[Elecraft] K2 LSB Modulation issue

Don Wilhelm w3fpr at embarqmail.com
Sun Oct 10 18:49:13 EDT 2010


  Michael,

I suspect that the BFO for LSB is not correctly for your KSB2 OP1 filter.
First check to be certain the SSB FL1 is set to OP1.  The BFO frequency 
for LSB using the OP1 filter will be between 4913.48 and 4913.65 
depending on your particular filter center, and the USB BFO will be in 
the vicinity of 4916.5.  You can check with the internal frequency 
counter probe in TP2, enter CAL FIL and tap the BAND- button.

Then go to my website www.w3fpr.com and read part 3 of the article 
dealing with K2 Dial Calibration - that is the section that explains the 
filter setting using Spectrogram.
If you do not have a copy of Spectrogram and or need information about 
how to set it up on your computer, download it from Tom Hammond's 
website www.n0ss.net.

If you have not set up your K2 filters before using Spectrogram, you may 
want to align all your filters.

73,
Don W3FPR


On 10/10/2010 5:36 PM, Michael Jensen wrote:
> Hi all
>
>
>
> I have noticed an issue on my trusty K2 #5111.  Might have been there since
> I build it several years ago or it might have come during the years
>
> The issue are the modulation on LSB. The audio are not very good and do
> sound "funny" Could maybe be described as nasal or some one knowing my voice
> call it "like the audio was being frequency modulated".
>
> USB are ok or at least so much better that no one notices.
>
> There are no difference between running high power or low power and have
> tested using different power supplies.
>
> The reason for going un detected is that I in the past not often was below
> 20 on SSB. When I used 40 or 80 it was mainly PSK but running USB. So no
> issue seen. When I was made aware of the issue I first put the blamed on a
> power supply for my PA as beeing the reason. (the magnetic field issue
> discussed here several years back). Now having tested for that it do not
> seem to be the problem.
>
> Any of you that would have experience or comments on a TX audio issue that
> effect only LSB.
>
>


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