Posted by
Bob Wilson, N6TV on
Jun 12, 2020; 2:37pm
URL: http://elecraft.85.s1.nabble.com/CW-rise-time-setting-tp7661876p7662093.html
The plot in the *QST* review of the K3S shows the delay between "key
closure" (the KEY jack of K3S) and RF out. My plot shows the delay between
"amp relay closure" (the KEY OUT jack of K3S) and RF, which is more
critical.
Most folks assume there will be no delay between KEY closure and KEY OUT
closure, but there is an extra delay (of about 5 ms, minimum) in the K3S.
The same applies to PTT IN closure and KEY OUT closure; that is, there is
an unexplained fixed 5 ms delay in the K3S, probably due to slow firmware
logic testing for TX Inhibit or an intentional enforcement of some minimum
delay in RF output.
Most radios close KEY OUT immediately upon key closure of either the KEY
jack or the PTT IN jack. The K3 does not; it "hesitates" before closing
KEY OUT.
I'm also hoping the K4 will eliminate this unusual behavior.
73,
Bob, N6TV
On Fri, Jun 12, 2020 at 3:23 AM E.H. Russell <
[hidden email]> wrote:
> Bob,
>
>
>
> Thanks for the scope shot and info. I compared the waveform to the QST K3S
> review, which seems to show a little over 10ms before RF appears. Is this
> because they used different settings?
>
>
>
> Will be interesting to see how the new radio CW looks in time and
> frequency domains. Also how the turnaround latency is managed.
>
>
>
> Tks,
>
> 73 Ed w2rf
>
>
>
>
>
>
>
> *From:* Bob Wilson, N6TV <
[hidden email]>
> *Sent:* Thursday, June 11, 2020 2:05 PM
> *To:* Elecraft Reflector <
[hidden email]>
> *Cc:* E.H. Russell <
[hidden email]>
> *Subject:* Re: [Elecraft] CW rise time setting
>
>
>
> On Mon, Jun 8, 2020 at 12:31 PM E.H. Russell <
[hidden email]> wrote:
>
> I suppose shaping of the curve corners removes harmonics introduced by the
> abrupt transitions, allowing an accelerated ramp inbetween. But does this
> really reduce the total rise time to 2.5ms? It seems that the softening
> process must take some time. Wish I had a K3 here to scope against other
> radios. Anything published out there?
>
>
>
> Ed,
>
>
>
> Per your request, I am publishing this scope screen capture which plots
> the CW rise time in my K3 with the KSYN3A synthesizer upgrade. It's about
> 4 ms from 0 RF to full RF (2 ms per horizontal division):
>
>
>
>
https://www.kkn.net/~n6tv/N6TV_K3_Ser_1494_FW_05.64_TX_DLY_8_CW_QRQ_OFF.png>
>
>
> The vertical markers are there to illustrate that *CONFIG:TX DLY nor 008*
> provides only about *6 ms* of RF delay after "KEY OUT" goes to ground,
> not 8 ms, and there is jitter in that delay as well (not shown). If CW QRQ
> mode is enabled, the delay drops to about 4.6 ms and the TX DLY setting is
> completely ignored.
>
>
>
> This was discussed here two years ago. See this post for suggestions on
> how to avoid hot-switching a non-Elecraft amplifier driven by a K3 or K3S:
>
>
>
>
>
http://elecraft.365791.n2.nabble.com/Default-K3-transmit-delay-may-be-too-short-for-slow-QRO-amplifiers-td7641779.html>
>
>
>
> 73,
>
> Bob, N6TV
>
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