words per minute confusion

Thread Starter

bhuvanesh

Joined Aug 10, 2013
268
Transatlantic cable in 1880's can transfer 8 words per minute(approx 5bps per second)

I have seen this in video. In general does the the word have any specific bits or the bits of the word change accordingly
 

Thread Starter

bhuvanesh

Joined Aug 10, 2013
268
Each letter need 8 bits so word paris need 40 bits.So 8 word per minute mean 320 bits per minute(5bps per sec) ,right?
 

MrChips

Joined Oct 2, 2009
30,701
Back then Morse code would have been used for transmission.
paris .--. .- .-. .. ... works out to about 5bps if the speed is 8 words per minute.
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
Back in my military days when trained in Morse, one had to qualify send/receive at so many words/min, these were blocks of 5 of random characters.
This also co-coincided with classified security encoded messages which were formatted in the same 5 char blocks.
Max.
 

alfacliff

Joined Dec 13, 2013
2,458
I used to listen in as they trained in morse. knowing morse due to having earned a ham liscense before going into the army helped a lot. I had a 1st class commercial liscense then too, so I got to work on transmitters I had not trained on. made life more interesting.
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
I had to work occasionally to the civilian professionals, Cable & Wireless Co etc, I had to send QRS a few times as these guys were used to 35+ words a Min.
Incidentally I was on a Radio training exercise on the edge of the Libyan Desert when the WW11 B24 Liberator, 'Lady be Good' was found after being lost during WW11 so I got to report that back to HQ.
Max.
 

alfacliff

Joined Dec 13, 2013
2,458
baudot is a 5 bit code used by older teletype systems. the standard was so people could be charged for number of words sent in the old days.
 

Papabravo

Joined Feb 24, 2006
21,157
Amateur Radio Operators still use Baudot code for RTTY (Radio Teletype) communications at either 45.45 baud or 75 baud. MMTTY is a freeware package for decoding and generating RTTY as either AFSK (Audio Frequency Shift Keying) or FSK (Frequency Shift Keying). You don't even need a radio. You can record the audio output and then decode the playback. Probably wouldn't fool the NSA for long though.
 

nsaspook

Joined Aug 27, 2009
13,079
You can record the audio output and then decode the playback. Probably wouldn't fool the NSA for long though.
No it won't, most of us old Navy radio guys could tell what it was in a instant and decode just about any possible RTTY signal using gear from the stone age.

One of my favorites, we could send 8 (encrypted) tty channels on one voice audio channel
http://www.virhistory.com/navy/rtty-mux-ucc1.htm

75 baud, 100wpm.
https://www.youtube.com/watch?v=ZI2vr4jM60E
It seemed pretty fast back then. :D
 

alfacliff

Joined Dec 13, 2013
2,458
I use digpan, has quite a few of the digital modes. the newer pc sound card programs are real easy to use, and the filtering built into the sound boards makes copy real easy with noise. by the way, they also transmit or send out the tones.
 

KL7AJ

Joined Nov 4, 2008
2,229
Transatlantic cable in 1880's can transfer 8 words per minute(approx 5bps per second)

I have seen this in video. In general does the the word have any specific bits or the bits of the word change accordingly
They were using Morse Code, which has ABOUT 4 bits per character on the average. Dash is three times the length of a dot with "correct" morse code.
 

MMcLaren

Joined Feb 14, 2010
861
A late reply, but hopefully informative...

Regards, Mike

Rich (BB code):
;
; Some general information about Morse Code Speed;
;
; <1> A Dash is three times longer than a Dot
; <2> A Dot space is used between Dashes and Dots within a character
; <3> A pause between characters is three Dots long
; <4> A pause between words is seven dots long
;
; The word 'Paris' was established as an international standard
; for calculating the speed of Morse in words-per-minute (wpm)
; and characters-per-minute (cpm)...  This works out to 50 dots
; (or dot times) per word and yields the following timing;
;
;  5-wpm ( 25-cpm) =  60 /  250 dots = 240-msec / dot
;  6-wpm ( 30-cpm) =  60 /  300 dots = 200-msec / dot
;  7-wpm ( 35-cpm) =  60 /  350 dots = 171-msec / dot
;  8-wpm ( 40-cpm) =  60 /  400 dots = 150-msec / dot
;  9-wpm ( 45-cpm) =  60 /  450 dots = 133-msec / dot
; 10-wpm ( 50-cpm) =  60 /  500 dots = 120-msec / dot
; 15-wpm ( 75-cpm) =  60 /  750 dots =  80-msec / dot
; 20-wpm (100-cpm) =  60 / 1000 dots =  60-msec / dot
; 25-wpm (125-cpm) =  60 / 1250 dots =  48-msec / dot
; 30-wpm (150-cpm) =  60 / 1500 dots =  40-msec / dot
; 35-wpm (175-cpm) =  60 / 1750 dots =  34-msec / dot
; 40-wpm (200-cpm) =  60 / 2000 dots =  30-msec / dot
; 50-wpm (250-cpm) =  60 / 2500 dots =  24-msec / dot
;
 

alfacliff

Joined Dec 13, 2013
2,458
the transatlantic cables were slow due to capacitance of the cable to ground. thats hundreds of iles of wire surrounded by conductive salt water. I found a story that during development, someone decided on 10,000 volts on the wire. it worked for a day befror burning out. the did better the next time.
 
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