http://elecraft.85.s1.nabble.com/K3-Receiver-Noise-Level-Evaluation-and-Adjustment-tp4187070p4195544.html
setting of 15. No modifications.
of modification.
... Joe, W4TV
> -----Original Message-----
> From:
[hidden email]
> [mailto:
[hidden email]] On Behalf Of John Lemay
> Sent: Sunday, December 20, 2009 11:33 AM
> To: 'Sverre Holm (LA3ZA)';
[hidden email]
> Subject: Re: [Elecraft] [K3] K3 Receiver Noise Level --
> Evaluation andAdjustment
>
>
> Hello Sverre
>
> Thanks for putting your spectral analysis on the web page.
> It's very interesting and I decided to do my own test. I used
> Spectrum Laboratory, but it displays similar information to Spectran.
>
> I have deviated from white or pink noise, because most of the
> time we are listening to real signals (or qrm!). I decided to
> inject a signal: I used my K3 and XG1 to perform the test.
> The line out from the K3 was connected to line in on my PC.
>
> With reference to a fundamental audio signal at 0db, a third
> harmonic of this was observed at about -40, and a fifth
> harmonic at around -50dB. The even order harmonics are well
> down in comparison.
>
> I don't know if this is a good result or bad. But it's clear
> to me that if I am listening to a 700Hz CW note, no amount of
> audio roll-off at 4kHz or so is going to change the relative
> levels of those first few harmonics.
>
> Just for fun, I ran the same test using an FT-847. The
> results were very different. Firstly, harmonics were down at
> -55 or better. Secondly, the even order products (2nd and
> 4th) were louder than the odd ones. And lastly, the FT-847
> graph showed several close-in spurious alongside each
> harmonic, which had been completely absent with the K3.
>
> I hope this all makes sense. And apologies if my use of
> technical terms is not spot-on. I'm just an amateur, with no
> training in electronics or radio !
>
> Regards
>
> John G4ZTR
>
>
> -----Original Message-----
> From:
[hidden email]
> [mailto:
[hidden email]] On Behalf Of Sverre
> Holm (LA3ZA)
> Sent: 20 December 2009 13:13
> To:
[hidden email]
> Subject: Re: [Elecraft] [K3] K3 Receiver Noise Level --
> Evaluation and Adjustment
>
>
> Concerning the last few days' discussion of noise and
> artifacts, here is a spectral analysis plot of my K3's
> output:
http://www.qslnet.de/member/la3za/bilder/K3-CW-spectran.jpg>
> First it shows the signal related artifacts in the 10-13 kHz
> range as mentioned by Wayne N6KR below. It also shows line
> noise at approximately every kHz (harmonics of 1.025-1.030
> kHz). The highest of these is at approx 2050 kHz and is at
> about -40 dB relative to the main signal, i.e. at a level of
> about 10^(-40/20) = 0.01 or 1%. Thus these lines could be
> audible and be part of the explanation for the complaints
> about the K3's sound. Apart from the lines, the background is
> down to -60 dB above 2-3 kHz.
>
> It is interesting to note that my spectran plot has discrete
> line noise as opposed to that of G4ILO in his blog from today
> (
http://www.g4ilo.com/blog.html), plot here:
>
http://www.g4ilo.com/uploaded_images/k3freqresponse-736797.gif> . His background noise level is similar to mine.
>
> Could this be due to differences in individual K3's as has
> been hinted to on this list?
>
> My setup is:
> K3 with PRE on at 14.102 MHz, RF gain at max,
> CW with 400 Hz roofing filter and bandwidth set to 400 Hz,
> AGC-F on and with AGC parameters SLP=9, THR=3, I use a lot of
> averaging in Spectran to make the lines more visible as seen
> from the setup info in my plot
>
>
> wayne burdick wrote:
> >
> > This filter rolls off everything at about 4.5
> > kHz, including some low-level AF sampling artifacts from 10-14 kHz
> > that some operators with excellent ears can hear.
> >
>
>
> -----
> Sverre, LA3ZA
>
>
http://www.qslnet.de/member/la3za/K2/mod.html LA3ZA
> Unofficial Guide to K2 modifications
> --
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