[Elecraft] DATA-A tx freq offset with digital modes

Thu Sep 22 18:26:22 EDT 2016

Eric,

As an old duffer who has done lots of scientific writing over the last 
60 years, I have never found that I could ACCURATELY proofread from a 
computer screen.  For some reason, my eye skips over some really howlers 
which I do catch in the printed copy.  And along with this is the 
growing incidence of spellchecker errors, in which the wrong real word 
is substituted for a misspelled word with another meaning.  (My favorite 
error was the substitution of "wooden" for "woolen" in  a sentence which 
was intended to read "[she] was the type of girl who looks like she 
wears woolen underwear."  I hope the younger generations are better than 
I am, but looking as the printed results does not encourage this belief.

George, W3HBM
PS - I hope this short message is error-free, but don't count on it - I 
didn't print it out.

> A very enlightening post, Guy.
>
> Almost every new technology ever invented experiences the same thing. New users tend to work hard to make the new technology work just like the old technology did. Instead of developing new procedures to fit very different technology, they make the new technology fit the old procedures. I worked in the printing and publishing industry for many years.
>
> We were still using some hot metal Linotypes that weren't even made anymore, and when we bought electronic typesetters, managers and workers tried to make them compatible with hot type instead of junking hot type and developing new procedures. It was a long battle. Computer use was the same. People would type on the new word processors, then immediately print a copy to edit from, then go back to the WP enter the edits and immediately print a "clean" copy. One wag early on said the paperless office was about as likely as the paperless bathroom.
>
> Thanks for the very lucid description of how the K3 works.
>
> Eric KE6US
>
> On 9/22/2016 1:21 PM, Guy Olinger K2AV wrote:
>
> [In the following text, "both the K3 and the K3S" is represented by "K3/S".
> Text applicable to only one or the other will be "K3" or "K3S"]
>
> Hi Graham.
>
> With a warm smile, a soft voice, and friendly demeanor. I have had to go
> through this post-analog era "de-analoging" my own radio perceptions, and
> have had a fairly painful time of it :>)
>
> The big lesson from my de-analoging was just how much my traditional analog
> thinking, ground in by 50 years of analog hamming experience on analog
> equipment, was keeping me from moving on. I needed to understand, cope with
> and take advantage of very superior digital methods in a new digital era. I
> was really pretty clunky. That said, not reporting any genius-level
> learning rate on my part to claim superiority...
>
> There is no suppressed carrier in software derived radio (SDR). In the
>   K3/S the single sideband envelope is generated directly from firmware. It
> begins with data from analog to digital converter chips (ADC) on line in or
> mic leads. Firmware converts this to SSB representative data, sent to a
> digital to analog chip (DAC) directly outputting SSB at the 15 kHz TX IF.
> There is no carrier to null or filter out. There is no opposite sideband to
> phase out or filter out. There are DAC and frequency conversion artifacts
> which need to be removed by one means or another (as in going through a 2.7
> kHz wide 8 MHz crystal filter also used for receive).
>
> CW is not a keyed carrier any more. It is directly generated by the DAC
> chip to the 15 kHz TX IF from digital data representing an ideal waveform.
> The normal keying "sidebands" of the CW signal are also from that data. The
> frequency conversion, and linear amplifier stages following, will add some
> additional sidebands based on their degree of linearity, hopefully very
> well down.
>
> For frequency display, in CW mode the K3/S will display the single
> frequency of the central signal.
>
> For SSB and any mode generated through DATA A, the K3/S will display the
> traditional amateur radio SSB frequency, which is what you would get if you
> could somehow create SSB output from a DC voltage applied to the K3/S
> transmitter line in or mic inputs. Note that some other radio services use
> center of bandwidth as the frequency for SSB operation.
>
> Use of audio input for keying should be avoided where possible. Note that
> you can generate CW, FSK, and PSK without use of audio input, producing
> ideal keying and bandwidth. Signals generated this way are without any
> audio input artifacts like 60, 120, 180 Hz hum, audio harmonics from low
> level distortion, audio noise or hiss, or miscellaneous unwanted audio from
> grounding issues, or feedback from mild RF in the shack, or miscellaneous
> audio from other apps on the PC bleeding through PC "soundboards".
>
> The state of digital direct signal generation for CW is so clean that it is
> simply poor amateur practice to generate CW from audio tones. There are so
> many ways to screw up CW in the audio. The reputation of very clean CW from
> K3/S depends on the direct data generation of CW in the K3/S
>
> The key jack input on the back of the K3/S is itself converted to data on
> one lead of an ADC chip, and sent to the CPU as data, only one data
> "channel" on a single multiplexed data line, informing the CPU that the key
> is *reported* high or low. That key jack voltage is not used directly for
> anything except to be sampled, and advise the CPU whether the jack is keyed
> or not. The CPU directs other stuff based upon the *report* of keyed or
> not. It can do exactly the same thing from a string of characters converted
> in firmware to the *effect* of *reports* of keyed or not. Ditto FSK D and
> PSK D.
>
> In a contest, I would not want to be the next station up or down frequency
> from you doing audio generation of CW. I urge you to permanently
> discontinue that practice.
>
> I would also urge that you use FSK D and PSK D where possible to transmit
> instead of audio tones. These are all successfully employed by some remote
> users, though I can't speak to the methods or their complexity.
>
> FSK D and PSK D will occupy minimum bandwidth by virtue of ideal waveforms
> and be independent of all the audio train issues of gain, noise,
> level-based distortion and AC power artifacts between user PC generation,
> audio train, and the K3/S.
>
> Use of the K3/S USB "soundcard" in some setups does remove some audio
> transmission issues, but you are exporting the "quality control" of
> waveforms to the third-party program running on the PC. Third-party
> programmers are not going to take responsibility for K3/S output waveshape.
>
> Sorry to rag on, but not excessively sorry.  :>)
>
> 73 and good luck with all the remote stuff.
>
> Guy K2AV
>
> On Thu, Sep 22, 2016 at 1:37 AM, Graham Alston <graham at alston.com.au><mailto:graham at alston.com.au> wrote:
>
>
>
> Hi,
>
> I’m very new to Elecraft and K3S so hope this is not too obvious….
>
> I have a K3S connected to my PC with audio tones coming in via MIC IN (in
> reality the K3S is the remote end of a K3-Twin remote setup).
>
> When I use DATA-A sub mode for CW, the transmission is 600Hz higher than
> the VFO frequency. I assume this is because DATA-A transmits on the USB and
> the VFO shows the suppressed carrier frequency?
>
> I want my CW signal to match the VFO, how can I do that?
>
> 73, Graham VK3GA
>
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