Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 [2]   Go Down
  Print  
Author Topic: Pulse width of a CW signal?  (Read 10275 times)
LB3KB
Member

Posts: 234


WWW

Ignore
« Reply #15 on: March 27, 2012, 03:14:16 PM »

My point would be along the lines of what N3QE writes.  Morse code is not optimized for the letter frequency of (American) English, although it does better for English words than for random code groups.

The optimum lasted only through the first two letters (E & T), it breaks at I which has the same length as T.  And like N3QE says, O is way too long.  It is in fact just as long as X and Z.
« Last Edit: March 27, 2012, 03:19:11 PM by LB3KB » Logged
K5XH
Member

Posts: 3




Ignore
« Reply #16 on: April 03, 2012, 01:53:32 PM »

Simple answer from Google:

Based upon a 50 dot duration standard word such as PARIS, the time for one dot duration or one unit can be computed by the formula:

    T = 1200 / W

or

    T = 6000 / C

Where: T is the unit time, or dot duration, in milliseconds, W is the speed in wpm, and C is the speed in cpm.
Logged
K8AC
Member

Posts: 1478




Ignore
« Reply #17 on: April 29, 2012, 05:38:34 AM »

I can see why some folks are reluctant to ask questions!  The truth of the matter is that it would be difficult for anyone to answer your question without knowing a lot more about your CW signal.  For example, how is the weighting adjusted on the device that is generating the CW?  For academic purposes, I suppose one could assume a weighting that results in a dit being just as long as a space and a dah being three times that long.  But, having measured a lot of CW signals (mine and others), I can tell you that very few keyers are producing that ratio.  At least one high end transceiver produces dits and dahs that are substantially below the ideal ratio to the point of sounding clipped, when adjusted for a supposed perfect ratio.  So, the question that you think is so simple is not simple at all, at least it isn't if you are interested in any sort of accuracy.

73, K8AC
Logged
PA0BLAH
Member

Posts: 0




Ignore
« Reply #18 on: April 29, 2012, 06:56:47 AM »

I can see why some folks are reluctant to ask questions!  The truth of the matter is that it would be difficult for anyone to answer your question without knowing a lot more about your CW signal.  For example, how is the weighting adjusted on the device that is generating the CW?  For academic purposes, I suppose one could assume a weighting that results in a dit being just as long as a space and a dah being three times that long.  But, having measured a lot of CW signals (mine and others), I can tell you that very few keyers are producing that ratio.  At least one high end transceiver produces dits and dahs that are substantially below the ideal ratio to the point of sounding clipped, when adjusted for a supposed perfect ratio.  So, the question that you think is so simple is not simple at all, at least it isn't if you are interested in any sort of accuracy.

73, K8AC

Sure, but CW is CW and CW is 1 3 7 , anything else is not CW but distorted CW, euphemistically called "a fist"

The "high end transmitter" is designed for SSB hams, not able to transmit CW, (let it be receiving) but added as a sidekick just for sale or trading by the manufacturer, not for using by the owner, Or it may be to put a Begalli signed limited numbered edition highly polished sculpture  SPDT switch on it to impress other guys with a picture of the owner with his hands on it in the shack, planning to learn CW, whenever there is offered a course with success guaranteed or money back, with result and a graduation within a week, with a certificate on wall paper. THAT is ham radio nowadays. 27 MHz CB talking, with subjects of so minor importance that the public telephone and telegraph are not recommended by their CEO's for using them in order to transfer that kind of monkey talk.
73
Bob
« Last Edit: April 29, 2012, 07:17:01 AM by PA0BLAH » Logged
K8AC
Member

Posts: 1478




Ignore
« Reply #19 on: April 29, 2012, 02:17:40 PM »

To QRPNEW: I just set up a test to get an idea of the right answer to your question.  I used a K1EL WinKeyer USB, set for 50 WPM using their software, and I'm just assuming that their speed calibration is correct - could be off.  I then keyed one transceiver (Drake TR7) with the 50 WPM keyer while monitoring the signal on a second transceiver (Tentec Orion II) whose audio was being recorded by Adobe Audition software to allow me to look closely at the waveforms.  Running with a weighting of 50, which should result in an equal length of dit to space, dashes were observed to be 70 milliseconds long and dots were 23 milliseconds long - just about right. 

Someone else measuring the same thing would find that the numbers differ depending on a lot of things, such as waveform shaping in the transmitter or QSK performance.  For measurement purposes, I chose to start an element with the first indication of a rise from noise level and stopped the element length just before the level returns to zero.  In practice, the wave shaping in the transmitter affects the dot to space ratio a lot.  In my test, a visual inspection of the waveform would suggest that the keying was too "heavy", while in fact it sounded just right.  This particular transmitter was modified to eliminate key clicks and the resulting "long tail" is what affected the dot to space ratio. 

73, Floyd - K8AC
Logged
QRPNEW
Member

Posts: 51




Ignore
« Reply #20 on: May 12, 2012, 08:21:32 PM »

Thanks Floyd for going through all the trouble. The information was useful and precisely  what I wanted.

To QRPNEW: I just set up a test to get an idea of the right answer to your question.  I used a K1EL WinKeyer USB, set for 50 WPM using their software, and I'm just assuming that their speed calibration is correct - could be off.  I then keyed one transceiver (Drake TR7) with the 50 WPM keyer while monitoring the signal on a second transceiver (Tentec Orion II) whose audio was being recorded by Adobe Audition software to allow me to look closely at the waveforms.  Running with a weighting of 50, which should result in an equal length of dit to space, dashes were observed to be 70 milliseconds long and dots were 23 milliseconds long - just about right. 

Someone else measuring the same thing would find that the numbers differ depending on a lot of things, such as waveform shaping in the transmitter or QSK performance.  For measurement purposes, I chose to start an element with the first indication of a rise from noise level and stopped the element length just before the level returns to zero.  In practice, the wave shaping in the transmitter affects the dot to space ratio a lot.  In my test, a visual inspection of the waveform would suggest that the keying was too "heavy", while in fact it sounded just right.  This particular transmitter was modified to eliminate key clicks and the resulting "long tail" is what affected the dot to space ratio. 

73, Floyd - K8AC
Logged
Pages: Prev 1 [2]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!