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, [EMAIL PROTECTED] 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" <[EMAIL PROTECTED]> To: "Elecraft Reflector" <[email protected]> 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: [email protected] > 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: [email protected] 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: [email protected] 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
