Thanks to Doug for the clarification of the hardware aspect of the DSP board
upgrade. This has allowed me to do some research with my own K3's.
First of all, the term artifact seems to be used these days as a catch all. I
have heard rumbles, funny pops and ticks that were seemingly in the
foreground of my IC756 and have taken a very negative view of this - DSP
artifact generally means to me, odd beyond the point of accepting under normal
conditions. I have analog ears, guys who got their first HF with DSP are
probably okay with that type of thing.
I went searching for an artifact in the K3 transceiver having not encountered
one before. I remembered that I had the upgraded DSP board for low range audio,
but unfortunately a very early one that had no lettered marking on it at all,
and no daughterboard. So, I was 99% confident that my K3 was ready to exhibit
some artifactual behavior, and I would decide if it was objectionable enough to
want the $24 upgrade LPF.
I searched NABBLE and found one of the first reports of this in early Spring to
be sounding like Jingle bells. Hmmm, never heard that. But I knew to look for
jingle bells at approximately 4 khz and 78db down (weak). I put the K3 on 7
Mhz LSB at night and found a strong SWL signal. I went into the RX Eq and put
all sliders at negative 16 EXCEPT number 8 (rightmost) which I put at +16.
What did I hear? Sleigh Bells!. That is quite different from Jingle Bells and
although disappointed, it made more sense. ;-) It was plain as day - I am
assuming I have found the artifact.
I pressed the CLR button to set the Rx EQ to FLAT, and I seriously could no
longer hear this artifact. I cant think of any scenario, ever when that
rightmost EQ would be above ZERO. But for those that want to hear up there in
dog whistle range, or those that can hear it naturally better than I can using
a practical EQ setting, Elecraft has gone the extra mile. I hear as well as
anyone as a reference, but as Doug suggests, the headphones may be a possible
factor. I favor the speaker, 2 of them in fact.
I applaude Elecraft for going to all the trouble and expense of engineering a
daughterboard for this, and maintain once again that to my ears, K3 is the only
IF DSP transceiver that sounds analog. The AGC is Q5, no artifacts in the
foreground, and minimal DSP filter noise.
Just as a point of reference and no Icom bashing here, but Icom produced a
document when the 756Pro was introduced, explained rumble and suggested that
if you were the type to enjoy record albums, etc. - you may not like the sound
of their transceiver. I have no idea what Elecraft did differently.
I won't be adding the LPF mod - at $24 bucks. It's cost is trivial and I
-enjoy- applying mods to my sets, but if there was ever a case of not broke
don't fix, this is it for these ears.
73,
Don
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