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K2 Filter Alignment Using Spectrogram 5.17

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K2 Filter Alignment Procedures Using Spectrogram v5.17

rev. 2.2 02/25/2006

NOTE: This document includes instructions for both CW and SSB filter alignment INSTALLATION AND PRE-SETTING OF SPECTROGRAM 5.17 CONTROLS

1) Install Spectrogram v.5.17 onto your Hard drive, in its own subdirectory ('folder' for those of us who are "Windows-challenged"). I named my subdir C:\Spectrogram, but of course, you may use whatever name you wish. 2) Prepare a jumper cable to go between your K2 and PC's sound card. Generally, this will be a 2-wire cable connected to the TIP and SLEEVE (ring is not used) of two 1/8" STEREO phone plugs. A attach the jumper cable from either the K2 speaker (preferred) or headphone output to your sound card input. MIC input may work better than LINE input, but try each and use the one that gives the best drive to the sound card. 4) Start Spectrogram running. If you have not created an icon on your desktop through which to start Spectrogram, you can always start it via the RUN command on your Start Bar. 5) Press [F3] to start a spectral scan ([Esc] to STOP a scan). The first screen presented to you is the Spectrogram Scan Input (setup) screen.

Figure 1: Spectrogram v.5.17 Scan Input (setup) Screen for CW filter alignment 6) Set the following parameters: (others may work as well, or better, these will help you to get started) Sample Characteristics Sample Rate: 11kHz Resolution: 16 bit Type: MONO

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Display Characteristics Display Type: LINE Channels: N/A Scale (dB): 60 Palette: BW (for black lines on white background) Scroll Memory: N/A Time Scale: 20mS Cursor Offset: 0 Hz Frequency Analysis Freq Scale: Linear FFT Size: 1024 Freq Resolution: 10.8Hz (slider to left edge) Band (Hz): 0 - 2756 Average Count: 60 (Start with this value, you may increase it to over 100. Increasing the value will cause the display to take longer to `build'. Lowering the value will cause the display to appear more `noisy'.) Pitch Detector: OFF Recording Enable: OFF 7) Press Enter to start the Spectrogram software running and displaying the spectrum of the audio input.

8) At the far right edge of the Spectrogram window, there is a vertical scroll bar. Click-hold and drag the scroll bar to the top of the window 9) If you are using ambient band noise, adjust the AF Gain on the K2 to the point where you have a spectral display which extends at least halfway up the left hand scale (between ­50dB and ­40dB). If you are using a noise generator, turn it on and adjust the AF Gain to a level of -40dB to -30dB. Excessive drive from the K2 can cause erroneous display readings. 10) At this point, click on the Pointers menu option and select BLACK CROSS.

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11) Again, click on the Pointers menu option. Select FREQ MARK and set Marker 1 to the numeric value which matches the SIDETONE frequency you have selected for your K2 (the sidetone you wish to hear when you are receiving CW). I use 600Hz for this illustration, but everyone's ear is a little different, select the sidetone most pleasing to your ear. Press Enter to return to Spectrogram.

FREQ MARK = 600 Hz

Disregard this Peak. It is an artifact of the sound card input circuit and NOT relevant to your adjustments

PRE-ALIGNMENT OF L34

The following alignment procedure comes courtesy of Rich Lentz (KEØX) and is strongly recommended. Give it a try. If you find that you cannot improve upon your present settings, then nothing is lost, however, this method of setting L34 should result in many users being able find the point of best signal-to-noise ratio for L34. If you are questioning how to best adjust L34 - "I.F. Amplifier Alignment" section of "Alignment and Test Part II," I suggest using Spectrogram and the following procedure. Follow the instructions for "I.F. Amplifier Alignment. You will notice some noise spread across the display spectrum. Make sure the XFIL is set for FL-1 OP-1 (or your widest available filter passband if the KSB2 is not installed). Now continue to adjust L34 for a compromise of the lowest displayed noise and the highest level of the tone. You will find a point where the noise is almost non-existent, while the tone remains strong. Even though I had adjusted this to what I thought was the best by "ear," after using this method and then readjusting the AGC threshold. I was amazed at the difference in sensitivity and audio level.

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CW ALIGNMENT PROCEDURES

It will be assumed that you have already performed the RX alignment procedures in the K2 manual, that you have already selected the CW filter bandwidth (BW) for all filters you wish to use for CW reception, AND that you have (more or less) properly placed the BFO settings on the correct side of each of the CW the filters (CW Normal and CW Reverse)... not necessarily exactly where you want them, but close, using the directions provided in the K2 FILTER Alignment section of the manual. These steps are ESSENTIAL to help ensure that you set the filters correctly.

Ensure that your FCTR probe in connected to TP2 in the K2.

If you have not already performed the steps outlined above, DO SO NOW, before continuing.

DISABLING AF FILTERING IN THE K2

NOTE: If you have installed the KAF2 AF filter, be sure to set AFIL to OFF (for the KDSP2, set it to BYPASS before you proceed to set the filters. If you have the KDSP2 AF DSP filter installed, proceed as follows to place the DSP into BYPASS mode: Go to the DSP display by tapping [DISPLAY] . If the denoiser is active, tap [BAND+] to kill it. Press the [RCL]Rbutton. You should see the Filter menu display something similar to:

Press the [RCL]Rbutton a second time. You should see the Filter menu display:

If you tap BAND-, you will hear a change in audio and you will see

Simply tap [BAND+], and you will return to DSP ON.

But DO NOT enable DSP until alignment is completed.

Continued on next page.

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READ THIS ENTIRE SECTION (CW) OF DOCUMENT COMPLETELY one time, then return to step 1 and proceed with the alignment.

These instructions assume that you have your filter bandwidths set to run from wide to narrow. If the order of your bandwidths is reversed, you may wish to begin alignment with a filter selection other than FL1. The ORDER in which you select the filters is NOT critical, however, the order in which the steps are performed is critical. When aligning the K2 CW filters for best reception, it is essential that the BFO be properly positioned within the passband of the CW filter. This means that not only must the received signal be centered within the filter passband, but that it also is positioned on the proper side of the CW filter passband. First, a double-check to confirm BFO positioning within the filter: 1)

Ensure that your FCTR probe in connected to TP2 in the K2.

2) Turn the K2 on, select the CW (Normal) mode, and tune to an empty spot on a band between 1.8 MHz and 18 MHz (preferably the 7 MHz band) where some background noise (but no signals) can be heard. You must have some type of an antenna (or a noise generator) connected to the ANT input of the K2 in order to obtain sufficient noise for the Spectrogram alignment. 3) On the K2, tap [MENU] and use [Band+] or [Band-] to scroll through the setting options, shown on the left side of the display, until the CAL option is displayed. Press-hold [MENU] until the cursor shifts to the right side of the display and then use [Band+] or [Band-] to scroll through the setting options on the right side of the display until the FIL option is displayed. Press-hold [MENU] until the display indicates a value of FLn xxx, where `n' is a number 1 - 4. 4) Tap [Xfil] until your widest BW filter is selected (as indicated by the 'xxx' decimal value on the right side of the LCD display). At this point, if you wish, you may rotate the VFO knob to change and set the desired bandwidth for the selected CW filter. Repeat this step, selecting each successive filter, until you have confirmed that all filter bandwidths are set properly. 5) Tap [Band-] to switch to the BFO (BFn) display. You should now see a 3-digit numeric value between '000' and '255'. This is the BFO frequency value which is currently programmed into the Digital-To-Analog Converter (DAC) for the selected CW filter and filter bandwidth. 6) Using the VFO knob, set the DAC count to read "000" on the LCD display. This gives you a starting point. 7) Turn the VFO knob clockwise (increasing the 3-digit DAC value) until you reach an indicated "255" on the display. As you tune from "000" to "255", you will hear the 'tone' of the background noise go from a fairly high pitch, down to a low pitch, and then back up to a high pitch again. RECORD (on paper) the FLx selection and the DAC value for the point at which the background noise is at it's LOWEST pitch. This marks the CENTER of the filter passband for this filter bandwidth selection. Repeat this step for each of the remaining FLx selections. Note that as the filter bandwidth decreases, the DAC value will also decrease. Be sure to record both the FLx selection and the DAC value for each filter bandwidth. If you are attempting to align filters for the CW (normal) mode (and on 1.8 MHz thru 18 MHz), all 3-digit DAC counts must be lower than the DAC count you recorded for the filter center. If you are aligning the CW REV filters, all 3-digit counts must be above the DAC filter center count. Depending upon which filter mode you are setting, if the DAC count for that mode (and that specific filter) is NOT properly above or below filter center, all you need to do is to adjust the VFO knob to cause the BFO

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(and the DAC count) to shift to the other side of the DAC filter center count, then proceed with fine tuning of the BFO setting, using Spectrogram. 8) If you have not left the CAL FIL menu, proceed to step 8, below. On the K2, tap [MENU] and use [Band+] or [Band-] to scroll through the setting options on the left side of the display until the CAL option is displayed. Press-hold [MENU] until the cursor shifts to the right side of the display and then use [Band+] or [Band-] to scroll through the setting options on the right side of the display until the FIL option is displayed. Press-hold [MENU] until the display indicates a value of FLn, where `n' is a number 1 - 4. 9) Tap [Xfil] until your widest BW filter is selected (indicated by the value on the right side of the LCD display). 10) Tap [Band-] to switch to the BFO (BFn xxx) display. 11) Refer to Figures 2 & 3, below, for an approximation of what you may now see on your Spectrogram display, these examples are for the CW Normal mode and a requested bandwidth (BW) of 1.8kHz. Adjust the AF Gain on your K2 to allow the display trace to run between the ­20dB and ­40dB marks on the Spectrogram display. This ensures adequate drive but will not overdrive the sound card input. Note: In the graphic alignment examples which follow, I state that the example illustrates a filter which is `more or less' properly tuned. I do so because, while the filter may be tuned as closely as possible to the setting you wish to attain, the +/-20Hz ambiguity of the BFO tuning steps may not allow you to adjust the setting more precisely. Thus the `accuracy' of the example is a matter of the opinion of the individual user.

Figure 2 ­ CW Normal, 1.8 kHz BW, tuned too low within the filter bandpass. Note: In the example above, even though you cannot see it, the bass response from the filter is being 'rolled-off' by the lack of low frequency response of the K2's audio amplifier, rather than being rolled off by the filter itself.

Figure 3 ­ CW Normal, 1.8 kHz BW, tuned too high within the filter bandpass.

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12) Adjust the VFO knob (which now adjusts the BFO frequency) to move the lowest frequency peak of the spectrum display until it is centered on the vertical Freq (sidetone) marker as shown below in Figure 4. Note: As illustrated below, a bandwidth (BW) greater than 1.0 kHz may demonstrate multiple peaks. If given a choice, select the highest peak which allows the bottom of the display to remain well above the 0 Hz mark. Narrower BWs will generally not show multiple peaks.

Figure 4 ­ CW Normal, 1.8 kHz BW, more or less properly tuned. Note: Even though this filter bandwidth exhibits another 'peak' to the left of the peak which has been selected, the second (and much higher) peak was chosen because it allows the signals below it to be heard and to NOT be rolled off within the K2's AF amp. 13) Tap [Xfil] to switch to the next filter selection. Tapping [Xfil] at this point will not only change to the next filter selection, it will also SAVE the settings you just selected for the current filter.

Example 5 ­ CW Normal, 1.0 kHz BW, more or less properly tuned. 14) Repeat steps 11 & 12 for each remaining filter selection. See Figures 5 - 7, below, for examples of properly tuned 1.0 kHz, 400 Hz & 100 Hz filters

Figure 6 - CW Normal, 400 Hz BW, more or less properly tuned.

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Figure 7 ­ CW Normal, 100 Hz BW, more or less properly tuned. 15) When tapping [Xfil] returns you to your first filter selection, press-hold the [CW RV] button to select the CW ReVerse filters. Repeat steps 11 - 13 for these filter selections, except that you may NOT be able to select the highest amplitude peak for the widest CW REV BW setting without ending up with the BFO somewhere within the passband of the crystal filter. As a result, I suggest you select a lower frequency peak, even though it may not be the highest peak. At wide bandwidths, this should not cause a significant tuning problem and it will help to ensure that your BFO is outside the skirts of the crystal filter. All other selected filter bandwidths should tune pretty much identically to those set for the CW Normal filters, except that all CW REV BFO values will be above the DAC value for filter center. 16) Once all the filters have been set and you have tapped [Xfil] one last time to save the final setting, I would suggest that you review each filter's setting, to confirm that it is set properly (BFO above/below filter center, depending upon the CW sideband selected). Then tap [MENU] to return to normal K2 operation. Representative BFO Settings (for comparison and reference only) A bit earlier, I noted that, when aligning your filters on 160M thru 17M, all of the BFO DAC/Freq. values for the CW Normal mode should be below the value for filter center of that bandwith step and that all values for CW REVerse should be above each filter's center. Presented below are some representative values taken from my K2. Remember that each K2's BFO will run at a slightly different frequency range, so although your values may not exactly match those shown below, they should still follow the general trend. Measurements taken on the 40M (7.0 MHz) band. Bandwidth (Khz) 1.8 1.0 0.4 0.1 Filter Center DAC / Freq. 162 140 133 131 4914.38 4913.86 4913.72 4913.69 CW Normal DAC / Freq. 117 094 076 072 4913.49 4913.24 4913.12 4913.10 CW REVerse DAC / Freq. 187 154 160 159 4915.15 4914.44 4914.33 4914.30

Note that the filter center frequency will change (lower in frequency) as the bandwidth is narrowed. This is because, when the bandwidth of the K2's variable CW filter is made more narrow, only the upper end of the passband moves (downward) in frequency. The lower end of the passband remains at essentially the same frequency. You are done! If you previously turned your audio filter (KAF2 or KDSP2) off, or took it out of the line, AND if you are NOT going to perform the SSB (filter alignment) now is the time to turn it back on _______________________________ A few parting shots... Remember... while all filter selections should now appear to be relatively close to each, with regard to the tone

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you hear from the received station as you cycle through each filter, the received tones may not be identical. There is a chance that the received tones can be off as much as +/-20Hz as you cycle through the filters. This does NOT mean that you have done anything wrong, just that there is the possibility of a frequency step disparity brought on by the counting limitations of the digital-to-analog converters (DAC) used in the rig. Regardless, the received tones should be quite close together as you step through the available filter settings. However, if you find that you have one (or more) filter selections which, when selected, require you to retune the VFO more than 20Hz to properly center the received signal (especially if you must tune 1kHz or more), this is an indication that the BFO for one or more of the filter selections is set to the opposite side of the filter and should be readjusted to place it on the correct side of the filter. Finally, remember that the tonal difference of received signals when switching between CW (normal) and CW REV is not only dependent upon the DAC, but also upon how well you have managed to zero beat the received signal against your sidetone. A small offset to one side or the other of the sidetone frequency will be reflected by an equal and opposite offset when you switch from one sideband to the other (CWN to CWR). Enjoy. Tom Hammond NØSS nØ[email protected] the "Ø" is a ZERO, not an `oh'

SSB FILTER ALIGNMENT INSTRUCTIONS FOLLOW ON THE NEXT PAGE

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Using Spectrogram v5.17 to Align The K2's SSB Filters

Before aligning the xtal. filters, if the KAF2/KDSP2 filter is installed, BE SURE to:

1) Perform DISABLING AF FILTERING IN THE K2 as described on page 4 of this document. 2) Also ensure that your FCTR probe in connected to TP2 in the K2.

NOTE: If you have not already done so, perform the pre-alignment of L34 as described on page 2 of this document, AND perform the CW filter alignment BEFORE you proceed with the alignment of the SSB filters. SPECTROGRAM v5.17 SETUP & K2 SSB ALIGNMENT PROCEDURE

1) Install Spectrogram v5.17 onto your PC according to the SETUP instructions on page 1 of this document. 2) Turn the K2 on, connect your K2's speaker output to the MIC INPUT of your PC's sound card via an appropriate jumper cable, and tune to a band (preferably 40M, but any band 160M thru 17M is satisfactory) which exhibits a moderate amount of background noise, but NO specific received signals (or connect the output of an antenna noise bridge, or a broadband noise generator to the ANT jack on your K2). Set the K2 to LSB and FL1 (OPT1 for the SSB option). 3)Start the SPECTROGRAM program running on your PC. Press [F3] to start a spectral scan and [Esc] to stop scanning. Note that when Spectrogram starts, you are presented with a setup screen similar to that shown in Figure 1 (below). 4) Adjust the default Spectrogram setup parameters to match those shown in Figure 1. If you prefer to see a white background on the screen, as in the examples to follow, set Palette to BW instead of CB. 5) Press <Enter> or click <OK> to start Spectrogram running. 6) Once Spectrogram is running, click on Pointers | Freq Mark then set Marker 1 to 300Hz, and Marker 3 to 2500Hz. These are the points I've chosen, you may select others if you see fit. These worked fine for me.

Figure 1: Spectrogram v.5.17 Scan Input (setup) Screen for SSB filter alignment

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7) If your K2 is providing sufficient audio for Spectrogram (not much is required, try to NOT overdrive the audio input to your sound card), in a few seconds you should begin to see a trace of the audio output of the K2. See Figure 2 below). This spectrum display represents the filter response of the K2 in SSB mode for the selected filter. Adjust the AF Gain on the K2 to provide a display no higher than -30dB.

Figure 2 - Spectrogram of a (more or less) properly tuned 40M LSB signal using the OP1 (SSB) filter NOTE: Ripple in the passband (the slow up/down wave part, not the jagged part, that's just noise), and roll-off of the filter traces depicted in this document seems to be representative of all K2s. All examples shown were made using the K2 SSB Option filter, with C180 (RF Board) removed. The ripple and roll-off are both more pronounced if only the CW filter is used for SSB reception. As of June 2000, a mod is available for 'flattening out' the passband and significantly reducing the rollnd off of the K2 SSB Option filter. Look for the "K2 2 Xfil SSB Filter Mod". This mod is well worth the effort to add. I believe this mod is now INCLUDED on all K2s from serial number 3000 on.

NOTE:

8) If the trace displayed on the screen appears to be more like that shown on Figure 3 (below), then the BFO is set too close to the center of the filter, and audio response will be probably be much too bassy.

Figure 3 - Spectrogram of an improperly tuned 40M LSB signal (too low-pitched) If this is the case, on the K2, select MENU | CAL | FIL and then press [Band-] to access the BFO adjustment menu. Turn the VFO dial to cause the trace to move higher on the scale, until it closely approximates that shown in Figure 2. Note that the SSB trace may overlap the upper and lower frequency markers, as in Figure 2. It was my intent to try to get the major portion of the displayed frequency response to be more or less centered WITHIN the two frequency markers. 9) If your trace appears to be more like that shown in Figure 4 (next page), then the BFO is set too far away from the filter center and should be adjusted (using the same method as directed in step 9 above) to move the trace downward on the scale, until it closely approximates that shown in Figure 2. 10) Once you are satisfied with your setting for the BFO for this particular filter bandwidth, press [Xfil] to select the next available Filter bandwidth, and then repeat steps 8 and 9 for this filter as well. Repeat steps 8 through 10 for all remaining filter bandwidths for this mode.

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Figure 4 - Spectrogram of an improperly tuned 40M LSB signal (too high-pitched) 11) Press [Mode] to change to USB (Figure 5) and repeat steps 8 through 10 for all filter bandwidths for this mode as well.

Figure 5 - Spectrogram of a (more or less) properly tuned 40M USB signal using the OP1 (SSB) filter 12) Once you have completed the SSB filter alignment procedures, take time to switch between the LSB and USB modes and note that the response curve of the filter is reversed between the two modes. In LSB mode, lower frequencies have a better frequency response that the higher frequencies, and in USB mode, the higher frequencies have a better response. This helps to account for the fact that (on 17M thru 160M) LSB signals generally 'sound' better than USB signals. Since the oscillator injection (mixing) scheme for the K2 is inverted on the bands 15M thru 10M, USB signals sound better than LSB signals. This completes the alignment of the K2 SSB (OP1) filters using Spectrogram.

REGARDING SETTING UP THE K2'S CW FILTERS FOR SSB RECEPTION The K2's CW filter does not demonstrate as flat a frequency response as that of the SSB Option filter... in fact it will probably show a number of sharp peaks and valleys. As a result you may find that the SSB audio obtained through this filter will be either a bit restricted at the high end or the low end (or both) of the audio spectrum, depending upon band and SSB mode. When setting the CW filter for SSB, proceed in the SAME manner as outlined above, BUT be sure to set the desired bandwidth for each filter before you attempt to set it's BFO. With the more narrow bandwidths, realize that the audio spectrum may not completely fill out the 'marked' audio bandwidth. As a result, it will be up to you to decide whether you wish to emphasize the upper, middle, or lower portions of the audio spectrum available to you.

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Figure 6 - Spectrogram of a 40M LSB signal using the variable CW filter at 2.4kHz B/W

Figure 7 - Spectrogram of a 40M LSB signal using the variable CW filter at 2.1kHz B/W

Figure 8 - Spectrogram of a 40M LSB signal using the variable CW filter at 1.8kHz B/W

REMINDER...!

If you have the KAF2 installed, don't forget to re-enable it, both in MENU, and by setting the IN/OUT switch back to the IN position. If you have the KDSP2 installed, simply tap [BAND+], and you will automatically return to DSP ON mode.

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Representative BFO Settings (for comparison and reference only) Presented below are some representative values taken from my K2. Remember that each K2's BFO will run at a slightly different frequency range, so although your values not exactly match those shown below, they should still follow the general trend. Measurements taken on the 40M (7.0 MHz) band. Bandwidth (Khz) OP1 2.4 2.1 1.8 Filter Center DAC / Freq. 177 183 170 158 4914.84 4915.02 4914.62 4914.28 LSB DAC / Freq. 118 112 097 077 4913.49 4913.42 4913.27 4913.12 USB DAC / Freq. 224 230 216 202 4916.28 4916.43 4916.06 4915.63

Note that the filter center frequency will change (lower in frequency) as the bandwidth is narrowed. This is because, when the bandwidth of the K2's variable CW filter is made more narrow, only the upper end of the passband moves (downward) in frequency. The lower end of the passband remains at essentially the same frequency.

Regarding Spectrogram A current version of Spectrogram (for PC compatibles only) is available from: http://www.visualizationsoftware.com/gram.html However, the more recent releases of this software are no longer shareware and are available for a $45 fee. A 'limited-use' (demonstration) version of Spectrogram also is available from the author. Newer releases of this fine software do not provide any additional features which will make filter alignment better or easier.

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