[Elecraft] K3 and RTTY

[Fred Jensen]

Items, questions, and requests do tend to morph on this list.  While I 
don't disagree with your reply, please keep in mind ... the original 
request was from someone who wanted to try RTTY for the first time, and 
that's where my reply was directed.  I wanted to make it as easy as 
possible for him, and unquestionably, two steero cables and AFSK is 
that.  With a K3, that will work, and won't clobber folks near him

He may choose other methods or indeed modes, all he seemed to want was 
initial advice.  You're not wrong, you rarely if ever are, but the 
information may be misplaced in this case.  He just wanted to get started.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
- www.cqp.org

On 1/30/2015 7:19 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
>
>
> On 2015-01-30 9:34 PM, Tony Estep wrote:
>> On Fri, Jan 30, 2015 at 5:29 PM, Fred Jensen <k6dgw at foothill.net> wrote:
>>
>>> Ummmm ... I've never understood the infatuation with FSK over AFSK....
>>>
>>> For those who believe that FSK has some advantage over AFSK for purity
>> signal or some other reason, K0SM has posted a detailed web page showing
>> the spectra of signals generated by both, using various transmitter
>> adjustments. Check it out at:
>>
>> http://www.frontiernet.net/~aflowers/k3rtty/k3rtty.html
>>
>> 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.
>>
>> 73, Tony KT0NY
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