CW rise time mod
Locked
12
12
Re: K3 CW rise time mod - Definition
 
|
Terms such as "tightening up key shaping" and "soft keying" and "hard
keying" are neither used nor defined in the latest issue of the Handbook. Worse, the latest handbook Figure 9.8 states that on-off transitions of the RF envelope should follow a sine-wave curve, so I don't quite know what to make of "DSP-generated raised-cosine key shaping." As to Goodman and Garmmer, I wouldn't be able to identify what is accurate and should be believed and what is inaccurate and should be ignored, so I don't think I'll go looking for those references. And no, Paul, I'm not trying to be a smart-ass here. I'm just a simpleton trying to decode the language used by people who know about such things. Pointing me to the Handbook -- which I should have had sense enough to do on my own -- did help in that it reminded me that key clicks and bandwidth are the issues associated with rise times and curve shapes, which is what I was really looking for, and Figure 9.9, if I study it long enough, may point me to a decision as to whether or not I want to modify ole #95. Either that, or wait for Al, VE1AWP, up the street with his FT1000 to complain about my signal when we both try to contest on the same band at the same time! Great radio and lots of good people around to help us understand it. Thanks, Paul. Gary, VE1RGB Paul Christensen wrote: >> I would like to see someone please take this discussion one step >> further and define the terms "hard" keying and "soft" keying, and >> describe how either an operator or someone listening would be able to >> discriminate between the two. > > Gary, this topic has been covered in great detail in nearly every ARRL > Handbook for at least the last fifty years -- as well as other > publications. Some of the most relevant material is covered in > articles during the '40s and '50s by By Goodman and George Garmmer. > Not all of the material pertaining to "optimum key-shaping" is > accurate, but otherwise, the content is still accurate. > > Many of us do not like to be held hostage to one rise/fall setting as > a "one size fits all" answer to our operating practices. With > DSP-generated raised-cosine key shaping, it's now possible to tighten > up key shaping at high CW speeds without appreciably consuming > additional bandwidth. > > Paul, W9AC Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3 CW rise time mod - Definition
|
|
In reply to this post by AC7AC
My questions about rise times, etc, was really really intended to
help me make a decision as to whether or not I wanted to incorporate the modification that started this discussion off. Your comments in the last paragraph make all kinds of sense and so off to the Elecraft Order Page I go. Thanks, Ron. Ron D'Eau Claire wrote: > (snip)... > Wayne plans to offer the ability to change the keying characteristic with a menu > setting. If so, the values he provides will assume all K3s have the same > hardware characteristics. If you don't have the recommended value for C222, > the results you get with various menu settings might be quite different than > expected. > > Ron AC7AC > > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
|
|
In reply to this post by Gary Bartlett VE1RGB
> ...Worse, the latest handbook Figure 9.8 states that on-off
> transitions of the RF envelope should follow a sine-wave curve, so I > don't quite know what to make of "DSP-generated raised-cosine key > shaping." Let me see if I can shed a glimmer of light here. A sine wave, going from 0 to 360 degrees (or 0 to 2 pi radians if you are of at persuasion), starts at 0, then builds to +1 at 90 degrees (pi/2 radians), dropping down to 0 again at 180 degrees (pi radians), then further dropping to -1 at 270 degrees (3 pi/2 radians) returning to 0 at 360 degrees (2 pi radians). OK, I'll stop the radians now :-) I suggest you sketch this on a sheet of paper to make it easier to follow along. A cosine is shifted by 90 degrees, starting at -1 for 0 degrees, building to +1 at 180 degrees, and dropping again to -1 at 360 degrees. The shape is the same. The cosine starts at its minimum value (-1) at 0 degrees while a sine wave is already halfway between its minimum (-1) and its maximum (+1) at 0 degrees. Our RF power can't go negative in the real world, so if we want to shape our keying, we must go from 0 to some positive value. One way to do this is to add 1 to the sine or cosine value. If we do this, the cosine goes from 0 at 0 degrees, to +2 at 180 degrees, then drops back to 0 at 360 degrees. The sine does the same, just offset. Adding 1 to the value makes it a "raised cosine" (or a "raised sine, if you want to talk about sines -- the wave *shape* is identical). Thus, "raised cosine shaping" and "follows a sine-wave curve" are two ways of saying essentially the same thing. Now, the reason we usually talk about a raised cosine is because we (or at least, I) like to start a wave generator at 0 degrees, and a cosine is conveniently at its lowest value at 0 degrees. Thus, to shape the CW waveform, the DSP starts a cosine generator at 0 and applies the result, offset by adding 1, to the RF envelope it is creating. AT 180 degrees, it stops. The RF waveform is at its maximum amplitude, the wave is properly shaped, and your adjacent channel neighbors are happy (or as happy as they're going to be!). The DSP can make this transition time be 5 ms - or 500 microseconds, or 10 seconds, or whatever it sis told to create. If you want to get a good visual look at all this, I highly recommend the paper by James Miller entitled "The Shape of Bits to Come." < URL:http://www.amsat.org/amsat/articles/g3ruh/108.html > If you read it, forget about PSK or FSK, and think about CW waveshaping. Also, remember that CW is traditionally decoded by ear, so any waveshape that requires you to look ahead in time (like the really narrow spectra he describes) would probably sound very odd by ear and would require that the dits and dahs being sent be delayed by 4 or 5 dot times. But it would make you a very good neighbor! 73, Lyle KK7P _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3 CW rise time mod - Definition
|
|
Lyle Johnson wrote:
> Let me see if I can shed a glimmer of light here. As usual, Lyle, a very useful and clearly written tutorial. Thanks! Bill W5WVO _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3 CW rise time mod - Definition
|
|
In reply to this post by Gary Bartlett VE1RGB
> Terms such as "tightening up key shaping" and "soft keying" and "hard
> keying" are neither used nor defined in the latest issue of the Handbook. My 1998 issue of the ARRL Handbook discusses the relevancy of "hard keying" on p. 15.7 and even uses that term to try and describe the effect. On the same page, reference is even made to the "crispness of keying." Perhaps, the latest editions have eliminated these ambiguous terms. Your initial request was the following: "I would like to see someone please take this discussion one step further and define the terms "hard" keying and "soft" keying, and describe how either an operator or someone listening would be able to discriminate between the two." The best way to address this is through actual listening to a keyed waveform that varies between 0 ms (i.e., a square wave), and a ramped wave with leading and trailing edges up to 10 ms. This can be easily done on some transceivers (e.g., TS-870S, IC-7800, and Omni VII) although the range may be limited from 2 ms. to perhaps 8 ms. One can listen to the keying on an external receiver while keying the transceiver and varying the wave shaping. In addition to the perceived effect of hard v. soft keying, the ARRL Handbooks tied-in the concept of "selective fading;" the ability to decipher the transmission in the presence of ionospheric changes and included a chart. That too may have been eliminated recently. Unfortunately, there's is no way to quantify or define subjective terms like "hard keying" any more than we can quantify a SSB transmission that sounds "bassy," "tinny," "compressed," or "distorted." Distortion can take on so many forms that the mere use of the word without further information is meaningless. Paul, W9AC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3 CW rise time mod - Definition
|
|
In reply to this post by KK7P
On Sunday 30 March 2008 01:56:46 pm Lyle Johnson wrote:
> A cosine is shifted by 90 degrees, starting at -1 for 0 degrees, > building to +1 at 180 degrees, and dropping again to -1 at 360 degrees. The cosine of zero is +1 and the cosine of 180 degrees is -1. Ian, G4ICV, AB2GR, K2 #4962 -- _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
|
|
>> A cosine is shifted by 90 degrees, starting at -1 for 0 degrees,
>> building to +1 at 180 degrees, and dropping again to -1 at 360 degrees. > > The cosine of zero is +1 and the cosine of 180 degrees is -1. Ah, I shoud've checked my math before I hit "send." Yes, you are correct. Lyle _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
|
|
In reply to this post by David Pratt-2
It's not that 3ms is a lot of time in terms of human scale. But, it is the
rise time of an electronic pulse. This can have a lot of impact on the transient waveform that results in an audio demodulator - i.e. receiver. The difference is noticeable enough to make the difference in a crowded band weak signal situation when the receiving station is differentiating what he hears. That's why a banjo sounds different than a guitar or violin. Al WA6VNN +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ In a message dated 3/29/2008 5:34:22 P.M. Pacific Daylight Time, [hidden email] writes: People, 8 ms.- 5 ms.= 3 ms., does it matter in any practical sense? I would really like to know who cares, and why? Can anyone hear the difference? Three-thousanths of a second? Not my old brain. 73, John, W2GW K3 #384 ----- Original Message ----- From: "Lyle Johnson" <[hidden email]> To: "Elecraft Reflector" <[hidden email]> Sent: Saturday, March 29, 2008 5:21 PM Subject: Re: [Elecraft] CW rise time mod >> Or do Rev A RF boards have a lower value for C222 than that shown on the >> schematic? > > Early production K3 RF boards have a 1 uF capacitor instead of a 0.1 uF > capacitor installed at C222. Yes, the published schematics show a 0.1 uF > capacitor. The effect of the larger capacitor is to increase the TX > waveform rise time to about 8 ms instead of 5 ms. > > Rev B RF boards have the correct 0.1 uF value installed. Sometime during > Rev A RF board production, the value installed on the board was changed > from 1 uF to 0.1 uF. > > Surface mount ceramic capacitors are not marked with a value, so you > cannot tell which you have by visual inspection. > > You can determine if you have a 1 uF rather than a 0.1 uF by: > > 1) Measuring the capacitance if you have a capacitance meter. > > 2) Looking at the Tx output RF envelope on an oscilloscope or "station > monitor" scope. If the fall time and the rise time look very similar in > duration, you have the 0.1 uF cap. If the rise time is about 50% longer > than the fall time, you have the 1 uF capacitor. You don't need an > oscilloscope with an accurate time base to make this comparative > measurement. If your oscilloscope has a low bandwidth (2 to 10 MHz), use > the 160 meter band. > > 3) If you are concerned that your unit may have the 1 uF capacitor and you > have no way to determine it otherwise, you can just replace it with the > 0.1 uF part and sleep better at night :-) > > If you don't change it, you will not damage anything. Your K3 will just > have slightly softer keying and an upcoming firmware adjustment of the > keying time will be less accurate. > > 73, > > Lyle KK7P > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com **************Create a Home Theater Like the Pros. Watch the video on AOL Home. (http://home.aol.com/diy/home-improvement-eric-stromer?video=15&ncid=aolhom00030000000001) _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
|
|
Hi everyone:
I have Thunderbird check for the magic characters "K3" in the subject. When they are found, those emails are put into a separate folder. Not owning a K3, that makes it easier for me to quickly scan through topics that probably aren't of interest to me. Some folks don't bother to put K3 in the subject, although the topic refers to some aspect of that radio. That's OK. I'm not complaining about that. However, when people start talking about radio mods, it seems imperative to me that they mention somewhere, preferably in the subject line, which radio they are referring to. In this case, there are CW mods for both the K2 and K3 (and probably K1 and KX1 as well). This was not meant to be a criticism. It's just a suggestion to possibly prevent unnecessary confusion. 73's, John AA0VE _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
|
|
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1 I agree John. The list moderators have asked, on several occasions, for people to put the model of elecraft product in the subject line. It was suggested that doing this would allow people to use the filtering capabilities of their mail clients to sort through all the mail and stick it in the right spots. It was also one of the excuses put forward to keep Elecraft from having forums where it's pretty simple to stick your message in the right spot. Got a K3 question, stick it in the K3 forum, Couldn't care less about the K3, don't read the K3 forum. How hard it it to put K3, K2, K1, KX1 in the subject line? My six year old granddaughter can do it. John R. Lonigro wrote: | Hi everyone: | I have Thunderbird check for the magic characters "K3" in the subject. | When they are found, those emails are put into a separate folder. Not | owning a K3, that makes it easier for me to quickly scan through topics | that probably aren't of interest to me. Some folks don't bother to put | K3 in the subject, although the topic refers to some aspect of that | radio. That's OK. I'm not complaining about that. However, when | people start talking about radio mods, it seems imperative to me that | they mention somewhere, preferably in the subject line, which radio they | are referring to. In this case, there are CW mods for both the K2 and | K3 (and probably K1 and KX1 as well). | | This was not meant to be a criticism. It's just a suggestion to | possibly prevent unnecessary confusion. | | 73's, | John AA0VE - -- R. Kevin Stover, ACØH -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFH8ihG11jxjloa2wsRAqBYAKC9gZ8xoULyy4ChO8K4U8R7+TKgywCeKf96 hdoh0Ab5PmArSy8i6L+T9lA= =0+jA -----END PGP SIGNATURE----- _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
|
|
In reply to this post by AJSOENKE
CONTENTS DELETED
The author has deleted this message.
|
«
Return to Elecraft
|
1 view|%1 views
| Free forum by Nabble | Edit this page |