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

[Peter Hall]

Wes

Kenwood have delivered a very credible IMD performance from the new TS-890S and, indeed, even the TS-590s (especially the SG) are considerably better than the Elecraft offerings. All are 12 V radios, of course.  I use a TS-890S with a KPA1500 and, while the combination is poorer in IMD terms than my 50-yo Collins S-line, it's a great deal better than many contemporary offerings.  I don't anticipate parting with the TS-890S any time soon but, all things being equal, regard a K4 with good pre-distortion implementation as a deal maker in the not too distant future.  Indeed, I might have waited for a K4 this time around, barring the shenanigans surrounding the K4 forum discussion and announcement.

Peter, VK6HP. 

-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Wes
Sent: Friday, 30 August 2019 1:10 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3--Too much ALC creates energy on opposite sideband?

Conrad and I have corresponded about this in the past.

He is absolutely correct in worrying about the IMD performance of the K4.  I bought my K3S after being disappointed with the K3 TX IMD and thinking that the FETs would be better.  How wrong I was.  IMD was no improvement and reliability was awful.  At 50 VDC, they no doubt would be better but as long as Elecraft clings to "12-volt" radios, I'm afraid this will persist.

Wes  N7WS


On 8/29/2019 5:04 AM, Conrad PA5Y wrote:
> 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
>

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