Show HN: Record and share police/fire radio systems

Are you using polyphase channelizer now, as opposed to individual XFIR tuners? If so, does that still provide better performance given sparsely occupied channels?

There is also this Rust based P25 decoder that I have been wanting to give a try: https://github.com/kchmck/p25rx It is a ground up re-write that doesn't need Gnuradio, so it could be pretty efficient.

Banana Pi Zero? What board is that? (I've been experimenting with various board for a project, so genuinely interested if this isn't a typo)

Would love to know more about OTA ATSC on Raspberry/Banana Pi -- everything I read tends to say that these ARM-based boards are good for playback only.

Thanks a lot for the recommendation! I got the NooElec NESDR SMArt and it's working perfectly! Now to build my own antenna.

OK. I'll get in touch via email. Thanks for the offer!

Actually sdrtrunk does claim to support multiple dongles, though I have not verified the functionality. I tried it with an Airspy (10 MHz BW) so I did not need the multiple SDR support.

Are you saying 6 is all you need for most locales? Or that is the case in your area?

During network programming, act on subaudible cue tones. Sometimes the affiliate relays will let a little bit of a tone leak before acting, and you can use the same cue. If someone's driving the bus by hand, you'll definitely hear them. This will serve you well during football games to remove local commercials, at least, though increasingly local breaks come with a 120+ network avail before the tones fire and the affiliate takes over, so your training would still be useful.

When you hear "after these words from your local station," watch for < 100 Hz tones. They're high amplitude and you won't be able to miss them; VU meters will often peg hard right during a tone, depending on the network. Should be a tone out and a tone in, and it is modulated so it'll be quite apparent.

Another helpful avenue to explore would be in-stream RDS metadata, if you're working with typical FM. It lags a bit, but if you buffer a minute back or so you can look for transitions when the RDS data changes. Then you can use the same trick a delay uses to backfill its own buffer, and pad silences to restore your buffer. You don't care about dead air in your application, so you can be more aggressive than broadcast equipment can. (Talk radio runs >30sec behind, usually, and the "dump" button on a delay flushes the entire buffer, synchronizing air and program. It'll then slightly extend silences to get air "behind" program again. It has a little screen on it indicating how far back it is, and it's cool to watch it zoom back when people stop talking. If you hear a station dump delay, you'll notice they won't take callers for a couple minutes; this is why.[0])

Teach your setup to listen for EAS tones and you're well on the way to a startup of some kind. I think this was attempted in the past, actually...

[0]: https://en.wikipedia.org/wiki/Broadcast_delay#Computerized_d...

Wow. I used to cut, and occasionally write, radio spots for a living. I agree that it's annoying, but it's so that the message is carried across, not because marketing people are some epithet. That's what the sponsor is paying for, after all, and you are not. Radio-friendly music is often mastered with the same dynamics removed. Most pop and modern rock looks about the same on a spectro as the spots I used to cut. We made a conscious effort at my last station to master stingers ("you're listening to...") and other meta stuff at the same overall loudness level as the average spot, so there was a heavy contrast between the talk radio portion and the everything else portion and you'd have a solid cue of when to turn down if you so chose. There's actually pushes in the industry right now to move toward PPM meters that more effectively indicate loudness. We got it, believe me.

Radio is a lovely profession full of wonderful people. There is a strong hacker culture on the engineering and air operations side of things, and the head of sales at my last station baked six huge cakes for a company event in her home. Pretty much every day the station smelled like solder from some hilarious contraption the bored engineers were putting together. Most people who like HN would love a radio station.

Marketing ("sales," in radio) is a necessary function in capitalism, and loud commercials have nothing to do with ethics. If you want an example of how ethical radio sales can be, if I technically erred while airing even one second of a :30, they'd refund the whole spot and re-air it. Most of my job during broadcast operations was notating these exact problems, and they never thought twice about making it right. Why would they? Advertisers are what, you know, feeds the family of everybody at the station and gives you something to listen to on your drive home for free, and they do spot check.

This comment is just really, really awful all around, and I expect better from you. Ethical is not an antonym for crappy, nor annoying, and accusing a whole group of people of being unpleasant and unethical simply because [issue] is nothing short of completely shitty, speaking more about you than them.