Posted by
Don Wilhelm-3 on
Jun 18, 2007; 1:35am
URL: http://elecraft.85.s1.nabble.com/K2-Filters-Will-Not-Align-Properly-tp449275p449277.html
Howard,
Dan Barker's response was likely 'on target'.
It is entirely possible that you have gotten the BFOs set to the wrong
sideband. The CW filters should be at a lower BFO frequency than the
CWr frequencies, and likewise the LSB filters should be lower than the
USB filters.
I suggest that you start over from 'scratch' - download the newest KSB2
manual from the Elecraft website and look at page 20 for the chart of
initial BFO frequencies.
Assume that your OP1 crystals are from the 3.6 set (unless you know the
set designation) and enter 4913.5 in the LSB entry and 4916.3 in the USB
entry and set the BFOs to the frequency indicated in that manual.
Those frequencies should provide a good starting point for your filter
alignment. When using Spectrogram, use a wideband noise generator or
'dead band' noise (turn the preamp on) - attempting to use a single
signal to do the alignment will likely result in confusion and failure.
Take care not to move the passband down through zero frequency on the
Spectrogram display when moving the passband to your chosen sidetone
pitch (that will move it to the wrong sideband).
73,
Don W3FPR
Howard W. Ashcraft wrote:
> After several years of faithful service, my K2/100 (with KDSP2 and KSB2) has developed a perplexing malady. The crystal filter passband will not adjust to center on a 600hz sidetone. As you adjust the filters towards 600 hz using Spectrogram (say OP1), the filter shape degrades and then severely attenuates the signal until NO audio signal is visible on the Spectrogram display. I have repeated the key realignment procedures three times, with identical results.
>
> The long story. The K2/100 generated an Info 080 message that I started diagnosing. The problem "self-corrected" which lead me to believe it was probably a loose connection to the KPA100. Despite lots of opening and closing the case, the problem has not reappeared.
>
> I now have better test equipment than I had when I built the K2 (serial 4357) and it seemed like a good time to realign the transceiver. I did a complete realignment, with minimal changes except a slight kick to the 4Mhz oscillator and a reasonable amount of repeaking of the bandpass filters. So far so good. All of the key tests/parameters were within range.
>
> When I started to set the filters, however, I could not get them within range. As noted above, I can not shift the passband to cover a 600hz sidetone. The filters appear to center around 900-1000 hz. I have attempted to set the filters back to my prior CAL FIL BFO settings, but to no avail.
>
> The following are the test results from this realignment.
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