I downloaded the software, and found I could get my SSB OPT1 filter looking 
great until I turned on the AGC in USB!

Well I did solve it. It was a poorly aligned L34 causing the problem. I had 
read on this list that L34 was very broad and did not do much. Not at all true!

Now turning AGC off and on does what you would expect. I am going to work 
though with the new software to better tweak things!


Chuck K8LBH

> On Jan 14, 2020, at 2:52 PM, Don Wilhelm <> wrote:
> 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 (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 
> 73,
> Don W3FPR
> On 1/14/2020 1:22 PM, 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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