[Elecraft] K2 purchase considered

barry halterman kthreebo at gmail.com
Sat Nov 21 17:15:50 EST 2020 

Thank you Dave for the explanation on the reflector. I know there are a lot
of K2 fans on here and I don't want to discourage anyone from a K2, nor do
I want to say the K2 is not a fantastic radio. It is, except when tuning
around strong signals.
Barry

On Sat, Nov 21, 2020, 1:51 PM Dave Van Wallaghen <dave at w8fgu.com> wrote:

> Fellow listers,
>
> I'd like to add some clarity to the audio chirp problem mentioned by
> Barry. As some of you may or may not know, I took over for Don Wilhelm,
> W3FPR when he retired in February of 2019. I am a third party service
> provider through my company W8FGU Services, LLC as well as an employee
> of Elecraft providing support and servicing of their Classic Line of
> products.
>
> Barry contacted me a few months ago to report the chirping (popping)
> problem and sent me his K2 for service. I spent a good amount of hours
> researching this problem where I was able to reproduce what Barry was
> hearing. It was through his wonderful description of how to produce the
> problem that I was able to reproduce the same issue on a number of K2's
> I have here in the shop including my own personal K2 #5099.
>
> With that said, I must emphasize that the great majority of K2 users
> will not be affected by this issue. There have been reports of chirps or
> pops during tuning in the past. Most were resolved by running CAL PLL
> again and making sure that the bottom cover was installed on the unit
> after plenty of warm up time. This is still the first line of defense
> when dealing with this problem. Unfortunately for Barry, this did not
> solve the issue he was hearing. And while I can explain why the issue
> occurs, I can't really explain why it is worse for some units than
> others except to say that the K2 was designed to use readily available
> through-hole parts with 5% and 10% tolerances and that it's possible
> those tolerances add up in certain circumstances. And, it must be
> remembered that the K2 is a 22 year old design. The fact that this
> design still produces a rig with the performance numbers it has after 22
> years and is still available as a build-able kit is a great tribute to
> Wayne and Eric's vision and implementation.
>
> The issue: audio chirps and pops were being heard while tuning only when
> there were strong signals on the band within +/- 50KHz of the VFO
> frequency being tuned. These chirps were being heard every 5KHz of
> tuning. This happens to be the tuning boundary of the K2 PLL Oscillator.
> In a nutshell, at the 5KHz boundary, the PLL chip was programmed with
> new divide by registers and then the PLL Oscillator was moved to the min
> or max end of its range depending on the direction of tuning. Between
> these two operations was a brief period (a few milliseconds) where there
> was some instability while the closed loop of the PLL circuit settled
> down after the change in boundary. This produced a large voltage spike
> from the output of the PLL chip that caused the integrator circuit
> feeding the VCO varactors to sweep the VCO 50KHz or so in a few
> milliseconds. If there was a large signal in that frequency range, it
> was heard as a chirp or pop. It would be like spinning the VFO knob
> 50KHz in 8 milliseconds. This is why these chirps are not heard when
> there are no signals on the band in the area of tuning.
>
> As I was able to reproduce this issue, I believe in the past, I just
> simply blew off what I heard as atmospheric noise while I was tuning,
> especially on noisier bands like 40m. Barry could really hear it on 20m
> where there was less atmospheric noise but large signals on the band.
> This is especially exacerbated when tuning through the lower part of 20m
> during a contest where strong CW and digital mode signals made this very
> noticeable. Again, most users will not notice this especially if tuning
> slowly through the band. When using a tuning rate of 100Hz or 1KHz, it
> may be more noticeable as you are hitting the 5KHz PLL Osc boundary
> quicker.
>
> As I explained to Barry, I would never have noticed this before he
> explained how to produce it. Now that I know what it is, it drives me
> crazy. And I am not describing this to bring it to light for all of you
> (although I know many of you will try to reproduce it now - sorry). As
> Wayne explained to me, this type of PLL tuning design was fairly popular
> (and cutting edge) at the time and many radios of the time might produce
> similar results.
>
> What I came up with for Barry was a simple one-shot circuit that would
> punch the AGC line of the IF Amp during the 5KHz tuning boundary to
> dampen the volume for about 15ms to prevent the audio chirp. It monitors
> the chip select line of the PLL chip which happens when the process of
> setting the divide by registers is going to occur at the beginning of
> the PLL boundary reset. The pulse dampens the IF Amp long enough to
> allow completion of the boundary reset and prevent any strong signals to
> be heard that may be in the VCO sweep that follows.
>
> Again, the vast majority of users will not notice this issue, and as I
> mentioned, it may be at different intensities on a per unit basis. I am
> trying to develop a very small SMD version of this one-shot circuit for
> Barry to test out. This is not a documented mod as yet and has not been
> approved by Wayne and Eric in any manner except for experimental
> purposes. I just wanted to explain where things are at before this
> conversation became speculative or confrontational.
>
> I will be happy to answer any questions that may come up.
>
> 73,
> Dave W8FGU
>
> ------ Original Message ------
> From: "Macy monkeys" <macymonkeys at charter.net>
> To: elecraft at mailman.qth.net
> Sent: 11/21/2020 9:53:35 AM
> Subject: Re: [Elecraft] K2 purchase considered
>
> >
> >Me neither. #586.
> >
> >John K7FD
> >
> >>  On Nov 20, 2020, at 10:13 PM, Vic Rosenthal <k2vco.vic at gmail.com>
> wrote:
> >>
> >>  Strange. I have K2 #725, which received various mods over the years,
> but I never noticed anything like a loud pop, nor do I recall a mod for it.
> >>
> >>  Victor 4X6GP
> >>
> >>>  On 21 Nov 2020, at 4:41, barry halterman <kthreebo at gmail.com> wrote:
> >>>
> >>>  I will throw my two cents in on this. Quite frankly, I do not see
> how a K2
> >>>  got the reviews it did over the years. I put one together in July to
> do
> >>>  something during lock down. After assembly, which was really a
> pleasure,
> >>>  and in two or three weeks after, I noticed a disturbing pop when
> tuning
> >>>  around strong cw stations. The s meter would jump to maximum signal
> >>>  strength and my ears took a beating with the loud pop!
> >>>  The rig went back to Elecraft for evaluation and I was told with this
> type
> >>>  of PLL circuit design, this is the nature of the beast. Having known
> this
> >>>  irritating pop is nature of the beast, I would have saved my money!!
> >>>  I want to say that Elecraft made a modification to help with the
> strong
> >>>  pops and I am very thankful for that and the the terrific service,
> but the
> >>>  pops are a big annoyance to me even with the suppressor.
> >>>  I still am evaluating if I want to keep this thing or put it up for
> sale.
> >>>  K3bo
> >>>
> >>>>  On Fri, Nov 20, 2020, 9:11 PM Macy monkeys <macymonkeys at charter.net>
> wrote:
> >>>>
> >>>>  Agree. I have had a parade of 'better' rigs come and go through the
> >>>>  shack...but my K2 built over 20 years ago is still here.
> >>>>
> >>>>  John K7FD
> >>>>
> >>>>>>  On Nov 20, 2020, at 5:41 PM, Robert G Strickland via Elecraft <
> >>>>>elecraft at mailman.qth.net> wrote:
> >>>>>
> >>>>>  John...
> >>>>>
> >>>>>  Jim has the resume to back up his opinion(s) which I do not have.
> His
> >>>>  view point always merits serious consideration. For myself, building
> the K2
> >>>>  was/is one of the "peak experiences" I have enjoyed as an amateur
> radio
> >>>>  operator. While I now use a K3s - and it is a "better" radio - I have
> >>>>  continued to use the K2 regularly over the years. I never fail to
> smile
> >>>>  when it powers up, and the two of us go on the radio journey of the
> moment.
> >>>>  It is my go-to radio for field day. When I bought it there were no
> other
> >>>>  options, while today, the KX2/3, K3/s, K4 are all excellent radios
> that
> >>>>  should be considered; you can't go wrong with any of them. That said
> and
> >>>>  speaking for myself, I would sell any of the "better" radios in my
> >>>>  possession before parting with my K2. When you go on to better and
> better
> >>>>  rigs, you'll never regret the time spent with the K2. This reads
> like a
> >>>>  "testimonial," and I suppose that it is. No offense to anyone meant.
> Just
> >>>>  one ham's opinion.
> >>>>>
> >>>>>  ...robert
> >>>>>
> >>>>>
> >>>>>  11/20/2020 06:54 PM, Jim Brown wrote:
> >>>>>>>  On 11/20/2020 10:07 AM, John Daws wrote:
> >>>>>>>  Am really tempted to get a K2 to use alongside the above- I have
> an
> >>>>>>>  experienced builder here in the UK.
> >>>>>>>
> >>>>>>>
> >>>>>>>  Everything I have read about the K2 excites me!!
> >>>>>>
> >>>>>>  Most of the fun of the K2 is in the building. The newer rigs (K3,
> K3S,
> >>>>>>  KX3, K4) are better radios.
> >>>>>>
> >>>>>>  73, Jim K9YC
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>  ______________________________________________________________
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> >>>>>
> >>>>>  --
> >>>>>  Robert G Strickland, PhD ABPH - KE2WY
> >>>>>rcrgs at verizon.net.usa
> >>>>>  Syracuse, New York, USA
> >>>>>
> >>>>>
> >>>>>  ______________________________________________________________
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