K2 Filters Will Not Align Properly

[Howard W. Ashcraft]

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.

PLL Reference Oscillator Range Test

High = 12101.55
Low  =  12088.14
Dif  = 13.44  (Acceptable 9.8 - 15)

VCO Voltage  all greater than 1.5 v, less than 7.5 v.

BFO Test

BFO High = 4917.42  (Acceptable >= 4916.3)
BFO Low  = 4912.34  (Acceptable <= 4912.7)
Range    =    5.08  (Acceptable >= 3.6)

Transmit frequency is +- 10 hz.  However, zero beating a 600hz sidetone against the 7.00 Mhz birdie **appears** to be around 7000.35 Khz.  (I never fully trust zero beating as I am tonally challenged...)

Any ideas??



Howard W. Ashcraft, Jr.
Hanson, Bridgett, Marcus, Vlahos & Rudy
425 Market Street, 26th Fl.
San Francisco, CA 94105

ph:     415.995.5073
fax:    [phone]
e:       [hidden email]




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[Vic K2VCO]

Howard W. Ashcraft wrote:

> 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.

You probably did this, but I'll ask anyway: did you do CAL PLL before
trying to do the CAL FIL?
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[Dan Barker]

 I hope you are not trying to CENTER OP1 on 600 Hz. That's not right. You
want the skirt to fall to zero around 200 Hz (left) and around 3K (right).

There may be nothing wrong at all. If you did center it, you'd have
reception on both sides of zero-beat.

Dan / WG4S / K2 #2456

<snip>
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.
</snip>

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[Don Wilhelm-3]

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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[Howard W. Ashcraft]

Thanks to everyone for their suggestions.  However, it turned out to be a different problem.  For reasons unknown, although possibly linked to the Info 80 messages, the KDSP2 was not disengaging as it should and the first DSP filter was wildly off the mark.  This interfered with setting the crystal filters.

Because I don't have access to the code (and if it isn't in C or C++, I would have difficulty following it), I'm not sure if a communication error could cause the DSP filter to errantly set itself.  Before this all started, the DSP filters were at their default settings.

In any event, once the KDSP2 was properly bypassing, everything fell in line.  I'm beginning to think that the K2 saw me reading K3 specs and threw a snitfit... ;)

Thanks, and 73,

Howard W1WF




-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Sun 6/17/2007 5:35 PM
To: Howard W. Ashcraft
Cc: [hidden email]; [hidden email]
Subject: Re: [Elecraft] K2 Filters Will Not Align Properly
 
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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This communication, including any attachments, is confidential and may be protected by privilege.  If you are not the intended recipient, any use, dissemination, distribution, or copying of this communication is strictly prohibited.  If you have received this communication in error, please immediately notify the sender by telephone or email, and permanently delete all copies, electronic or other, you may have.

To ensure compliance with requirements imposed by the IRS, we inform you that any tax advice contained in this communication (including any attachments) was not intended or written to be used, and cannot be used, for the purpose of (i) avoiding penalties under the Internal Revenue Code or (ii) promoting, marketing or recommending to another party any transaction or matter addressed herein.

The foregoing applies even if this notice is embedded in a message that is forwarded or attached.
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[Howard W. Ashcraft]

Dan,

I should have been more careful when I said "centering around 600hz."  600hz is set at about the first major peak of OP1 and is very close to the spacing you describe.

Thanks and 73,

Howard W1WF

K2/100
KX1



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To ensure compliance with requirements imposed by the IRS, we inform you that any tax advice contained in this communication (including any attachments) was not intended or written to be used, and cannot be used, for the purpose of (i) avoiding penalties under the Internal Revenue Code or (ii) promoting, marketing or recommending to another party any transaction or matter addressed herein.

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