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Search: Posts Made By: Mesoman
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Forum: Rumours & News
20th Jun 2014, 03:01
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Virtual terminal location?

First, kudos to RichardC10 for an impressive job and no doubt a lot of hard work.

One item that I find odd is the 718 km altitude of the virtual terminal (VT). This seems a very unlikely choice...
Forum: Rumours & News
9th May 2014, 04:18
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Woods Hole Expert

If the article is correct, this would be a bombshell.

But... I'd like to see someone else, or Woods Hole itself, corroborate this. After all, the pings were picked up by the experts using the TPL,...
Forum: Rumours & News
5th May 2014, 18:14
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

ULB propagation different from submarine

An important factor differentiating submarine sound propagation from ULB ping propagation is attenuation of the signal. At low frequencies used for submarine detection, there is virtually no...
Forum: Rumours & News
29th Apr 2014, 03:12
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Anyone know about this?

A CNN 'expert' said that they had not searched the bottom near the area of the first and longest ping detect, because it was too deep for the Bluefin.

This certainly contradicts the impression I...
Forum: Rumours & News
24th Apr 2014, 23:32
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

The techies are probably right

As a techie who also has SAR experience, I think there is very strong evidence that the techies are right.

The INMARSAT ping data is pretty good - I doubt anyone just made it up for fun. Even...
Forum: Rumours & News
22nd Apr 2014, 02:03
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Wreckage moving?

.


I really doubt this, but I'd love to hear from a maritime expert.

After a month on the bottom, it's unlikely it would still be tumbling. One would expect it to have reached a resting...
Forum: Rumours & News
17th Apr 2014, 02:09
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Density, pressure

For the purposes of estimating safe pressures, the density of sea water is virtually constant (variation ~1%), and thus the pressure is mostly linear with depth.

The small variations in density in...
Forum: Rumours & News
13th Apr 2014, 22:41
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

AIS Report source

I have noticed that Echo and Ocean Shield report at the same time. This suggests that a proxy is providing the reports - perhaps AMSA.
Forum: Rumours & News
11th Apr 2014, 04:22
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Echo now in the box

Earlier someone noted that Ocean Shield was departing the acoustic search box at faster than detection speed.

Now, Echo is in the box and almost stationary (.5 kts) - suggesting that they may be...
Forum: Rumours & News
8th Apr 2014, 19:25
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Questions on CNN recording

CNN just ran a video with the ULB pings in audio coinciding with a waterfall display. I have been unable to find this on the net - I would have expected it to be at JACC's media documents. Does...
Forum: Rumours & News
8th Apr 2014, 00:07
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Modern Signal Processing is not magic

This is true, and quite amazing results have been produced. But... you cannot repeal the laws of physics.

DSP can improve the effective signal-to-noise ratio. For some kinds of signals (coherent...
Forum: Rumours & News
7th Apr 2014, 21:26
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Why to doubt the Chinese

The Chinese did not record the signal, they just listened to it. This reduces the credibility a lot. It's very easy to hear what you want to hear - to imagine you hear a weak signal that is not...
Forum: Rumours & News
6th Apr 2014, 19:50
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Folks keep confusing RF and Audio - both have frequency

Quite right. A bit more explanation:

Audio signals, like those from the pinger, are *sound* - they are carried by pressure waves in a fluid.

RF (radio frequency) signals are radio - they are...
Forum: Rumours & News
6th Apr 2014, 05:09
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Not just semantics

This isn't just semantics.

When talking about signals, "continuous" has a specific meaning.

This signal is off over 99% of the time. That means the battery can last almost 100 times as long,...
Forum: Rumours & News
6th Apr 2014, 04:29
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Not a continuous tone

No, it's not a continuous tone. My only question is whether it has modulation. I have not read about that, so my bet is that it is not modulated.

You may be thinking of 121.5/243 MHz RF ELT's - a...
Forum: Rumours & News
6th Apr 2014, 04:17
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Widely separated ping detects, and probabilities

It is pretty hard to come up with a likely scenario that separates the boxes by 300mi. Possible, but pretty unlikely.

Angus Houston is pretty clear that these detects are iffy. However, he also...
Forum: Rumours & News
6th Apr 2014, 04:00
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Western ship just picked up a ping

Per the press conference, a western ship (Ocean Shield) picked up an acoustic signal about 90 minutes ago and is slowly turning around (with 6km of cable trailing) to try to sort it out. No more...
Forum: Rumours & News
6th Apr 2014, 02:14
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

China detection is fishy, so to speak

Not only that, the odds of it stumbling upon the beacon are very low. With detection ranges of only a few kilometers, only from a deep towed listener, it takes a very long time to cover a wide area....
Forum: Rumours & News
5th Apr 2014, 21:41
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

No. At the high ultrasonic frequency used by the...

No. At the high ultrasonic frequency used by the pinger, attenuation with distance is very significant, so the signal at detectable levels just doesn't go very far.

At much lower frequencies,...
Forum: Rumours & News
30th Mar 2014, 23:15
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Too much faith...

You are putting too much faith in the capabilities and alertness of the relevant militaries.
Forum: Rumours & News
29th Mar 2014, 07:11
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Probabilities

It's important not to look at unconditional probabilities.

For example, it is highly unlikely that a specific flight will end up the way MH370 did. And yet, MH370 had the extremely unlikely...
Forum: Rumours & News
29th Mar 2014, 00:24
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Pinger detection

Submarines listen to low audio frequencies, which can travel very long distances underwater.

The pinger is at a much higher audio frequency (37Khz) which is attenuated (reduced in strength as it...
Forum: Rumours & News
25th Mar 2014, 00:43
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

ELT's - more info

Too add to the ELT info. I don't know the specifics of the 777 ELT's (some others on here have more info on this). However, the following is general information that will apply to detection and...
Forum: Rumours & News
24th Mar 2014, 08:32
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

EMP, EM - Not in this case.

EMP or EM has been mooted a couple of times as a possible cause of electronics failure in this incident.

That didn't happen. Aircraft operate in nasty EM environments as a matter of course. On the...
Forum: Rumours & News
23rd Mar 2014, 00:30
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

GPS through INMARSAT - still no tracking ability

I can understand the concern, but INMARSAT still uses normal SBAS transponders, like on other satellites. They transmit a pseudo-GPS signal on 1575.42Mhz via a "bent-pipe" transponder. The only...
Forum: Rumours & News
22nd Mar 2014, 20:34
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

GNSS receiver - no, you rally can't track it

Yes, which has nothing to do with tracking a receiver.

:ugh::ugh:
Forum: Rumours & News
22nd Mar 2014, 20:23
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

GPS receivers don't transmit!

Sadly, popular media showing people being tracked by the GPS receivers has confused too many people. GNSS (GPS/GLONASS/...) receivers do not transmit anything. They only receive. They receive signals...
Forum: Rumours & News
21st Mar 2014, 05:04
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

P-3 Crews, and air sickness...

Yep. I've been on lots of P-3B flights with (side facing) nugget sensor operators. Sub hunting involved flying lots of low level patterns. We always made them clean their own barf off their consoles....
Forum: Rumours & News
20th Mar 2014, 07:54
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Not stereo Pair

No, the photos represent different ways of looking at spectral information. The one on the left is brightness from all wavelengths together (monochrome). The one on the right is false color, showing...
Forum: Rumours & News
20th Mar 2014, 05:41
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Sonar

I wouldn't know about the subs, personally. I did help train Aussies and Kiwis in P-3's. I notice that the P-3C endurance (10 hours) is quite a bit less than in the old days - perhaps all the fancy...
Forum: Rumours & News
20th Mar 2014, 05:31
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Coordination likely not a problem

I doubt it. Both aircraft types are US Navy types and the OZ and NZ crew probably trained at US Navy facilities (we trained them decades ago on older P-3's).

They are also all operating from the...
Forum: Rumours & News
18th Mar 2014, 19:33
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Pings, SAR and probability

Per the recent discussion on what additional satellite ping data (about which we have not been given info) could provide...

It is unlikely that the additional pings would tell us exactly where the...
Forum: Rumours & News
18th Mar 2014, 08:21
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Odd shaped search pattern. Any ideas?

Today's search pattern is a funny shape. Anyone know why?

The press kit for the Aussie SAR operation for 18th is at:...
Forum: Rumours & News
16th Mar 2014, 19:58
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

Tracking an aircraft - doppler

This approach is not relevant to the current event.

Until a few years ago, 121.5/243.0 MHz ELT signals were located using doppler from the COSPAS/SARSAT satellites. On one pass, the doppler...
Forum: Rumours & News
15th Mar 2014, 19:47
Replies: 11,831
Views: 24,185,847
Posted By Mesoman

A few radio technical comments

I've been reading the thread, and have a few comments based on my radio/RF Engineering/software/comms background (my aviation is only P-3 aircrew, private pilot, and CAP SAR):

"Ping" - we don't...
Showing results 1 to 35 of 35


 
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