[Elecraft] New Elecraft K4 has great Rx Audio on CW pileups, no more mush

Tue Jun 23 12:20:53 EDT 2020

Paul,

The K4's DSP smoothly ramps audio up/down during muting. There's no "clamp." 

The artifacts in the recording are not coming from the K4; they're probably due to RFI getting into the external recording device's cables, as Bob mentioned in his posting.

Wayne

> On Jun 23, 2020, at 9:11 AM, Paul Hvidston <phvidston at gmail.com> wrote:
> 
> Just sounds like the audio muting during key-down. The K4 speaker
> probably rolls off below 300Hz while your recording has higher fidelity.
> External audio devices would have to roll off the low frequency to avoid
> it. I bet if the K4 used a VCA rather than a simple clamp you probably
> would not hear this on the line-out during keying. No idea if it is
> simple hardware or a DSP operation (easily fixed). Either way, the K4 is
> impressive.
> 
> 72 de Paul/N6MGN
> 
> On 6/23/2020 7:23 AM, Victor Rosenthal 4X6GP wrote:
>> I certainly hope the clicking I hear on the sidetone is an artifact of
>> the recording process, or something that will go away with the
>> production version of the K4!
>> 
>> 
>> 73,
>> Victor, 4X6GP
>> Rehovot, Israel
>> Formerly K2VCO
>> CWops no. 5
>> http://www.qsl.net/k2vco/
>> .
>> On 23/06/2020 12:41, Bob Wilson, N6TV wrote:
>>> Summary:  The K4D Receiver Audio and QSK performance seems
>>> outstanding --
>>> I'm sold.
>>> 
>>> I hesitated to order a K4 until I could hear how one sounded in "real
>>> world" pileup conditions, compared to my trusty 11-year old K3s (S/N
>>> 1494
>>> and 1495 with KSYN3A upgrades).
>>> 
>>> Well, here is a short recording I made while operating a K4D Field Test
>>> unit during the All Asian CW Contest this past weekend, so you can
>>> have a
>>> listen to the QSK performance and the audio tones when several
>>> stations are
>>> calling on about the same frequency all at once, which is the typical
>>> "pileup mush" situation that has been so difficult for most modern
>>> radios
>>> to handle (including the K3):
>>> 
>>> https://www.kkn.net/~n6tv/Pileup_Audio_on_K4D_Field_Test_N6TV.mp3
>>> 
>>> (Headphones recommended).
>>> 
>>> With 2 or 3 guys calling, it seemed *so* much easier to pick out
>>> callsigns
>>> with the K4D, compared to my K3, especially when they were very close in
>>> frequency, which was often.  The audio distortion and "beat note
>>> buzzing" I
>>> still occasionally hear on the K3 is not heard on the K4. *This alone is
>>> reason enough for me to order a second K4D* for SO2R contesting.
>>> 
>>> Note:  The "thumps" and clicks you hear in the recording while I'm
>>> transmitting with full QSK are mostly a side effect of the analog
>>> recording
>>> method  used (rear headphone jack, long cable, ungrounded radio, and
>>> microHAM MK2R+ sound card).  I think some RF is still getting into the
>>> MK2R+ despite lots of ferrites.  The "thumps" are not heard in the front
>>> panel headphone jack of the K4.  The stereo USB Sound in the K4D
>>> won't have
>>> these issues.
>>> 
>>> I also toggled PRE1 and NR (level 4) when a weak one would call, and it
>>> really seemed to help pull them out of the noise.  I put both
>>> receivers on
>>> the same frequency and used A/B to toggle both settings ON and OFF at
>>> the
>>> same time with a single tap (Main RX had PRE OFF and NR OFF, Sub RX had
>>> PRE1 ON and NR ON, and I would swap them).  I modified my Win-Test
>>> scripts
>>> <https://bit.ly/wtscripts> so I could swap A/B from the keyboard of my
>>> logging program.  I've also made scope control work from the Win-Test
>>> keyboard, as with my P3 scripts.  The radio responds to CAT commands
>>> instantly, as does the touch screen display.
>>> 
>>> Unlike the K3, I could keep the RF Gain at MAX and hear no real problem
>>> until the bands got really noisy, then backing it off helped a bit,
>>> as did
>>> the attenuator.  But I like the way the fast AGC worked.  Loud stations
>>> never hammered my ears, and there's a new "AGC attack time" setting
>>> that we
>>> don't have in the K3 that will require further experimentation.
>>> 
>>> As for QSK, I went back and forth between QSK ON and QSK OFF, Delay
>>> 0.00.
>>> There's a huge difference.  QSK OFF Delay 0.00 is much quieter, but I
>>> like
>>> to hear more between elements.
>>> 
>>> QSK performance was *way* better than the K3, especially at high
>>> speed (I
>>> went up to 39 WPM).   Amp. is a KPA1500.  No CW jitter was observed,
>>> so "CW
>>> QRQ" mode is no longer needed to send clean CW at high speed with either
>>> internal or external keying. I used 5 ms of keying compensation and got
>>> good reports from that, but I need to get out my scope and make some
>>> measurements.
>>> 
>>> I figured I would eventually want to order the K4 "HD" model, but I
>>> may not
>>> need it.  So far the receiver performance seems really good, even when
>>> getting close to loud signals.  But I don't have a way to make the
>>> careful
>>> receiver performance measurements that Rob Sherwood, NC0B, can make.
>>> 
>>> The band scope has much finer resolution than the P3 or an IC-7851,
>>> but I
>>> still need to experiment with an external HDMI monitor, which will
>>> provide
>>> even more pixels for the band scope.
>>> 
>>> Physically, a  K4D is smaller than the K3/P3 combo. side by side, and
>>> it's
>>> only about 3/4" taller and maybe an inch deeper.
>>> 
>>> The K4 buttons have a very nice tactile feel, much improved over the K3.
>>> Every knob except AF Gain seems to be an optical encoder rather than
>>> a pot,
>>> which means there is potential to control just about everything from
>>> your
>>> logging program keyboard, without having to touch the radio.
>>> 
>>> The "tap to tune" feature of the waterfall display seems to work well
>>> for
>>> making big frequency movements.  I need to try it with a USB mouse. 
>>> Better
>>> than that, there's a new method to automatically adjust the band noise
>>> level on the scope so you don't have to constantly fiddle with a "REF
>>> LVL"
>>> setting as we do on the P3.
>>> 
>>> There's more to write, but this post is long enough already.
>>> 
>>> In sum, I know we've all been waiting a long time for the K4 to be
>>> delivered.  I think it will be well worth the wait, and that your
>>> patience
>>> will be rewarded.  Meanwhile, me and my fellow volunteer Field
>>> Testers will
>>> be very busy trying to find all the bugs so that you won't have to. :-)
>>> But as delivered to us, it seems very stable, and very usable.  Most
>>> of the
>>> major features are working quite well at this point.
>>> 
>>> 73,
>>> Bob, N6TV
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> 
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