[Elecraft] K3 and RTTY

[Wes (N7WS)]

Well, since the subject is "K3 and RTTY", isn't it fairly safe to assume that a 
K3 would be in this picture?  If so, then AFSK is, IMHO, the simplest method and 
you agree that it "is acceptable."

Wes  N7WS



On 1/30/2015 8:19 PM, Joe Subich, W4TV wrote:
>
>> This page has many virtues. It shows how to do a nice job of research
>> and how to document it for the reader; it offers useful info about
>> setting up your RTTY station; and it provides hard data, which is a
>> lot better than relying on conventional wisdom.
>
> Unfortunately, K0SM's paper has flaws in its premise that render the
> conclusions hardly persuasive.
>
> 1) the FSK measurements were made with the *original* K3 FSK generator
> not the most recent shaped FSK.  Even though the original K3 FSK was
> better than most, the current DSP implementation is much better and
> provides FSK indistinguishable from the filtered AFSK.
>
> 2) the AFSK measurements were made using Line In and did not include
> effects common to overdriving the microphone preamp as happens in
> many rigs.
>
> 3) in the K3, AFSK_A disables mic compression and RF clipping. That
> is not the case in other transceivers operated in SSB mode.  The mic
> compression and RF clipping is one source of AFSK distortion and
> harmonic generation.
>
> 4) the AFSK measurements were made with the K3's AFSK TX filter in
> line.  That filter removes substantially all the hum and distortion
> present in other transceivers when the ground (audio) return is open,
> the sound card DAC is driven into the distortion producing range
> (typical at output levels greater than 60%), and/or the mic preamp is
> being overdriven.  Andy's tests with all knobs full bore proved that
> the K3 is capable of cleaning up signals that would be a disaster with
> many other rigs.
>
> 5) The K3 does not use a "closed loop" ALC which generates overshoot
> and "pumping" distortion.  Again, these effects are common on other
> manufacturer's transceivers and are often responsible for a high
> preponderance of the "clicks" in both FSK and AFSK signals from those
> transceivers.
>
> I have off the air spectrum captures of W1AW with their top of the
> line Icom rigs and professional operators that show *all* of the
> issues of overdrive, loss of signal return and ALC effects even when
> driven by supposedly "clean" AFSK signals from fldigi.  Again, AFSK
> requires far more operator attention to "signal hygiene" than does FSK
> if the result is to be acceptable (that is, unless one is using a K3).
>
> 73,
>
>    ... Joe, W4TV
>