[Elecraft] CW Reverse Sideband Suppression Bad Using OP-1

[Don Wilhelm]

Frank,

The BFO frequency listed in the KSB2 manual for CWr is no longer correct (it used to be correct before the SSB filter was widened).  When the OP1 filter is used for CW reception, the BFO values will be quite close to those used for SSB - CW should be close the the LSB value and CWr should be close to the USB value.

When you used Spectrogram, the display likely showed that the passband for the CWr filter crossed over the zero frequency line on the Spectrogram display - that is a sure sign that you will hear both sides of zero beat when using that filter.  Re-adjust the BFO frequency to place the passband entirely on one side of zero - again, set the BFO frequency near the value used for USB (for CWr, increase the K2 display numbers or frequency - if decreased you will end up on the wrong sideband).

In all cases but this one, the BFO frequencies shown in the SSB manual are close to the end values.  The use of Spectrogram to further refine the BFO frequencies in order to shift the passband exactly into the desired audio range is a very desirable step.  If the end values after using Spectrogram are different than those shown in the manual, the values obtained with Spectrogram are the correct ones to use - you may re-mark the values obtained with Spectrogram in your manual for future reference.

If you need further information on the use of Spectrogram as a visual aid to properly positioning the filter passbands, take a look at Step 3 of the K2 Dial Calibration article on my website http://w3fpr.qrpradio.com for information.

73,
Don W3FPR
 

> -----Original Message-----
>  
> I  purchased a one year old K2 #5116.  Its equipped with the KSB2 
> SSB module. 
>  
> I  noticed the filter selection for CW Wide wasn’t set up with 
> OP-1 as per 
> the  
> instructions for the KSB-2.    So I went into the Cal Fil  and 
> set all the 
> BFO  
> settings exactly as per the KSB2 manual to  allow OP-1 to be used 
> in place of 
> FL-1 
> on CW Wide.  Then I used the Spectrogram software to set the 
> filters  exactly 
> as per the instructions.   All the filters tuned up perfectly  . 
> All  went well exact for one thing.    On CW Reverse,  using OP-1,  I can 
> hear 
> both sides of zero beat on the CW signals --- at  the same level. 
>  So with an 
>  S9 
> signal I have to tune through  both sides of zero beat at S9 but  
> only using 
> CW Reverse.   
> e CW Normal using OP-1 has  prefect side band suppression with no  
> sign  of the other side of zero beat.  
> I  can tune CW signals while in either USB or LSB mode and it receives  
> perfectly 
> with no sign of the other side of zero beat.  So SSB suppression  
> on both USB 
> and LSB  appears to be ok.  
> The  only thing that’s not coming up right is while using OP-1 in 
> place of 
> FL-1 on  
> CW  Reverse.   Everything else  appears to be working as it 
> should be in this 
> K2.  
> Anyone have  any ideas on what to look for as the cause?    
> Frank W7IS  
>