[Elecraft] K2 / K3 audio - and the K2 fan

[Joe Subich, W4TV]

> The issue could be due to 2 factors: AF distortion and AGC
> properties. K2 has a very sweet AGC. K3 had a very high AF distortion
> level that was mitigated by a series of upgrades ( at least choke and
> DSP board). If you read old messages, there is a message by a Russian
> who looked at initial IMD level (very high) and documented
> improvements by adding large capacitors in several places.

If you bother to put most transceivers - particularly older rigs with
analog IF and product detector - on an audio spectrum analyzer and
feed them a source of broadband RF noise you will find the audio
response has a falling characteristic.  The response falls off between
3 and 6 dB per octave above 1 KHz.  One can accomplish that in the K3
by setting SSB RX EQ to 1600 = -3, 2400 = -5 and 3200 = -6 and by
setting CW RX EQ similarly.

I tend to set both 50 and 100 Hz bands to -16, 200 to -6, 400, 800 & 
1600 to 0, 2400 to -4 and 3200 to -6 as that significantly reduces
both low frequency "rumble" and high frequency "hiss".

The other thing to do to make the K3 less noisy (less hiss) is to
increase the AGC threshold and decrease the AGC Slope so the AGC
system does not "pump up" the background noise.  Careful adjustment
of AGC parameters and RX EQ will result in a very "comfortable"
sounding K3/K3S.

73,

    ... Joe, W4TV

On 6/27/2016 10:19 AM, Ignacy wrote:
> I also feel that K2 is easier to listen to under average conditions than K3.
> My K3 has the DSP board updated.
>
> The issue could be due to 2 factors: AF distortion and AGC properties. K2
> has a very sweet AGC. K3 had a very high AF distortion level that was
> mitigated by a  series of upgrades ( at least choke and DSP board).  If you
> read old messages, there is a message by a Russian who looked at initial IMD
> level (very high) and documented improvements by adding large capacitors in
> several places.
>
> I listened to 10m CW at WPX contest with K3 and SDRPlay, both with good
> speakers. The last one sounded slightly cleaner although SDRPlay would have
> easily overloaded with strong signals. It would be interesting to see
> whether K3S sounds better than K3, perhaps due to a number of small changes.
>
> Ignacy, NO9E
>
>
>
> --
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