[K4] First Impressions of K4 SN122 (LONG!)

[Rick Miller - N1RM]

I put SN122 through its initial paces today.  Here are some of observations:
Appearance and general behavior:
1. This is a very good looking radio.  The front panel design looks great.
2. The rear panel has more room than the K3.
3. The BNC connectors protrude farther out the back panel than the K3, and
look a little strange to me. (But who really cares what the back panel looks
like!)
4. The touch screen is extremely easy to read in all lighting conditions
that I've used so far (it's gorgeous!).
5. The touch response is very good, though every once in a while it seems to
have to "think" a little before responding.

Build quality:

1. The cabinet fit and finish are as good as I've seen. It's very solid and
the finish is great.

2. The interior is very interesting. Most parts appear to be very cleanly
integrated. The CPU has a bit of a "tacked on" appearance.  I applaud
Elecraft for not trying to design their own high performance processor
board, but the interface cabling looks a little ad hoc. It all works, but I
have to wonder how it would survive getting knocked around enroute to a
Dxpediton.

3. The front headphone jack was completely dead on my radio, but the rear
headphone jack was fine. It was pretty easy to figure out how to release the
front panel (thanks to Wayne's excellent video on the 3D model of the K4).
The front headphone jack attaches to its circuit board with a socket that
plugs onto a 4-pin header. That connector was completely off the header.
When I connected it, I noticed that the insertion force was almost nil, so
it's likely that it came off during shipment.  I slightly bent a couple of
the header pins to provide a little more friction. When I got it back
together it worked fine.  I believe that it would be good to consider adding
more physical restraint to that connection.

4. The pushbutton switches on the front panel are much more solid, with
better tactile feedback than the K3. I like them much better.

Operating impressions:

1. Rx audio seems to be less fatiguing than the K3.

2. Tx audio reports were very good (from trusted critical sources).

3. Tx audio compression seems to be very weak compared to the K3.  Even at
30 (max setting), it seemed to do less than a setting of 10 on the K3. It
might need some DSP attention.

4. Most of the UI is absolutely great.  Things like setting EQ levels for Tx
and Rx using a touch screen were a real dream-come-true. There are multiple
ways to do many things, and there is a little bit of irregularity in the
ways to do things. However, overall I think it is very easy to use given the
complexity and huge variety of controls that are needed.

5. The spectrum display system is a work of art. I always found it necessary
to have an external monitor on the P3 to make it really effective. In most
cases, I feel that the spectrum display on the K4's built-in screen could
stand alone. However, I'm hanging on to my external monitor because the
ability to configure it independently of the built-in screen likely will
open up many valuable use-cases for display management.

6. Data and CW decoders can run simultaneously on the A and B VFO
frequencies. So this radio can actually copy two different QSOs at the same
time.  That's very cool.  Also the CW decoder seems to work better than the
K3's, though that's hard to quantify. One caveat - I believe using both
decoders is effectively a "multi-channel decoder" as defined by some contest
rules. You may want to check before enabling it during a contest to ensure
it doesn't put you into the Assisted category if you don't want to be there.

Station installation:

1. My goal was to disconnect my K3s/P3 pair, and then "drop in" the K4,
making note of the changes that needed to be made.  It turned out to be very
easy to get it going in my station.  Here's a quick summary of what I did:
  a. For CAT control, I moved the DE-9 from the P3 to the DE-9 on the K4,
removing the daisy chain cable between the radio and the P3.
  b. The K-Pod changed from its original custom cable to a standard USB
cable going to the back panel.
  c. The external monitor changed from a VGA connector on the P3 to an HDMI
connector on the K4 (fortunately my monitor has an HDMI port).
  d. I added a (shielded) Ethernet connection.
  e. I removed the IF plumbing for the P3.
Everything else was identical between the K3 and K4. That includes keying in
and out, accessory connector going to KPA/KAT500, custom TX inhibit input,
and Mortty FSK. Special shoutout to N6TV for the awesome Y-box!  Since I
used the RS-232 serial connection for control, I didn't have to change
ANYTHING in N1MM to take control of the K4.  It just worked! All I had to do
was select the different sound card instantiation that appeared in windows
to get data modes working. Actually, I also needed to select the correct
inputs on the K4 for the different modes and set levels. But the transition
from a fully integrated K3s/P3 to a fully integrated K4 was less than an
hour, including full N1MM integration. There are so many different ways to
integrate both the K3 and K4 that your mileage will almost certainly vary.

2. The K4 takes less room horizontally than the K3/P3 combo, but it is
deeper (see attached photos).  That actually helped me because the front
panel ended up a little closer to me than the K3's did.  I have a pretty
deep desk, but if you have tight quarters in front of your K3, you may have
to rearrange some things.

One weird thing:
1. I noticed very shortly after I turned the radio on for the first time (AF
gain at zero, no antenna connected) that I thought I had a ringing in my
ears.  When I turned off the radio it went away.  It wasn't loud, it just
felt like a very slight case of tinnitus. It was sort of like one of those
high pitched tones that you try to guess if it's there during a hearing
test. I noticed that it seemed to come and go as the display came up and
went away. (I resisted the urge to hold my finger up and down as it came and
went :) Then I noticed that it got fainter if I turned the display
brightness down.  Just to be sure I wasn't imagining it, I hooked a
microphone up to my PC and Audacity, held it in front of the display, and
then powered up the radio.  I could see nothing in the time domain, but when
I ran a spectrum on it, there was a very distinct spike at 10 kHz. The spike
disappeared with the radio off. The "ham demographic" probably includes very
few who could hear it, but I'm one of them.  Just to put it in proper
perspective, I'm that guy who during sound checks in church says "where is
that squeal coming from?" and everyone else looks at me like I'm nuts.  It's
just barely on the edge of being annoying, but there is hopefully something
that can be done to mitigate it for those of us that can still hear weak 10
kHz audio. My guess is that it is a DC-DC boost converter somewhere in the
display with a ringing inductor.

Bottom line:
While very reminiscent of the K3, this is NOT a K3. It sounds better on Tx
and Rx and its UI is a whole new animal for Elecraft (in a good way!). It
has far more connectivity and control options than the K3, which means you
will have to invest some time to learn how the K4 thinks and acts.  I waited
exactly 2 years (to the day!) for this radio, and I can say that it was
certainly worth it for me.  Congratulations to Wayne and the whole Elecraft
team for getting this radio out under some really tough conditions.

73, be safe, have fun!

Rick Miller
N1RM

<http://elecraft.365791.n2.nabble.com/file/t246436/N1RM-K3.jpg>
<http://elecraft.365791.n2.nabble.com/file/t246436/N1RM-K4.jpg>



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[wayne burdick]

[Re-posting my reply to the original post on groups.io]


> On May 19, 2021, at 12:03 AM, N1RM - Rick Miller <[hidden email]> wrote:
>
> I put SN122 through its initial paces today.  Here are some of observations:

Thanks, Rick. My comments below.


> 3. The BNC connectors protrude farther out the back panel than the K3, and look a little strange to me. (But who really cares what the back panel looks like!)

Unlike the K3, the five BNC connectors on K4 have bushings that are used to physically and electrically secure the connectors to the rear panel. This is part of the overall noise-reduction strategy. It also provides very rigid mounting for the RF board.


> 2. The interior is very interesting. Most parts appear to be very cleanly integrated. The CPU has a bit of a "tacked on" appearance.  I applaud Elecraft for not trying to design their own high performance processor board, but the interface cabling looks a little ad hoc. It all works, but I have to wonder how it would survive getting knocked around enroute to a Dxpediton.

Our goal here was to be able to adapt to future single-board-computer technology rather than be constrained to what's available today. Swapping boards would be a matter of adjusting mounting screw locations on the replaceable adapter bracket and at worst, replacing a couple of cables.

>
> 3. The front headphone jack was completely dead on my radio, but the rear headphone jack was fine. It was pretty easy to figure out how to release the front panel (thanks to Wayne's excellent video on the 3D model of the K4). The front headphone jack attaches to its circuit board with a socket that plugs onto a 4-pin header. That connector was completely off the header....

We're going to improve the mating connectors. Thanks for finding and reporting this.


>
> 4. The pushbutton switches on the front panel are much more solid, with better tactile feedback than the K3. I like them much better.

This is due to our use of real tact switches beneath the rubber in the K4. The K3 (and our other products with rubber switch matrices) uses carbon-dot contacts that rely on hysteresis in the rubber itself.


> 3. Tx audio compression seems to be very weak compared to the K3.  Even at 30 (max setting), it seemed to do less than a setting of 10 on the K3. It might need some DSP attention.

Agreed. This is on our list.


>
> 4. Most of the UI is absolutely great...
>
> 5. The spectrum display system is a work of art...

> 6. Data and CW decoders can run simultaneously on the A and B VFO frequencies...

Thanks for these observations :)

>
> One weird thing:
> 1. I noticed very shortly after I turned the radio on for the first time (AF gain at zero, no antenna connected) that I thought I had a ringing in my ears.  When I turned off the radio it went away.  It wasn't loud, it just felt like a very slight case of tinnitus. It was sort of like one of those high pitched tones that you try to guess if it's there during a hearing test. I noticed that it seemed to come and go as the display came up and went away. (I resisted the urge to hold my finger up and down as it came and went :) Then I noticed that it got fainter if I turned the display brightness down.  Just to be sure I wasn't imagining it, I hooked a microphone up to my PC and Audacity, held it in front of the display, and then powered up the radio.  I could see nothing in the time domain, but when I ran a spectrum on it, there was a very distinct spike at 10 kHz. The spike disappeared with the radio off. The "ham demographic" probably includes very few who could hear it, but
 I'm one of them.  Just to put it in proper perspective, I'm that guy who during sound checks in church says "where is that squeal coming from?" and everyone else looks at me like I'm nuts.  It's just barely on the edge of being annoying, but there is hopefully something that can be done to mitigate it for those of us that can still hear weak 10 kHz audio. My guess is that it is a DC-DC boost converter somewhere in the display with a ringing inductor.

We'll definitely investigate whether it's a DC-DC converter on the front panel board or within the LCD itself. If there's a way to suppress the 10 kHz a bit, we'll find it.


>
> Bottom line:
> While very reminiscent of the K3, this is NOT a K3. It sounds better on Tx and Rx and its UI is a whole new animal for Elecraft (in a good way!). It has far more connectivity and control options than the K3, which means you will have to invest some time to learn how the K4 thinks and acts.  I waited exactly 2 years (to the day!) for this radio, and I can say that it was certainly worth it for me.  Congratulations to Wayne and the whole Elecraft team for getting this radio out under some really tough conditions.

Appreciate the feedback!

73,
Wayne
N6KR





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