[dekhn]

My grampa was a ham radio guy and he told me a lot of things. I was really amazed by shortwave and how radio could travel long distances by bouncing off the ionosphere. He also gave me a shortwave radio and I remember tuning into weird stations that would just say numbers in a funny voice ("numbers stations"). He even had a ham radio in his car and could dial phone numbers remotely through it.

I never really got into ham, I'm still not much of a radio person (I prefer wired) but I still had fun playing with RTL-SDR; listening to my car's tire pressure monitors and various other things in the ISM band. Antennas are still fairly spooky magic to me, though.

[Taniwha]

I was a radio ham in the early 70s used to hang out with some guys who were snarfing weather satellite data - essentially it worked this way - the satellites passed over and either spun along their axis or had a spinning sensor - that made a continual FSK signal (think a FAX signal, because it was intended to be downlinked to actual early fax machines) - we'd calculate the pass time and grab it on a big yagi steerwd manually (by listening to the noise floor).

In a dark room it would be played onto a TV screen with a very slow horizontal rate, vertical retrace would be done manually with a switch and the vertical increments were extracted form the signal. In front of the TV we'd place a bunch of cameras, we'd open the shutter at the start of the pass and close them at the end. At the end of the night we'd develop the film - the meteorology people who'd paid hundreds of thousands of $$ for ground stations were pissed that we were getting better quality images than their fax machines.

Also around midniught local time (in NZ) we'd pick up processed world images - 4 around each pole and 4 around the equator, with the country boundaries overlaid, and the communist countries carefully whited out

[wkat4242]

Why were those whited out I wonder? It was just really lowres weather info.

I mean, today you can even see north Korea on Google maps :)

[Taniwha]

Yup it was really lo-res - it was the 70s the cold war was in full force - those screens were being put together by what at the time was called a 'super computer' probably not as powerful as your phone

[geocar]

The tire radio was surprising! I was looking for my pool sensor when I found my neighbours car. Then I told my neighbour that his car told me his tire pressure was low and he said he had no idea his car was literally broadcasting what his tire pressure is (and serial numbers and so on…)

[stevekemp]

For me too. I setup a couple of wireless 433Mhz temperature/humidity sensors in my flat (one on the balcony, one on the sauna).

Turns out the balcony sensor was just that little bit too far away to be regularly detected. However I noticed that I could get temperature readings from the car-tyres parked in the carpark to the side of my flat.

So I switched to using those instead for my "outdoor" temperature. Works a little better than my balcony would have done, as that is glazed and warmer than the actual outdoor temperature.

[themodelplumber]

Numbers stations are still pretty fun. Here's a video I got of the Cuban one, which is relatively easy to pick up in the US:

https://twitter.com/systematikk/status/1072960631916027904

Last I checked, they were using Windows XP freeware for data encryption.

There's also the shortwave radiogram and other interesting stuff if you go deep. The portable receivers and straight up SDRs they sell these days are pretty amazing in terms of sheer availability.

This receiver has been fun to use on the go:

https://www.youtube.com/watch?v=j3WQQn7rM3k

And the more consumer receiver stuff is now starting to ship with remote app control as well. A pretty awesome time for radio really.

[wkat4242]

I'm surprised numbers stations are still a thing. Back in the cold war every serious traveler carried a world band receiver. But these days carrying such equipment would draw attention, most world stations have even been decommissioned.