Transmitting software via TV audio / Prestel information system - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: February 04, 2018, 05:50:37 am
content: (Fast forward to the end for the BBC Micro code)

author: Ampera
author_rank: Super Contributor
timestamp: February 04, 2018, 07:06:48 am
content: I tried just for kicks decoding the Bell 103 signal. I got something, but for all I know it's garbage data, and not much of it. If it is correct data, then it's not intended for any character set I know of. I used minimodem and it seemed to be able to get everything. here is the data:https://pastebin.com/Bacbs64zIt's possible, infact quite likely, this data is just garbage. It's definitely Bell 103, but the over abundance of repeating bytes, and multiple 0xFF bytes, I don't think this is anything useful. Perhaps some other suggestions on how to use minimodem better, but other than that, I have nothing else.Neat concept though, reminds me of Datablast, as covered by Tom Scott.

author: stevelup
author_rank: Regular Contributor
timestamp: February 04, 2018, 12:33:42 pm
content: The audio at the end of that clip is this...beebwiki.mdfs.net/Acorn_cassette_format

author: Ampera
author_rank: Super Contributor
timestamp: February 04, 2018, 03:26:29 pm
content: Ah, that would make more sense. I was thrown off by the use of the Bell 103 modem in the video. It's interesting that I wasn't far off, I wonder if the data I collected is in any way still useful, as it's still just a 300bps connection using a mark and space tone that the program can probably decode.

author: Ampera
author_rank: Super Contributor
timestamp: February 04, 2018, 04:42:09 pm
content: Well I tried to convert the audio recorded to a .uef file for loading in BeebEm, but unfortunately I wasn't able to get it to work. I use MakeUEF, and it didn't function.

author: SeanB
author_rank: Super Contributor
timestamp: February 04, 2018, 05:31:16 pm
content: I used to use Prestel's clone here, but after a while the only use I had for it was because there was a page with an X400 gateway to the Internet.......... Made sense at the time, as then dial up connections to Beltel were a toll free number, and they only charged you 2c per minute for connect time.Later on I got a higher speed modem ( a whole 33.6k, later on a dizzying 56k networked locked one, which would invariably die after 6 months and need replacement), that is still around, but those used a regular call rate, so I paid for the then brand new, never before seen, Callmore Package, which meant that any call after hours, or after 5PM on Friday till 7AM Monday, were charged at a flat fixed cost of up to R7 ( currently 50c US) provided you did not disconnect. Friday 17H05 phone went off hook and on line till Monday morning 06H45 and i would download over the speedy 56k link.I even got 56k out of it consistently after replacing every socket and cleaning them, and going into the phone cabinets and tightening all the screw block links for my line to get a good clean noise free line. Was even better after the telco came around and replaced all the 80 year old lead sheathed paper cabling, though I still had the 375m long 250 pair main trunk in oiled paper sheathed copper, thankfully none of the horrid aluminium phone line that is used in places.Now have DSL, and did the same for the connections, got an extra 3dB of SNR out of it doing that and terminating into an old Krone box and 10 pair strip, and a dedicated DSL filter right there so there are no stubs in the line.

author: steve30
author_rank: Frequent Contributor
timestamp: February 27, 2018, 01:04:14 pm
content: In case anyone reads this topic and wonders about the software transmission, I loaded it up on my BBC last year.Seehttps://www.eevblog.com/forum/chat/how-to-send-an-'e-mail'-1984/