[Elecraft] Lousy Tx audio reports using K2

[Robert G. Strickland]

Don...

When you cite the "-3 to 6dB point," do you mean to say "-3 to -6dB?" That 
is to say, that the "corner" of the filter response, presumably falling at 
the "-3 to -6dB point" should be positioned at 300cps. Is this a correct 
interpretation of your recommendation? Thanks.

...robert

At 12/21/2007 16:51, Don Wilhelm wrote:
>Eddy,
>
>Since you mentioned a lack of highs, I doubt that the low-frequency 
>response mod will help much, but you certainly can try.
>
>What is more important is the place the low frequency corner of the FL1 
>passband close to 300 Hz.  If you do that, when you tune an SSB signal so 
>it sounds right in your K2, you will transmit on his frequency (because 
>you tuned his voice to fall into the 300 to 2800 kHz range where it sounds 
>best to most ears).  If you OP1 filter is set 100 Hz high or low, then you 
>can still receive by skewing the frequency (you really will not know you 
>are doing that, but it happens that way), but then when you transmit, you 
>do not sound right to the person on the receiving end.
>
>When I set up a K2 that is in here for repair, I listen not only to the 
>received signal, but I listen to a transmitted signal on another 
>receiver.  I have found that the 300 Hz filter corner (-3 to 6 dB point) 
>is the one most important factor in making transmit and receive line up 
>properly.
>
>73,
>Don W3FPR
>
>k6sdw wrote:
>>Good stuff Don!
>>
>>I'm concerning doing the G3RXQ mod to the KSB2 and see if that helps with
>>the low-freq response.
>>
>>73.......
>>
>>
>>
>>Don Wilhelm wrote:
>>
>>>Eddy,
>>>
>>>It is important where you set the audio passband.  Normally, there is no 
>>>lack of high frequency response with the 2.6kHz bandpass.
>>>
>>>Using Spectrogram to set the SSB filters, I normally recommend that you 
>>>set markers at 300 Hz and the filter width plus 200 Hz - or in your 
>>>case, 2800 Hz.  Center the FL1 (OP1) passband between those markers and 
>>>try it out.  With most voices and microphones, those settings are 
>>>correct, and wil work quite well for receive as well.  For FL2, I use 
>>>the variable filter and set it 300 Hz less than FL1 - it is important to 
>>>measure the actual width with Spectrogram since at wide setting the 
>>>numbers shown by the K2 are usually incorrect.  Set the low frequency 
>>>corner of all the SSB filter passbands at 300 Hz to maintain 
>>>intelligibility as the filters are narrowed.
>>>
>>>If you are 'netting' with other hams at a specific frequency, you should 
>>>check your dial calibration - if you are not tuned to the actual 
>>>frequency of the other hams (because your dial calibration is off), it 
>>>could be that your audio is OK, but you are placing your transmit 
>>>frequency a bit high or low.  The K2 Dial Calibration article on my 
>>>website http://w3fpr.qrpradio.com can give you the procedure for 
>>>obtaining good dial calibration.
>>>
>>>If filter alignment as I have outlined does not solve your problem, you 
>>>may have a microphone that is lacking in response at the higher audio 
>>>frequencies, but the MH2 usually has a bit of boost for the highs - you 
>>>might want to see if one of the locals near you has an MH2 that you can 
>>>compare with.
>>>
>>>73,
>>>Don W3FPR
>>>
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Robert G. Strickland PhD ABPH - KE2WY
rcrgs at verizon.net.usa
Syracuse, New York  USA