Hacker News Reader

Comment by _whiteCaps_ | Hacker News Reader

Be careful with SDR's. One minute you're scrolling around the spectrum, and the next you'll find yourself ordering parts for a 36 element Yagi and AZ/EL rotator, and a $3k radio to do Earth Moon Earth bounce communication.

View on HN

Literally me right now, got my first SDR less than a month ago because I wanted to have an FM radio for emergencies and I am designing antennas and studying for my amateur radio license.

Good luck with the license! There's lots of people on Mastodon that chat about radio stuff.

Thanks ! What accounts should I follow ?

Anyone on mastodon.radio, and check out the #amateurRadio topic.

> because I wanted to have an FM radio for emergencies

Just make sure you have batteries/a way to run it!

When we lost electricity for 1.5 day here last month (Spain), I thought I'd be clever and use my SDR too, but since we didn't have electricity at all, and none of my laptops were charged, I was out of luck. Wife's Macbook had battery available, but since I never used it with her Macbook, of course it didn't have the software/drivers needed, and the internet didn't work as all ISP equipment was also without electricity. Ended up listening to the radio in the car which was more than cumbersome :/

TLDR: get a shitty battery/hand-crank powered FM/AM radio for emergencies

Remember schematics for radios powered just by radio waves. No need for battery or hand-crank. That was in some old books, but never managed to build one.

I could be wrong but I think that only works for AM, not for FM.

supposedly you can demodulate FM with "slope detection", off tuning slightly so as the signal varies in and out of the resonance of the tuned circuit you can get an audio signal. Its gonna be mono lol. The "Q" of the tuned circuit needs to be pretty good and its interesting to see that they use copper tubing as the coil wire or more technically in the linked page, a resonator.

https://electronbunker.ca/eb/FMCrystalSet.html

That's AM crystal radio but there aren't that many AM stations left these days, most have been torn down because (thanks to AM) they need insane amounts of power to be receivable across larger distances.

Not in the USA. We still have 50,000 watt clear channel stations. On a clear winter night, local lore has it that WJR-760AM Detroit could be heard in Mexico. Crystal radios still work...well, not fine, but as good as they ever did. AM frequencies are low enough they skip off the ionosphere.

I remember a family road trip from Chicago to South Carolina in our '77 Impala wagon, when my whole family was listening to a DePaul basketball game on WBBM Chicago. My dad was a big fan. It was late at night, and the game came down to the last shot in the last second or so. The station was barely coming in, so we pulled over and heard DePaul win on a buzzer-beater... then the station blinked out. It was perfect.

I always think about this when I see another story about AM's demise.

> We still have 50,000 watt clear channel stations

On shortwave, we even have 250,000 W transmitters just blasting RF everywhere.

We call them flame throwers for a reason.

Mmm, I think you may have AM and FM reversed there. If I remember correctly, FM only goes 65 miles or so, but AM can go thousands of miles under the right conditions (at night, mostly).

If you want an FM radio for emergencies, get a battery-powered analogue FM radio, not a computer running SDR!

Packet radio, srsRAN, LoRA, Doppler Radar. So many fun things to do with SDR.

If anyone wants ideas, try and get on the WISPR network! All you need is like 20 ft of wire and an SDR and you can listen to signals from across the ocean easy.

WSPR, WISPR is something else.

https://www.rtl-sdr.com/a-tutorial-on-receiving-wspr-with-an...

Confirming this. Sounds like a joke but suddenly Ali knows just how how to snipe you with radio equipment offers...

I was already building a homelab, and was eyeing SDR and Meshtastic gear.

Don't do it!! Next you'll be setting up a weather station. Then you'll be setting up a microphone to ID birds via Merlin. Then home Assistant. Oh gosh it never ends.

But it's so much fun.

This comment is targeting me personally.

Well now I'm looking at automatic bird id and logging so I can track local species and see what my attempts to turn my stretch of grass into a wildlife garden does... Thanks, I think?

I'm so sorry. Lol

They are all ready on my to do list, but just those three things.

So far. While at it consider storing all the Linux isos ever existed too

I feel attacked.

What weather station did you end up with? And if it’s already been set up, is it proving to be more useful than local weather stations?

$3k is barely getting started. Literally barely getting started.

But you love it anyway

My buddy is one of the top station builders and contesters. He says it is a about $10,000 per tower. And one tower won't do.

The hell are those guys doing? I always had the itch, but never pulled the trigger on getting my feet wet into SDR. Radio astronomy?

It's a ham radio contest station. Doesn't really have to do with SDR.

https://www.youtube.com/watch?v=Dd4NWyFq-dM

Tim’s station is one of the biggest in the world. His tallest tower is 240 feet high.

Some stations do use SDRs to feed the reverse beacon site. https://beta.reversebeacon.net/main.php

One of the few hobbies in my adhd/ult life that has sucked me in and spat me out precisely as described

What’s ult?

adult with adhd I assume?

That makes sense, thanks. Ad[hd/ult].

I will avoid it for now because I don't think my wallet can handle it. I got really into home brewing for a while. Then synthesizers and drum machines. I need to stick to cheaper hobbies

And then there's the license upgrades!

Admiral Ackbar says... "It's a trap!"

... and time and money for acquiring a ham license!

Followed by more thousands of dollars for HF and 2m/70cm rigs, followed by more thousands of dollars for Hamnet links, a QO-100 sat dish for the Europeans...

You can do it on the cheap with CCRs and estate sales. My Kenwood HF unit was bought for $250, I made wire dipole antennas. I'm surrounded by Baofeng equipment as I type this. Total outlay for all of it probably on the order of $1000.

I do so want an Icom 7300, though.

I'm so jealous of the people that can see QO-100. Here I am in Canada checking my app for the birds to fly over, and people on the other side of the world can just point their antenna at it any time. :-/

Only 3K to bounce shit off the moon?

No... 3k just for the radio - actually, an IC-9700 is about $2k now.

Then add the yagi antenna, az/el moon tracker, amplifier, coax, etc. It really starts to add up.

I've never done this but I've worked a bunch of satellites and the ISS repeater. It's generally the same stuff, just a bit more powerful and precise.

Can be done more cheaply if tou are good at reusing things and building.

Can be cheaper than that. I picked up 2 used icoms for about $500. I haven't tried to moon bounce with it yet, but the one should be able to (and do satellites too). So the radio by itself would have been about $300 and the antennas are self built.

Reply on news.ycombinator.com