[Elecraft] K3--Too much ALC creates energy on opposite sideband?

[Conrad PA5Y]

I have measured the TX IMD performance of my and 2 other K3S transceivers. In my opinion it is not possible to have anything other than mediocre TX IMD performance from a K3S or a K3 at ANY power level. I am so disappointed with this aspect of the K3S. The  mass market and cheap IC-7300 is better, especially on 6m. In all other respects I am very impressed with the K3S.


The transverter output on 10m when set to 0.5mW has incredibly good IMD performance so the problem is with the 2 PA modules. I have contacted Elecraft and so far they have not offered me a satisfactory solution. I think that I am going to go to the inconvenience of using an external PA on 6m.


The K3S has excellent TX composite noise all ruined by poor TX IMD. I can easily see 19th and 21st order IMD components on 6m in the 90dB dynamic range of my E4406A spectrum analyser - this rather negates the advantage to my neighbours when I'm on SSB. For CW and Digimodes then the K3S is superb. If I was contemplating the purchase of a K4 I would be asking Elecraft about TX IMD from the hopefully new and improved TX amplifier chain.


Not a happy message but it's the truth. Yes I have the latest FW, yes I have tried to reduce the gain from the driver using the settings in the FW yes I maintain the correct voltage on the PA, yes I have late (not the latest) revisions of the driver and final PA. I am using the 2 tone facility so there is no question of external or maladjusted audio non linearity. The fact is that it is poor. I also know what I'm doing.


Poor show Elecraft!


73


Conrad PA5Y


________________________________
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> on behalf of Michael Walker <va3mw at portcredit.net>
Sent: 29 August 2019 04:02
To: Elecraft at mailman.qth.net <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] K3--Too much ALC creates energy on opposite sideband?

Hi Fred  (Skip)

Sadly, many of those are splattering so wide that you can hear them on the
opposite sideband.  Unfortunately, a report of great audio does not mean
great IMD performance.

Don't take this the wrong way, I am not saying you have bad IMD it just
that you can't relate the 2 has being an indicator.

With a good radio and a good waterfall you can see it plain as day.  There
are a few locals (aka here in ve3 land) that I 'watch' routinely with their
top end Yaesu's (5000's) and they sound awesome, but they have the absolute
worst splatter you have ever seen.    One guy on 80M was absolutely
understandable when I listened to him on USB.

Nate, glad you got it figured out.   I'm sure we have all been there (me
included).

73 all, Mike va3mw


On Wed, Aug 28, 2019 at 9:43 PM Nate Bargmann <n0nb at n0nb.us> wrote:

> I think I better take a mea culpa on this one.  One reply in a private
> email asked if I was using and amp and whether I was driving it too
> hard.  Well, some mornings this week I have depending on static levels
> and I operated the KS QSO Party this past weekend and ran 100W.  I
> normally run the amp (ALS-600) with the power setting at 70W.
>
> This is probably just a, "D'oh!" moment.  Yes, the K3 was still set for
> 100W.
>
> Incidentally,  My COMP runs about 2-3 bars on voice peaks and the ALC
> meter is in the 5-7 bars range on peaks as well.
>
> It's a PEBCAK3 issue.  ;-)
>
> --
>
> "The optimist proclaims that we live in the best of all
> possible worlds.  The pessimist fears this is true."
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