Posted by
Don Wilhelm on
Jan 14, 2020; 7:52pm
URL: http://elecraft.85.s1.nabble.com/K2-SSB-adapter-problems-tp7657829p7657834.html
Chuck,
Your guess that the BFO is positioned inside the filter passbaad is
likely correct.
Do you have the SSB FL1 filter set to OP1? If not, try that first.
Many times the filter on the RF Board (used for more narrow filter
settings) becomes VERY wide - much wider than indicated by the K2. It
depends on the exact characteristics of the varactors.
If you are using the SSB OP1 filter, then check the capacitors around
the KSB2 filter crystals for proper values. An improper capacitor will
distort the passband shape and can make the passband quite wide.
The best way and more certain way to analyze the problem is to look at
the K2 audio with an audio spectrum analyzer like Spectrogram running on
your computer and band noise fed into the K2 antenna (no signals, just
noise)
You can download Spectrogram from my website www.w3fpr.com (scroll to
near the bottom of the home page to find the local links). If you do
not use Windows, there are audio spectrum analyzers for other operating
systems.
Instructions for setting up Spectrogram 5.17 and using it to align the
filters can be found on Tom Hammond N0SS (SK) website preserved at
http://www.mmccs.com/mmarc/n0ss/k2_filters_using_gram_v5r17.pdf.
73,
Don W3FPR
On 1/14/2020 1:22 PM,
[hidden email] wrote:
> Hello,
>
> I have been working on a new K2 the last couple of months. SN 7927
>
> Yesterday I finished and installed the KSB2 SSB adapter.
>
> I have been mostly listening. All seemed normal with receive on 80 and 40 meters, on LSB.
>
> But, as soon as I go to USB on any band below 21 mhz, or LSB 21 and above, the S meter goes to nearly full scale, and the receiver is desensitized. If I turn off the AGC, the receiver seems to work normally receiving both LSB and USB.
>
> I have checked the BFO values and used the default value of 4916.3 for USB and 4913.5 for LSB.
>
> No setting of the USB BFO seems to solve the issue. I can change the value and drop the S meter with AGC on and hear the Receiver apparently return to normal, but then I can’t tune USB and the number I am using then is close to the LSB value.
>
> Why the receiver works normally with AGC off, but not with AGC on on OP1 filter is puzzling to me. Everything is normal on the K2’s internal filters.
>
> I assume this has something to do with the crystal filter and BFO frequencies, but no idea where to go.
>
> Any ideas would be appreciated.
>
> 73 Chuck K8LBH
>
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