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Author Topic: Width of CW Dot  (Read 724 times)
HA6SST
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Posts: 110




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« on: September 10, 2007, 09:44:48 AM »

I'm trying to resolve a timing issue in a transceiver transmit/receive circuit. Please could someone give me the width of a dot in milliseconds for the following speeds:

5 wpm
10 wpm
15 wpm
20 wpm
25 wpm

There's no point giving me the width for speeds faster than this because I struggle to hit 20 wpm. I am therefore  going to set the speed control for a maximum of 25 wpm.

HA6SST
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KB1OOO
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Posts: 214


WWW

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« Reply #1 on: September 10, 2007, 10:02:53 AM »


A word is 50 "elements", i.e. the number of elements in the word PARIS.  Dot is 1 element, dash is 3 elements, between character spacing is 1 element, and between word spacing is 7 elements.

So formula for 1 element (dot) in ms is

  60000
--------
wpm * 50

Here's a reference if you want to read more:

http://www.ac6v.com/morseaids.htm

73,
Marc
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KB1OOO
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« Reply #2 on: September 11, 2007, 05:56:00 AM »

just a correction on my description: *intra* char spacing is 1 elment and between character spacing is 3 elements.

Marc
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WQ3T
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Posts: 209




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« Reply #3 on: September 11, 2007, 08:34:44 AM »

I timed my dit on my oscilloscope at 62 mS with keyer set at 20 WPM. I haven't tried other speeds.
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KB1OOO
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« Reply #4 on: September 11, 2007, 10:53:44 AM »

Is it too difficult to plug into the forumla, which reduces to

1200
-----
wpm

and gives:

5wpm   ->    240ms
10wpm ->    120ms
15wpm ->      80ms
20wpm ->      60ms
25wpm ->      48ms
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WQ3T
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Posts: 209




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« Reply #5 on: September 11, 2007, 11:44:35 AM »

I suppose you always trust cash registers to figure your correct change also. I figure the change in my head and tell the cashier how much change I need. Then when the cash register displays the same amount, I say, "The cash register is correct". My 62 mS timing was something I measured myself, not depending on someone else's formula. I think the formula is off by 2 mS. Can you prove otherwise?
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KE3WD
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Posts: 5689




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« Reply #6 on: September 11, 2007, 12:07:30 PM »

Like 2mS differential is consequential...
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HA6SST
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Posts: 110




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« Reply #7 on: September 11, 2007, 02:09:37 PM »

Thank you for all the replies. A formula of 1200/wpm is easy to remember, all I need to do now is cure my problem of a shortened first dot when the transceiver changes over.

On with the struggle!!

HA6SST
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KB1OOO
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« Reply #8 on: September 11, 2007, 08:20:20 PM »

Sorry, I didn't mean to come off as a jerk.  I just wasn't understanding why my original post wasn't clear.

Marc
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WQ3T
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Posts: 209




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« Reply #9 on: September 12, 2007, 10:40:59 AM »

You did reduce the fraction to make it simpler to use. I haven't seen any jerks- just guys helping out each other.
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KE3WD
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Posts: 5689




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« Reply #10 on: September 12, 2007, 11:00:31 AM »

>>by HA6SST on September 11, 2007  

"Thank you for all the replies. A formula of 1200/wpm is easy to remember, all I need to do now is cure my problem of a shortened first dot when the transceiver changes over."<<

You might want to take a look at QST magazine tests, both for your rig and others, before you drive yourself crazy here.  

That first dit length is indeed problematic for many, if not most rigs.  

QST typically publishes an oscilloscope graph of the first dit element length for every rig tested.  

Almost all of them are shortened to some extent.  

Another test where TenTec and Elecraft transceivers often come out doing better, just another reason that they are loved by serious CW ops I guess.


--KE3WD
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KE3WD
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Posts: 5689




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« Reply #11 on: September 12, 2007, 11:05:03 AM »

BTW -- Shortened first dit in QSK will likely not be a problem at all with the speeds listed here.  

Somewhere up past the 30WPM mark would be when the shortened dit can start proving problematic.  


!
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W8ZNX
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Posts: 1




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« Reply #12 on: September 12, 2007, 03:57:27 PM »

im with KE3DW
shortend dit should not be a prob
most ops don't even notice it

if you rig does have a huge shortend
dit prob on qsk
how is it when you slow down
rx tx change over

lots of ops use the qsk mode
but do not realy run qsk style
so a slower longer change over
might work for you
with out having to mess with your rig

by the way what kind of radio is it

also you might want to ask
on the/your rigs user group
and there is a yahoo user group brasspounders

my FT 102 has a chirp
on first note after change over
i just turned up the vox delay
so it does not change over till
i turn it over to the other station

for qsk work
i have a old Ten Tec Omni D


yours truly
Mac

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W8ZNX
Member

Posts: 1




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« Reply #13 on: September 12, 2007, 03:59:18 PM »

KE3WD not KE3DW
mac
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KE3WD
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Posts: 5689




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« Reply #14 on: September 12, 2007, 06:07:01 PM »

That's okay, Macs are allowed to make typos.  

;-)


--Mac
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