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Comment by pavel_lishin | Hacker News Reader

I always assumed that space was noisy enough that things like wifi wouldn't work on the lunar surface.

If basic radio worked for talking between suits and the landing craft in '69, it surely shouldn't be a surprise that modern frequency-hopping, error corrected, wireless comms, with much more sensitive equipment would work well?

The walkie-talkie toys I had as a kid in the 90s had at least 10x the range of modern home wifi routers. Not to mention how far radio stations broadcast. I'm guessing that's the context they're working from.

That's because of different frequencies and power caps that are enforced by the FCC. If your WiFi broadcast with the same power, the frequency space would be unusable by your neighbors for their WiFi. The range of WiFi is very purposefully sabotaged to make it useful for more than just you.

And also because our kid-era walkie talkies were VHF (or at least mine were) which is a much lower frequency band than wifi. At a given power level, lower frequencies travel farther (i.e. around obstacles) but can't transfer as many bits as wifi.

I wonder how much power the wifi antenna on the cubesat is pumping out.

Assuming you are talking about FCC Part 15 regulations for 2.4 GHz, you couldn't be more wrong. There is no 'sabotage'

The EIRP is 4 watts in 2.4 GHz band. More than enough to wipe out your neighbors. Also more than enough to get absolutely tremendous range in line of sight conditions.

I can purchase and install an unlimited number of 2.4 GHz Part 15 devices, rendering the band useless to anyone so long as I am attempting to use those devices in a manner consistent with their application. As another Part 15 user, you have no recourse. If a licensed user complains to the FCC, they may decide I have to stop using them and notify me as such. Note: one of my neighbors does this, by having an AP on every 2.4 GHz and 5 GHz channel.

Newest Wifi 6 stuff in the US has a power limit on some spectrum and some usages, but nowhere near as low as what I was hoping for.

> Note: one of my neighbors does this, by having an AP on every 2.4 GHz and 5 GHz channel.

Sounds like a fun and ethical excuse to DOS some WIFI routers.

Why isn’t the limit 40 watts? Or 400? Why is there a limit at all?

You can pedantically criticize the use of the word “sabotage”, but then you’d be entirely missing the point.

400 watts would cause RF burns at 2.4 ghz.

And most people have a 1200 watt version in their kitchen for that exact purpose!

And all of that without an appreciable atmosphere to get in the way

Noise you can correct for with directional antennas, filters, and/or more signal processing voodoo. Meanwhile you benefit from space being actually empty - no pesky atmosphere in the way to attenuate signals (though also no layers to bounce the signal off), and no other transmitters in your area. Inverse square law works to your advantage in this context.

If you're above the frequency at which the ionosphere becomes reflective (around 30 MHz), why should space be noisier than the Earth's surface? Anything propagating there will reach down here (unless it's something really short wave absorbed by molecular bands in the atmosphere.)

In practice, it's going to be noiser down here, because of all the sources down here.

I don't know specifically about wifi but, check out EME bounces. With a hand held ham radio on the 6M band and a directional antenna made from like $6 of supplies from your local hardware store, you can have a radio that can bounce a signal off the moon and talk to someone on the other side of the earth.

It’s more like the 2m and 70cm bands, and really big expensive antennas. You can bounce signals off of meteor trails with a cheap antenna and 6m radios, though!

Been out of it awhile so i was thinking 6m, mighta gotten mixed with the scatter-e propagation. But I knew a guy down in San Diego who used to do EME bounces with cheap directional antennas he homemade. But that guy was also an EE at Qualcomm there.

But that was 6 years ago and since I've moved up to Oregon, I havnt gotten to do much ham stuff because I could never hit the repeaters around here. Maybe they are no longer up, maybe its all the hills and volcanic rock?

You can make it work with normal human antennas, as long as the other person has the big ones! I could never contact someone with the same antenna and radio as me via the MOON, but I can on certain days be heard by those big dogs!

Meteor scatter is pretty fun though!

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