[teraflop]

> show a sinking titanic was heard both in london and new york, but a modern(...ish) MH-370 can just dissapear?

What do you mean by "heard both in London and New York"? The Titanic was actively sending out distress signals via telegraph as it sank, but those signals weren't strong enough to reach land. They were picked up by other nearby vessels and relayed.

[Gordonjcp]

It was night time. Titanic's radio transmitter could work on both 500kHz and 1MHz, pretty advanced stuff for the time, and the bands were far quieter.

It would have been hard *not* to hear it on both sides of the Atlantic, even with the primitive receivers of the day.

[kQq9oHeAz6wLLS]

Plus, lower frequencies generally have an easier time traveling long distances, especially over saltwater (and at night, hence the first part of your response).

And to answer the question about why we can't use lower frequencies on planes, part of the answer lies in antenna length, which is related to wavelength. Lower frequency = longer wavelength, which in turn means larger antenna (yes, I know this is a very broad generalization, and also not the complete/only reason). Look up the antenna required for 1Mhz.

[Gordonjcp]

The lowest band my amateur radio licence allows me to use is 136kHz, which would require a dipole about 1km long and at least 50m off the ground.

You wind a loading coil on a plastic dustbin.

[dylan604]

>via telegraph

?? Is there a different meaning of telegraph than I’m familiar that works without direct connected wires?

[detaro]

wireless telegraphy was/is a common name for sending text (especially as morse etc signals) over radio

[FreshStart]

So why can't we have aircraft screams some data in a last ditch effort?

[touisteur]

As long as you trust the pilot with absolute authority over which equipment is running, this isn't going to happen. If something can catch fire (as in, any electronics?), it needs to have some kind of local breaker that the flight crew can switch off. The only trusted equipment there is one doing passive recording of some elements (the flight recorder).

[bombcar]

The airframes do usually have various ELTs and beacons that can activate in a crash, but some (most?) can be disabled in some way (in case they’re accidentally on) - and others are only short range/directional.

[dghlsakjg]

We do. The radios they use can be heard for quite a distance at the altitudes they operate at