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Mystery signal from a helicopter

windytan.com

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Re: Mystery signal from a helicopter

#52

Post by easy_rider »

jgrahamc wrote: post #13

I love Oona Räisänen's blog. She's my hero. She combines a love of figuring stuff out with lots of fun hacks. And when I read her blog it makes me happy to see someone with that joy of uncovering mysteries.

I just wanted to reply here with "You are my hero" . But someone beat me to it. I must subscribe now.

This also fires up my drive to get more into Radio's and radio astronomy. It so fun to be able to grab all that stuff from the air that most people are unaware of. I got my first handheld a while ago, and people were like "WOW amaze" when There was a really clear night in Budapest, Hungary with the ISS 70deg. overhead, and I was picking up Russian com while pointing to the illuminated station. ( -- yes unlicensed (but I don't TX) ). And now planning to get a license because more bands for the win, and licensed radio operators actually get much love from government and rescue services.

There's also lots of stuff that you can do with a cheap DVB-T tuner and simple (DIY) aerial.

Re: Mystery signal from a helicopter

#53

Post by jrockway »

EEGuy wrote: post #38
jrockway wrote: post #5

Earlier quoted context omitted.

Not really a hack. Subcarriers are how they added color to TV, stereo to FM radio, and so on. WWV/WWVH also sends machine-readable time codes at 100Hz like this.

>Subcarriers are how they added [...] stereo to FM radio... Set your time machine for 1958, or follow this link [0] to see how RCA did both FM stereo (throughout the article they call it "multiplex") and 67 KHz "SCA" subcarriers. Admire the awesome 5KW FM transmitter cabinetry and transformer shielding. [0] http://fmamradios.com/BTE-10B.html

One thing I find particularly interesting about articles from this time period is that Hz is not yet the name for 1/s, and so everything is in "cycles per second".

According to Wikipedia, the transition started in 1960, so we're two years away when this article was published.

Re: Mystery signal from a helicopter

#54

Post by graupel »

We operate news helicopters at TV stations around the US and they all use a similar system.

Basically the right channel of audio is typically the microphone from the pilot or reporter and the left channel is the audio feed transmitting what is basically modem data back with the GPS coordinates of the helicopter and some other data.

This data is used at the antenna site to track the helicopter and point the antenna in the correct direction to keep a line-of-site since the transmission system from the helicopter to the receiver is line of site (microwave) based.

It's really cool to sit and watch the receive antenna track and move responding to the movements of the helicopter miles and miles away.

The antenna is on the belly of the chopper here - http://www.imt-broadcast.com/super-pod?cat=Products

The receiver is generally centrally located on a tower - http://www.imt-broadcast.com/silhouette?cat=Products - it's a parabolic dish inside a radome like this.

Re: Mystery signal from a helicopter

#57

Post by wglb »

nl wrote: post #36

I love this: Several people in the restaurant were waiting for orders with their similar devices, which suggested to me this could be a pager system of some sort. Turning the receiver over, we see stickers with interesting information, including a UHF carrier frequency. For this kind of situations I often carry my RTL2832U-based television receiver dongle with me (the so-called rtl-sdr). I knew I was forgetting somet…

For this kind of situations I often carry my RTL2832U-based television receiver dongle with me

But of course.

Re: Mystery signal from a helicopter

#59

Post by lucb1e »

sitkack wrote: post #44
lucb1e wrote: post #18

Earlier quoted context omitted.

Been there, was cool indeed! If you aren't planning to already, you should come to the 31c3 :)

It is a certain commitment to Germany over Christmas.

It started the day after Christmas, though I did travel on second Christmas day. Totally worth it in my opinion. This was my first year and I can say that an extra day of that experience is always worth it.

Also WiFi totally rocked on day -1, but if you want that I guess you could also go wired any other day (symmetric gigabit and the best abuse policy in the world yay!).

But of course you can also travel on the day it starts and miss a few talks, it's up to you and your family how much of an issue it is to miss 2nd Christmas day. I was home in plenty of time for new year though, you still have that ;)

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