able to communicate "over" our pings.

Maybe I have misunderstood.

 

[dmccarty]

Great Britain, China, Russia and USA iirc are the four nations officially operating nuclear under water boats.

Lots of opportunity for games with those four players. The Aussies may try to slip a Collins class or two sub into the mix however. They are diesel electric and suffer short under water range. Rather quiet however at slow speeds or when stationary.

But only the US and the UK regularly send subs on missions. The Russians used too but now it is a big deal when the send a sub to sea and they are lucky the sub does not sink. The Chinese subs are worse than the Russian subs and some do not leave the dock at all though the Chinese are rabidly gaining skills in operations and building. They play for the long game. I doubt any sub leaving Russia or China is not followed by a US sub. That used to be true in the Cold War at least and I would really be surprised if a Chinese sub can leave the First Island Chain with out having a US sub following.

Later,
Dan

 

[madmax12]

http://article.wn.com/view/2014/04/07/Scientists_Search_Crews_Unlikely_to_Confuse_Black_Box_Pings_/

I don't know how accurate this is, but it is being discussed.

 

[Soundguy]

Don't whales ping on the same frequency? On their own?

suposedly the 35khz pinger was chosen because nothing in nature uses it. or at least that's what they say..

 

[k0ua]

I don't think any decent sonar operator would have any trouble distinguishing the pings from a biologic. Fox news showed an actual live screen shot of the waterfall display and it was easy to see the 37.5khz repetitive pattern of 1 second duration pings on 37.5khz. No biologic emits echolocation pings that would be so repetitive. Dolphins may occasionally use this frequency for echolocation but his pings are not going to look like the black box pings on the waterfall. Dolphins can emit pings up to 160 khz. Whales typically use much lower frequency's. For those of you not familiar with looking at a waterfall display, it is an x y display with frequency in the x domain and time in the y domain. I have been looking at PSK31 waterfalls for many years.

 

[k0ua]

For those of you that want to see what a waterfall display looks like here are some photos. Please excuse the Moire(interference) pattern to the screen, as apparently the scan rate of the monitor and the scan rate of the camera seem to set up an interference pattern on the photo. I will assure it does not look that way in real life. I suppose I should have taken a screen snap and saved it as a .jpg file.. oh well you get the idea.

This is the actual radio on 14.070Mhz. its display is showing the amplitude of the signals in its RF passband . in this case plus and minus 50 khz from the center frequency of 14.070 but the IF passband is set to 3.0 khz. So the audio sent to the computer will be restricted from about 100hz to 3.0 Khz. making the center frequency about 1500 hz. In the sonar rig, their center frequency is likely to be set to the 37.5khz and they will look for a small frequency band either side of that.

here you can see signals (PSK31 signals mostly and noise) through out the passband up to about 3.0khz. The cursor is set to about 2.260khz and is not currently decoding any signal at that location. The text in the receive window box is from previous decodes.

Here the cursor is set for about 1.675khz and is currently decoding the text you see in the window of a station in Germany calling CQ, and wishing to make contact. Notice that his signal is fairly weak, and notice the extremely strong signal on about 875hz.


Now you know more than you ever wanted to know about waterfall displays, And while these pix of radio signals and their recovered audio are different than sonar displays the concepts are the same. And the goal was to show you what signals look like on a water fall, and to help explain why I think no sonar operator would ever have any difficulty distinguishing the difference between a biologic (animal) and a man made pinger with a precise frequency and time domain signal.

And for those of you who know me well, yes I am a gun toting right wing redneck of the first order, but there is a technical side to me as well.

 

[madmax12]

That's cool James. Thanks :thumbsup: