[Elecraft] K1 carrier rise/fall times unequal?

[Don Wilhelm]

David,
I don't have a K1 that I can measure, but I would not be overly concerned
about the explicit fall time.  The keying waveshape is not really a true
square wave, so to me the most important factor is the presence of any
overshoot tendencies which are an indication of keyclicks (I assume you see
none on the keying waveshape).  I do know that the keying in the Elecraft
rigs has been described as "chrisp" and "nice to listen to", so perhaps the
short damped fall time is the mechanism that produces this chrispness.

As far as bandwidth of the signal goes - the waveshape alone does not tell
the whole story because the keying speed is also a primary factor - a 10 wpm
CW signal is more narrow than a 30 wpm CW signal and so on.  I also trust
that when you plan to operate to within the last kHz of your allocated band
you would have more accurate measurement capability than the readout on your
transceiver dial (I personally would not trust ANY transceiver to provide
that accuracy without frequent reference to a known standard, and I do not
intend any disparity toward an Elecraft product or any other product by
making that statement).

73,
Don W3FPR

----- Original Message -----
>
> While researching the basic accuracy of my new K1's accuracy display, I
> discovered with an oscilloscope that my unit transmits with about a 5 ms
> carrier rise time, but with a carrier fall time of only about 1 ms.
Having
> learned that the bandwidth of the transmitted signal is a function of the
> keyed carrier's rise and fall times, I'm wondering now whether a 1 ms fall
> time is normal.  According to Figure 12.21 of the ARRL Handbook (2003) in
> the chapter on modulation sources, a 5 ms rise time signal will have a 150
> Hz bandwith, but a 1 ms fall time corresponds to a rather large 700 Hz
> bandwith.  This signal bandwidth, plus the basic accuracy of the K1's
> displayed frequency, affect just how close to a band's edges I would want
to
> set my frequency when transmitting.
>
>