On Wednesday 10 September 2025 22:11:16 gene heskett via tde-users wrote: > On 9/10/25 23:12, William Morder via tde-users wrote: > > On Wednesday 10 September 2025 18:47:24 dep via tde-users wrote: > >> A long day and night with Commodore OS, in case anyone's interested. > >> > >> Maybe somebody else out there who knows more about these things > >> (thinking of you, Gene!) might be able to tell me why this cannot > >> possibly work. > >> > >> Bill > > Yes it /could/ work, Bill, but introducing the noisy world of broadcast > does entail an attention to detail involving frequency accuracy and some > sort of an error correcting algorithm where sufficient redundancy exits > in the code format to make self correcting code practical. Fire coding > comes to mind, but even that requires sufficient redundancy to fix multi > bit errors created by a leaky crossbar on a power pole. A pole > originally equipt with 2400 volt rated glass insulators, up-graded to > carry 7200 volts w/o replacing the insulators, compounded by the > diagonal steel braces holding the crossbar level but with the center > bolt into the pole not having been re torqued since it was originally > bolted up in 2400 volt REA days. There does not exist in this scenario, > a method to demand a re-transmission of corrupted data. All the common > methods today, rzsz, tcp, probably a dozen other's, all work because its > a 2 way path. Corruption detection is easily done with a crc on each > sectors (256/512) worth of data, but w/o the on demand retransmission, > is hellishly difficult. Yes, that case IS 2 way. But the speed of light > time delay doesn't make it easily done. Our voyager satellites are > delivering only femtowatts of signal at goldstone, so I expect half of > the available bandwidth is devoted to error detection & correction. At > that power level, I'd be amazed if they are functioning at over 1 bit > per second. Their plutonium thermally generated power is nearing the > end, and it will take electronic magic to get data from them in another > decade. And one hell of a budget item for boiling helium to maintain the > half degree kelvin the electronics at the focal point of the goldstone > dishes need to be able to hear the voyagers in the face of that half > degree of thermal noise. It's all we got in this case. > > > Cheers, Gene Heskett, CET. I knew you would be able to give me the long answer with technical details about radio's limitations. I will have to read this again later, when I am more awake. (This email is one of those "woke up in the middle of the night" replies.) Also, as I said, I have a shortwave receiver, and the idea of transmitting data over shortwave is what got my attention. If shortwave, why not other parts of the spectrum? Why not radio itself? Anyway, I will have to look into this a bit more. As I said in another reply to Andrew, just a few minutes before, I conceive of this as a kind of backup plan for internet access, in emergency situations, for example, or when one finds onself in a remote place without the usual ways of connecting; just to be able to send and receive emails or text, or to use a text-only browser, could be a lifesaver in extreme circumstances. Bill ____________________________________________________ tde-users mailing list -- users@xxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxx Web mail archive available at https://mail.trinitydesktop.org/mailman3/hyperkitty/list/users@xxxxxxxxxxxxxxxxxx
