colanderman
Joined 18 years ago
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Member since
Oct 13
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Comment · 5 hours ago
Yes, I feel like there has been a sharp uptick in this the past couple months.
Whatever magic is built into the CloudFlare checkbox and my motion to click on it, I really wish was just part of the browser and my motion to click on everything else.
Comment · 27 days ago
This seems to assume that the segment between the pivot point (wrist or elbow) and the butt of the chisel must form a 90° angle with the chisel's shaft. Not being a woodworker – can't one simply move the wrist or elbow slightly higher (thus forming an obtuse angle) to compensate for the depth of the head to ensure that even with a flat mallet head strikes perpendicularly? So mallet head angle becomes purely an ergonomic adjustment to allow better arm placement.
Comment · 5 months ago
Anything physical which dampens higher frequency oscillations would act as an antialiasing filter.
Comment · 6 months ago
Spectral power density is the primary concern.
The legal power limit in these bands is 1 W. If you spread that out over 500 kHz, that signal is weaker than background noise at any given frequency for anyone more than about a city block away. (Give or take many factors.)
But, if you compress that 1 W into, say, 12.5 kHz (typical for FM voice), your signal is now detectable (and will interfere with other, possibly licensed, users) at over 6 times the distance.
There are probably other factors. For example, it's not legally sufficient to simply reduce your power by a corresponding factor. I suspect it may simply be the FCC's goal to reduce conflict between users by mandating spread-spectrum technologies for unlicensed use.
Note also that 47 CFR 15.247(e) [1] gives a spectral power limit which corresponds approximately with the 1 W max / 500 kHz min specified in (b)(3) and (a)(2).
Final side note – https://docs.fcc.gov/public/attachments/FCC-02-151A1.pdf is interesting reading as to how the current form of 15.247 came to be. Specifically it changed the rule from specifically DSSS to digital modulation generally, which in turn allowed the transition from 802.11b (DSSS) to 802.11g (OFDM) on 2.4 GHz.
[1] https://www.ecfr.gov/current/title-47/part-15/section-15.247...
Comment · 6 months ago
Correct. The LoRa configurations mentioned which offer 100× the speed of Meshtastic/Core operate at 800 kHz and 1.6 MHz bandwidth, which are permitted by the FCC in 15.247.
As far as I know there's not actually anything particular to 2.4 GHz allowing higher throughput for LoRa than that the corresponding Semtech chip happens to support wider bandwidths. (I.e. no legal barrier.)
The tradeoff is less range due to lower link budget. Doubly so because 2.4 GHz has higher free-space path loss. You're not going to get outside your house with these speeds. The primary use (as stated in the original post) is likely through clear space with a directed antenna.
(The 2.4 GHz band is better suited to this use since you can use antennas with higher than 6 dBi gain. If my math is correct, anything higher than 11 dBi is a win even accounting for FSPL and the power derating the FCC imposes.)
(Aside, I am the author of that MeshCore ticket.)
Comment · 6 months ago
The 915 MHz, 2.4 GHz and 5.8 GHz bands are regulated in the US largely in the same manner, see https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A...
Comment · 6 months ago
I did not state that humans cannot see corona.
Nor is the paper is about humans seeing corona.
It is about detecting UV photons using specialized equipment.
Comment · 6 months ago
Which photograph? The one in the article is not from the paper. The paper contains no photographs of corona.
Comment · 6 months ago
Can you point me to the images of corona in the paper which I missed?
Comment · 6 months ago
The images in the article are not from the paper. The paper contains no images of corona.
Comment · 6 months ago
There is in fact no photograph of treetops glowing.
There is a digital UV-wavelength video of the corona, and a visible-wavelength video of the trees.
The paper [1] contains a sole picture with tiny circles indicating where the UV-video detected corona events, overlaid over a frame of the visible-wavelength video.
The paper does also contain a video [2] which overlays a somewhat processed version of the UV video over the visible wavelength video, where UV photon events are indicated by decaying red dots.
[1] https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL11...
[2] https://agupubs.onlinelibrary.wiley.com/action/downloadSuppl...
Comment · 8 months ago
Nice! I've been looking for such a thing lately. KISSLoraTNC [1] is another implementation: The radio control interfaces differ though.
Comment · 8 months ago
I am just getting into the packet scene in the Boston area.
APRS aside, as far as I've found, there are about a half dozen Winlink nodes in the area and one BBS. And one lovely node in Cambridge (KZ2X-1 [1]) which provides connectivity to a bevy of ancient (though virtualized) OSes.
I don't know how much AMPRnet activity there is. There are only 7 allocations in the area (mine included). I'd love to be able to e.g. log in to my home network from a few radio hops away but I don't think there's any infrastructure in place for that (such as Mobile IP).
Comment · 8 months ago
Hah! I was literally about to open up my nascent userland AX.25 stack. Is yours open-source, or would you mind sharing? (My e-mail is in my profile.) I want to get something running on an ESP32-S3. My goal is to turn a Cardputer into a companion TNC console for my Kenwood TH-D74.