[Elecraft] [Elecraft_K3] A Different View--K3 Reduced-bandwidthRTTY Analysis

[Joe Subich, W4TV]

> What I see, on both K3's here, is a brief 7% power spike upward when
> the FSK input is shorted, and a brief 7% power spike downward when
> the FSK input is opened.

Expect to see more change on keying edges with shaped/filtered/band
limited FSK.  Even shaped AFSK from 2Tone/cocoamodem/fldigi show
significant AM effects when switching from tone to tone.  Running the
band limited AFSK through hard limiting (driving an amplifier into
compression) will widen the signal out (although not as much as driving
a mic preamp into clipping).

73,

    ... Joe, W4TV


On 3/25/2013 5:34 PM, Dave Hachadorian wrote:
>> I notice that in the narrower signal spectrun the two tone peaks have
>> the same amplitude.
>
>> Many of us have wondered why our watt meters diddled like the RTTY tones.
>
>> Hopefully that is fixed too.
>
> That is not fixed.  I have two K3's, and have been running reduced
> bandwidth firmware for a couple of months now.  An LED wattmeter still
> shows significant flickering as RTTY is being sent, and screen current
> on a tetrode amp shows a lot of variation on its analog meter.
>
> What I see, on both K3's here, is a brief 7% power spike upward when the
> FSK input is shorted,  and a brief 7% power spike downward when the FSK
> input is opened.  Steady-state mark and space rf amplitudes are equal.
> The transients occur only at the transitions.  This experiment was
> repeated with DSP v 2.81 and is unchanged from earlier versions.  I
> guess, if the signal is clean, it's nothing to worry about, but it sure
> looks weird to see all that flickering going on.  I remember on my old
> TS-850, I could check amplifier tuning while rtty was being sent, but
> with the K3, I don't feel comfortable doing that.
>
>
> Dave Hachadorian, K6LL
> Yuma, Arizona
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