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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