Elecraft

K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev

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Linden, Mike (BRC-Hes)

K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev

Once I get to the Stage III alignment on my K2, I plan on using
Spectrogram to align the CW and SSB filters/BFOs. It seems that proper
filter alignment is a juggling act between the following:

1) Proper centering of the signal within the filter's passband: For the most
part, CW should be aligned in the center or the largest peak, SSB should be
aligned for best audio quality (usually with the bottom at about 300Hz).

2) Constant pitch across the different bandwidth filters for a given mode.
In other words, you should hear very little pitch change (<= 20Hz or so) as
you move from the widest filter for a given mode to the narrowest filter for
that same mode.

3) Constant pitch as you switch between USB/LSB on an accurately tuned AM
signal like WWV and constant pitch as you switch between CW and CW-Reverse
on an accurately tuned CW signal.

Is it difficult to satisfy number 3 if you tune the filters with
Spectrogram based on number 1? Has anyone come up with a reliable
methodology for doing this, or is it just something that you pretty much
play with until you are satisfied?

Thanks, Michael N9BDF
K2 #4137

PS The "Amateur Radio Emergency Communications Consistency Act" (HR 1478)
and the "Amateur Radio Spectrum Protection Act" (HR 713 & S. 537) are in
Congress. Please contact your Congressmen to ask for their support of these
bills! See the following ARRL link for details:
http://www.arrl.org/govrelations/ <http://www.arrl.org/govrelations/>

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Ron D'Eau Claire-2

RE: K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev

Hi, Michael!

Criteria 1) is not possible at the wider filter bandwidths without losing
single-signal reception (hearing the signal on only one side of zero beat).
Consider this: you choose a sidetone of 600 Hz. If the filter bandwidth is
2000 Hz and you center the signal in the bandwidth, then the filter will
pass frequencies from 1600 Hz down to zero beat and up to 400 Hz on the
wrong sideband! The better approach is to place the bandpass so that it
never gets closer than about 200 or 300 Hz from zero beat. Filters widths up
to about 1000 Hz can then be centered on the beat frequency. Wider filter
bandwidths will be set off-center as needed.

2) and 3) are limited by the resolution of he digital to analog converters
(DACs)in the K2. When you do the filter alignment, the K2 stores a tuning
voltage value that will put the BFO back on the right frequency each time
you choose a filter setting or switch from normal to CW REV. The DAC's have
a resolution or "resettablity accuracy" of about 30 Hz. That means that you
may hear a 30 Hz difference in beat as you move from one filter setting to
another. You can often reduce the error by having the K2 re-measure and
store the tuning voltage value for a filter setting again until it happens
to hit a value that produces close enough to the right frequency to please
you. It is possible, by pushing a few buttons repeatedly while doing the
alignment to get the filters within 10 or 20 Hz. That includes switching
from one sideband to the other (normal to cw rev) as well as switching from
one filter to another.

Ron AC7AC

-----Original Message-----
Once I get to the Stage III alignment on my K2, I plan on using
Spectrogram to align the CW and SSB filters/BFOs. It seems that proper
filter alignment is a juggling act between the following:

1) Proper centering of the signal within the filter's passband: For the most
part, CW should be aligned in the center or the largest peak, SSB should be
aligned for best audio quality (usually with the bottom at about 300Hz).

2) Constant pitch across the different bandwidth filters for a given mode.
In other words, you should hear very little pitch change (<= 20Hz or so) as
you move from the widest filter for a given mode to the narrowest filter for
that same mode.

3) Constant pitch as you switch between USB/LSB on an accurately tuned AM
signal like WWV and constant pitch as you switch between CW and CW-Reverse
on an accurately tuned CW signal.

Is it difficult to satisfy number 3 if you tune the filters with
Spectrogram based on number 1? Has anyone come up with a reliable
methodology for doing this, or is it just something that you pretty much
play with until you are satisfied?

Thanks, Michael N9BDF
K2 #4137

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Don Brown-4

Re: K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev

In reply to this post by Linden, Mike (BRC-Hes)

Hi

Actually this is fairly easy to do with spectrogram. First use the new method listed on the Elecraft website to make sure C22 is set right. I use the 600 and 500 Hz tones on 10 Mhz WWV to get the tuning right on a 600 and 500 Hz marker in spectrogram. Then go back and forth between TP2 and TP3 to get Khz and Hz to match (ignore the Mhz). Then run Cal PLL. Once the VFO is calibrated I connect the noise generator and set each of the CW filters centered on 600 HZ (or whatever your side tone is). You need to move every one of the filters even if it is good so the firmware will recalculate the offset. The SSB filters should be set so the fall off slope starts at about 300 Hz and drops to the baseline by about 100 hz. Try to get the LSB and USB to look as close to the same as possible. The frequency readings should be close to the range listed in the BFO setting table in the manual. If the frequency is way off you have set the filter on the wrong side of the slope. Move it back in the ball park listed in the table and then center the band pass in spectrogram. As a final test remove the antenna and tune to 4.000 MHz and check the tone of the 4 MHz clock on each CW and CW reverse filter. The tone should not change frequency. Set the VFO to 4.00060 Mhz and check for the same tone on LSB then set the VFO to 3.99940 Mhz and check USB. In all cases you should hear the same 600 hz tone If not then you need to redo one or more of the filters.

Don Brown

----- Original Message -----
From: Linden, Mike (BRC-Hes)<mailto:[hidden email]>
To: [hidden email]<mailto:[hidden email]>
Sent: Tuesday, July 13, 2004 8:16 AM
Subject: [Elecraft] K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev

Once I get to the Stage III alignment on my K2, I plan on using
Spectrogram to align the CW and SSB filters/BFOs. It seems that proper
filter alignment is a juggling act between the following:

1) Proper centering of the signal within the filter's passband: For the most
part, CW should be aligned in the center or the largest peak, SSB should be
aligned for best audio quality (usually with the bottom at about 300Hz).

2) Constant pitch across the different bandwidth filters for a given mode.
In other words, you should hear very little pitch change (<= 20Hz or so) as
you move from the widest filter for a given mode to the narrowest filter for
that same mode.

3) Constant pitch as you switch between USB/LSB on an accurately tuned AM
signal like WWV and constant pitch as you switch between CW and CW-Reverse
on an accurately tuned CW signal.

Is it difficult to satisfy number 3 if you tune the filters with
Spectrogram based on number 1? Has anyone come up with a reliable
methodology for doing this, or is it just something that you pretty much
play with until you are satisfied?

Thanks, Michael N9BDF
K2 #4137

PS The "Amateur Radio Emergency Communications Consistency Act" (HR 1478)
and the "Amateur Radio Spectrum Protection Act" (HR 713 & S. 537) are in
Congress. Please contact your Congressmen to ask for their support of these
bills! See the following ARRL link for details:
http://www.arrl.org/govrelations/<http://www.arrl.org/govrelations/> <http://www.arrl.org/govrelations/<http://www.arrl.org/govrelations/>>

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Elecraft web page: http://www.elecraft.com<http://www.elecraft.com/>
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Don Brown-4

Re: K2 Filter Alignment: more

Hi

MORE

As Ron explained the centering of the filters should only be done on the narrower filters below 1Khz. If you are setting up a wide CW filter or you are using the SSB filter as one of your CW filters (FL1) then you will set it up like the SSB filter with the lower slope starting to roll off at about 300 Hz and the upper slope rolling off at about what ever bandpass you are setting. I usually set the CW filters on a SSB equipped K2 to FL1=OP1 (2500 hz SSB filter), FL2=1000 hz, FL3=500 hz and FL4=200 hz. Setting the narrow filter much below 200 Hz will cause a fall of in receiver gain. If you need a narrower filter than this use the audio filter or DSP. It will get you down to about 80 Hz bandwidth without the loss of gain.

Don Brown

----- Original Message -----
From: Don Brown<mailto:[hidden email]>
To: [hidden email]<mailto:[hidden email]> ; Linden, Mike (BRC-Hes)<mailto:[hidden email]>
Sent: Tuesday, July 13, 2004 9:27 AM
Subject: Re: [Elecraft] K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev

Hi

Actually this is fairly easy to do with spectrogram. First use the new method listed on the Elecraft website to make sure C22 is set right. I use the 600 and 500 Hz tones on 10 Mhz WWV to get the tuning right on a 600 and 500 Hz marker in spectrogram. Then go back and forth between TP2 and TP3 to get Khz and Hz to match (ignore the Mhz). Then run Cal PLL. Once the VFO is calibrated I connect the noise generator and set each of the CW filters centered on 600 HZ (or whatever your side tone is). You need to move every one of the filters even if it is good so the firmware will recalculate the offset. The SSB filters should be set so the fall off slope starts at about 300 Hz and drops to the baseline by about 100 hz. Try to get the LSB and USB to look as close to the same as possible. The frequency readings should be close to the range listed in the BFO setting table in the manual. If the frequency is way off you have set the filter on the wrong side of the slope. Move it back in the ball park listed in the table and then center the band pass in spectrogram. As a final test remove the antenna and tune to 4.000 MHz and check the tone of the 4 MHz clock on each CW and CW reverse filter. The tone should not change frequency. Set the VFO to 4.00060 Mhz and check for the same tone on LSB then set the VFO to 3.99940 Mhz and check USB. In all cases you should hear the same 600 hz tone If not then you need to redo one or more of the filters.

Don Brown

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Don Wilhelm-2

Re: K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev

In reply to this post by Linden, Mike (BRC-Hes)

Michael,

Actually there is no real connection between hearing the same pitch when
switching between LSB and USB and proper filter alignment like there is with
CW and CWr.

The SSB passband will pass a wide range of tones even if the passband is
severely mis-aligned. The only observation one can make by switching
between USB and LSB is to verify that the displayed frequency is really the
frequency that the display indicates - and that will only be valid after the
alignment is complete.

The way to set things up properly is to use a wideband noise generator and
Spectrogram to set the filter/BFO relationships. Then fine tune the
reference oscillator (I prefer the N6KR method - which is now documented on
the Elecraft website, and is now called the "K2 C22 Adjust App Note"), run
CAL PLL to set the VFO and then walk through all BFO settings in CAL FIL
changing them up one notch then back down which forces the K2 to re-write
the BFO values into the EEPROM. The BFO values must be re-written whenever
the reference oscillator setting is changed to produce a good dial
calibration reading.

After you have done that you can tune in WWV and verify that you are on the
correct frequency by switching from LSB to USB listening for the same tone
(the tone that they are transmitting - not a tone produced by a beat with
the carrier).

For more detailed information on the entire dial calibration procedure, see
the article on my website www.qsl.net/w3fpr.

73,
Don W3FPR

----- Original Message -----

>
> 3) Constant pitch as you switch between USB/LSB on an accurately tuned AM
> signal like WWV and constant pitch as you switch between CW and CW-Reverse
> on an accurately tuned CW signal.
>
> Is it difficult to satisfy number 3 if you tune the filters with
> Spectrogram based on number 1? Has anyone come up with a reliable
> methodology for doing this, or is it just something that you pretty much
> play with until you are satisfied?
>
> Thanks, Michael N9BDF
> K2 #4137
>

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Rich Lentz

RE: K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev

>> Actually there is no real connection between hearing the same pitch when
switching between LSB and USB and proper filter alignment like there is with
CW and CWr.

This explanation has me confused. The description on page 102 (Rev c) gives
me the impression that the K2 shifts the BFO relative to the passband for
BOTH USB and CWR (17 M & below). This also agrees with my observations.

I have found that I have had to change the passband by one or to digits to
get a good compromise between desired passband and alignment of received
frequencies, that is W1AW and WWV does not move as you select different
XFIL. I do not have this problem on CW and LSB (again, 17 M & below) as the
BFO numbers (See table 8-1) are all the same. This BFO number [for CW and
LSB (again, 17 M & below)] also agrees with the number you get using the
N6KR method. For weak signal digital modes where I want to use the XTAL
filters I will use LSB for 17 and below and USB on 15 and above to minimize
this shift and the resultant "signal creep" from the other end tracking my
shift.

There is an Excel Spread Sheet that helps you get in the ballpark for these
BFO settings on the Elecraft Web Page.

Rich
KE0X

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Amanda25650

Re: K2 Filter Alignment: USB vs. LSB, CW vs. CW-Rev

In reply to this post by Linden, Mike (BRC-Hes)