[Elecraft] K3 TX delay

Thu Feb 17 11:47:01 EST 2011

I respectively submit that the K3 does NOT have a QSK problem.

It sounds more like a discussion on how-many-angels-on-the-head-of-a-pin
with the QSK switch time substituted for angels.  It did have limitations
for very QRQ, but there is an option for that now. I like the hearing with
the QRQ mode QSK.  And OF COURSE I would like that in effect at all times.
 But that is the difference between breakfast and gourmet breakfast.  Some
are talking as if there is no breakfast at all.

In going below 8 ms state change time, one is working against many
state-change processes in the K3 and the need for offsets to settle when
working split and other similar issues.  The QRQ mode throws some of those
overboard in order to get really really fast QSK. (The QRQ QSK mode *IS*
really really fast.)  Split and XIT are issues in this mode because there is
only one transmit string, extensively state-switched and reused for main RX.
This cute switching on the main board saves a TON of circuitry and board
space and COST for the transceiver.  (You LIKED not having to spend ten
grand for your K3, didn't you....)

I have NEVER had an issue hearing in-between for either up-freq pileups or
on-freq listening for the station.  The REAL pathetic timing issue is *MY*
brain's inability to stop mid-baud when I hear DX come back.  The finish of
the letter (or two) seems to be on its own un-interruptible channel in my
cerebral cortex.  I'd be tickled pink if *I* could respond in 8 ms.  But
this response time is typical.  Even the grandkids are not that fast, though
they are plenty faster than me.  The weak element in turn-around time will
always be the HUMAN, by far.  No contest.  Nowhere near close.  8 ms is an
audio frequency (125 Hz). No human will be flipping decisions in the space
between two cycles of a 125 Hz sound wave.

In one very interesting (turned out to be human factors) set down about a
K3, where the complaint was not hearing between bauds, the situation was
remedied by changing the front end setting of "PRE" to "ATT" (yes on 160m,
too), backing off the RF gain until the band noise was a tad less than
moderate, and setting the AGC to slow.  All of a sudden the QSK "sprang to
life".  The operator was told to advance the AUDIO gain if a signal was in
the noise.  It appears that QSK does not "sound right" when using fast AGC
(my own impression as well), though looking at audio spectrum recodings of
what I was hearing proved that the IMPRESSION was ALL IN MY HEAD.  Was a
little deflating, but educational.

A penchant to blame the K3 at first perception leads to an inability to
drive it at the max.

Beyond all of that, most of the QSK restriction issues I have worked on
ultimately had to do with the transfer time **in the amplifier**, IMHO the
killer limiting factor in too-slow-QSK.  This has been true with high end
Acoms, SPE Experts, older Alphas, and certainly any Ameritron not equipped
with their pin diode option (my AL1200 is extensively modified to get an
honest 5-6 ms switch time).  In the case of two companies it took extended
arguments with their tech support to convince them there was an issue AT
ALL, and in both cases wound up in their having to invent a mod AFTER their
release, and sending the amp back to the factory to install it.  (Wonder who
was testing things before release.)

Reducing transfer time to 4 ms had better be done with diode switches in the
amp because mechanical TR state change in amps is rarely finished within 4
ms...think consistent TWO milliseconds closure for the relay to support 4 ms
timing, relay closure intervals GRADUALLY LENGTHEN with time and use. EVERY
brand amp has this restriction with a mechanical transfer, whether they
admit it or not. Doesn't matter what they advertise. Will be watching the
KPA500, but it's pin diode I hear.  I still wonder what happens to the
KPA500 pin diodes when you open with a dit into an unterminated coax and a
20:1 SWR.  Wayne and Co are working their magic into a problem that has
taken most amps down.  That problem IS Daniel into the lion's den,
regardless of who is playing the role of Daniel, even Wayne and Eric.  They
have to actually beat the lions and so far there are many wounded out in
amplifier land.

I have had to replace fast vacuum relays twice in amps loaned out because
operators set their delay to minimum...less than 8 ms...thank you Wayne for
cutting that off at 8 ms, thank you, thank you.  Transceivers were
transmitting RF before the relay contacts had settled and quit moving.  This
is a formula for key clicks, relay contact burning, contact welding, and
burned bandswitches and carbon tracks everywhere.  I have personally
repaired amps where nearly everything on the antenna side of the plate
blocking capacitor was ruined.  The Orions will actually allow the delay set
at zero.  The lame excuses from the relay-burner loanees went like "Well, we
were using the [insert brand] on the Alpha 89 just fine" (pin diodes). That
didn't cut it for me and all I got was "better sounding QSK" when I asked
them why they did it.  And no, they didn't pay for the work.

I find that I am able to hear just fine between dits at ordinary speeds on
the K3, and I can be broken into at up to 35 wpm reliably WITHOUT needing
the QRQ mode.  The very very fast QSK mode in the K3 allows for precision
code and RX/TX transfer at up to 75 wpm.  In this mode all the various
features that kill the milliseconds in TX/RX state change are disabled so
that some can have their 75 wpm QSK.

73, Guy.

On Wed, Feb 16, 2011 at 2:04 PM, Bill VanAlstyne W5WVO
<w5wvo at cybermesa.net>wrote:

> ... Which (QRQ mode) unfortunately isn't available, in practical terms, in
> the absence of the KRX3 second receiver, since working split or XIT is
> impossible. What a wonderful experience using this mode is, though! If only
> I could use it for chasing DX running offset pile-ups. Really justifies
> having the KRX3. It's on my must-have list, but a few other things have to
> come first. :-(
>
> I've also advocated to Elecraft in the past to make available RF delay
> settings below 8 ms for those of us who have fast QSK amplifier switching
> using vacuum relays or switching diodes. (My homebrew 6m amplifier T-R
> speed
> is well under 4 ms, for example. The new Elecraft amp, I assume, will be
> even faster.)
>
> I'd also like to see the CW WGHT parameter (optionally) configure itself to
> conform to the amount of RF delay selected in concert with the speed
> selected for the internal keyer. Right now, the default CW WGHT value of
> 1.10 is optimized for a QSK RF delay of 8 ms (default) and a keyer speed of
> 20 WPM. (Do the math.) However, an ideal CW WGHT value could easily be
> computed automatically from these two parameters, giving you the
> best-shaped
> CW elements at different sending speeds, on the fly. (Of course, such a
> feature would only work when using the internal keyer, not an external
> one -- unless autodetection of CW sending speed was also incorporated.)
>
> Bill W5WVO
>
>
>
> -----Original Message-----
> From: Vic K2VCO
> Sent: Wednesday, February 16, 2011 16:00
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K3 TX delay
>
> No, you can't change this, but the best QSK performance comes from
> activating QRQ CW mode.
>
> On 2/16/2011 2:17 AM, Adrian wrote:
> > Is it possible to reduce the K3 TX delay down to 4ms from the current
> > 8ms minimum for qsk use?
> >
> > Adrian ... vk4tux
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:Elecraft at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
>
> --
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco/
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>