Show HN：一款讓電腦接駁電話線的 USB-C LTE 數據機

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Show HN: A USB-C LTE modem that gives my computer a phone line (github.com/koppar-ai) 22 points by abijahkaj4 hours ago | hide | past | favorite | 9 comments help Vaushite32 minutes ago | next[–] Obviously AI vibed, which means the project probably has never been built and wouldn't work if you built it. reply abijahkaj21 minutes ago | parent | next[–] I mentioned in the top comment that Koppar generated the board and that the first batch is about to be ordered, so no detective work needed there. I'm just as skeptical of blind AI hardware output as you are, which is why I audited every net against the datasheets and put all the flaws in REVIEW.md in the repo before ordering: - The 0.33 mm RF trace came out to ~35 Ω instead of 50 Ω and hopped layers through vias (I included Pi-matching pads to tune it on the bench). - The 3.8 V buck converter was placed too far from its inductor, and the 1.37 mm power trace is narrower than Quectel's 2 mm recommendation (~100 mV drop at 3 A). - The SIM socket (J2) is oriented inward, which is annoying mechanically. 5 bare boards + 2 PCBA units are currently being ordered at JLCPCB, and I'll order the EC25-EUX modules separately to hand-solder onto U8 since JLC was out of stock. Since the KiCad files are in the repo, if you spot a specific net or pinout error that will brick bring-up, let me know so I can bodge-wire it next week. reply drum557 minutes ago | root | parent | next[–] The PCB looks super weird, what is going on here? https://files.catbox.moe/nijoin.png https://files.catbox.moe/suazr4.png They sort of look sensible until you look closer and then the whole board is fever dream autorouting. reply mycall2 hours ago | prev | next[–] Will LTE continue to work when 6G rolls out in 3 years? reply wolrah14 minutes ago | parent | next[–] > Will LTE continue to work when 6G rolls out in 3 years? A significant change that came with LTE is the use of OFDM as the base of the air interface, which means that cellular providers no longer need to allocate large segments of spectrum to one protocol or another. Towers that were upgraded from 4G to 5G didn't need to disable 4G or consistently split their spectrum between the two they way they did when upgrading from 2G to 3G or 3G to 4G, they can dynamically allocate subchannels in each mode based on the immediate needs of their users. It seems unlikely that whatever technologies come in the future will regress in this way, so there shouldn't be a need for a hard cutoff at any point and I'd expect LTE devices to keep working for many generations to come. reply j4532 minutes ago | parent | prev | next[–] Probably for a while - lots of IoT uses it, especially with the push away from 3G. reply abijahkaj4 hours ago | prev[–] I wanted a real phone line on my computer: calls and texts on a physical SIM, answered through my headset at my desk, or by a script or an AI agent when I'm away. Cloud numbers get treated as VoIP, and old Android phones give you no clean way to get call audio in and out over USB. So this is a 4-layer USB-C board around a Quectel EC25-EUX. Behind a USB hub, the computer sees an LTE network adapter, the modem's AT serial ports (caller ID, SMS, answer), and an RP2040 acting as a USB sound card. The RP2040 bridges the modem's 1.8 V PCM audio through a level shifter. There's a 3.8 V buck sized for the 2 A GSM bursts, and no battery. I wrote the spec as one page of text, and Koppar, the tool I'm building, generated the schematic and the board. Then I reviewed it against the datasheets. The review found a 35 Ω antenna feed that hopped layers, a buck 60 mm from its inductor, and a SIM socket facing into the board. The parts matching would have bought an 18 µH inductor for a 4.7 µH slot. REVIEW.md in the repo has all of it with the numbers. Status: the boards aren't built yet. The repo is the design as I'm ordering it: KiCad 10 project, Gerbers, JLCPCB BOM and placement files. Bring-up and the sound-card firmware come next. Happy to answer anything about the audio path or the power design, and I'd like to hear what you'd change before the first bring-up. reply j4531 minutes ago | parent[–] I believe there are VOIP phones that are sim card based. Imagine a country that doesn't have land lines but folks want a home phone. reply wolrah9 minutes ago | root | parent[–] There are SIP to cellular gateways which have historically been very popular in regions where landline to mobile calls cost money but mobile to mobile do not, but they mostly don't exist in the US market other than high-density devices mostly used by SMS spammers. The only actual VoIP phone with a SIM card I'm aware of is the Yealink T74LTE which for a long time was exclusive to Verizon's business phone service but has recently become available for general purchase, those can support both SIM over LTE data and VoLTE (which is also basically SIP but over a prioritized channel). reply Consider applying for YC's Winter 2027 batch! 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