[Elecraft] Re: KX1 IF filter tuning?

[Phil Wheeler]

Jeff,

I have not tested mine nor noticed the issue you mention (can't find my 
noise gen!).  But I would expect that the center freq would be in the 
500-700 Hz range as the filter is narrowed, since that the the sidetone 
range.

Keep us posted re any new results.  Assuming I find the N-Gen, I might 
have a chance to test my KX1 on Wed (earliest); but I also need to 
install Gram on the current laptop.  Perhaps someone else (e.g., N0SS) 
will have a chance sooner.

73, Phil

Jeff Stai WK6I wrote:

>At 05:16 PM 12/8/2003, Wayne Burdick wrote:
>
>
>  
>
>>Jeff Stai WK6I wrote:
>>    
>>
>>>OK, here goes... has anyone put their KX1 on to Spectrogram to look at the filter shape? I have...
>>>      
>>>
>>Hi Jeff,
>>
>>The KX1's filter passband is a compromise to allow varactor tuning over a wide
>>range. Since some ripple is unavoidable in this case, adjustment of the FILTER
>>control may occasionaly be desireable to optimize for a particular signal pitch.
>>Of course the effect is lessened by the KX1's AGC when signals and noise are at
>>high levels.
>>    
>>
>
>hi Wayne - I understand that a filter can have passband ripple, but in this 
>case I seem to be experiencing 10-15dB of "ripple", and the main "trough" is 
>right in the middle of recommended 600Hz tone.
>
>I'm sorry, that just doesn't seem right. 
>
>I realize this filter is not as capable as the K2 filter, but I don't have 
>anything like this kind of ripple on my K2s.
>
>I guess I am really not understanding what you wrote above - normally, I 
>would vary the FILTER control to narrow the IF BW to focus on the signal I 
>am receiving and eliminate QRM and QRN around it. I would zero beat with the 
>other station at 600Hz since that is the BFO offset. If I understand the 
>above statement, after zero-beating I will need to use the RIT while 
>changing the FILTER to put the received tone into the filter passband...? (I 
>am not able to run the test now, since I spent most of today recovering from 
>a Windows crash, but I recall the filter was many dB down at 600Hz at narrow 
>settings.)
>
>
>  
>
>>If you weren't interested in wider bandwidths at all, you could select a
>>different termination impedance, although I haven't experimented with this. I
>>wouldn't recommend doing this without fully re-testing the passband at all
>>settings of the FILTER control.
>>    
>>
>
>It would be fair to say that I could live with poorer performance at wider 
>BWs, and focus on sub-1000Hz for CW - I could even imagine adding a little 
>switch for the two BW ranges if I was interested enough.
>
>Would I be changing R19? Could you suggest some ranges to try?
>
>thanks! - jeff wk6i
>
>  
>


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