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K2 DSP/Crystal Bandpass Alignment for PSK31

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Bill Strong

K2 DSP/Crystal Bandpass Alignment for PSK31

I am trying to align my 250 hz crystal filter with a 200 hz DSP filter in the middle of the passband of my 2500 hz SSB filter for the purpose of transmitting and receiving PSK-31 in the middle of the 2500 hz filter bandpass.

I have succeeded in moving the crystal filter by changing the bfo setting. It is centered at 1400 in the 2500 bandpass. When I try to narrow the S4 SSB DSP filter it will only narrow to 1000hz spread from 600Hz to 1600 Hz in the bandpass. It seems that the CW DSP filter goes down to 200Hz. I tried the RTTY/DATA mode but was not able to make any sense of what the filters relationship would be when I tried changing the settings.

Any help would be apprciated.

Don Wilhelm-4

Re: K2 DSP/Crystal Bandpass Alignment for PSK31

Bill,

You might want to try the way I set up the RTTY filters.
Of course, I use Spectrogram, and if you are not familiar with that
computer application, take a look at my website www.w3fpr.com and look
in the K2 Dial Calibration article. Part 3 describes how to use
Spectrogram for setting your K2 IF filters.

For RTTY, I normally set FL1 to the OP1 filter (BFOs set the same as for
SSB) to produce the wide waterfall display. FL2 is set to 1.00 width,
FL3 to 700 Hz, and FL4 set to 400 Hz.
I try to align the filters (except for FL1) to a center frequency of
1000 Hz. If the FL4 RTTY (as opposed to RTTYr) cannot be aligned to a
1000 Hz center because of limited BFO range, I use 800 Hz as an alternative.

Once the RTTY filters are set, if a KDSP2 is installed, one must change
the center frequencies in the DSP menu for a center frequency of 1000
(or 800) Hz.

In operating use, one would find a desirable data mode signal in the
waterfall display, then use the VFO knob to move that desired signal to
the vicinity of 1000 (800) Hz, and make contact. If QRM becomes a
problem, lock the transmit frequency in the software application and
engage a more narrow IF filter as required. If the QRM is still a
problem, also use the DSP to produce more narrow skirts on the filtering.

That is how I do it and it works for me - I encourage you to try it and
see if you agree.

Using the RTTY filter set allows you to set the SSBC parameter for data
modes to 1:1 and use a different compression setting for SSB mode.

73,
Don W3FPR

73,
Don W3FPR

Bill Strong wrote:

> I am trying to align my 250 hz crystal filter with a 200 hz DSP filter in the
> middle of the passband of my 2500 hz SSB filter for the purpose of
> transmitting and receiving PSK-31 in the middle of the 2500 hz filter
> bandpass.
>
> I have succeeded in moving the crystal filter by changing the bfo setting.
> It is centered at 1400 in the 2500 bandpass. When I try to narrow the S4 SSB
> DSP filter it will only narrow to 1000hz spread from 600Hz to 1600 Hz in the
> bandpass. It seems that the CW DSP filter goes down to 200Hz. I tried the
> RTTY/DATA mode but was not able to make any sense of what the filters
> relationship would be when I tried changing the settings.
>
> Any help would be apprciated.
>
>
> ------------------------------------------------------------------------
>
>
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Bill Strong

Re: K2 DSP/Crystal Bandpass Alignment for PSK31

Don,

Thank you for your response. I read all of your posts.

I will do as you say. I can see that a center of 1000 Hz would be what I need for use of the 2.2 KSB2 filter for transmitting.

By way of explanation I have been using the waterfall display on DM 780 to set my filters as it seemed to accomplish what I needed. I have been following the K3 PWR Out discussion concerning PSK. I used a watt meter to determine that when transmitting PSK my power out is best over a 1000 Hz range centered on 1400 Hz in the passband of the 2.2 filter (using the waterfall to measure this). That is the reason I was trying to get everything centered on 1400 Hz in the passband of the transmitting filter. It is my understanding that any SSB transmission will go through the KSB2 2.2 filter? so it would be ideal to be centered on it?

Don Wilhelm-4

Re: K2 DSP/Crystal Bandpass Alignment for PSK31

Bill,

The advantage to using a higher center frequency is that there is less
possibility of a 2nd harminic 'ghost' on the data mode signal - caused
by soundcard distortion or other artifacts. With the K2, a center
frequency with a narrow passband may be limited by the BFO range. That
is usually only a problem with RTTY (lsb), but not the normal RTTYr
(usb) while using a narrow filter width (500 Hz or less). Typical
operation with data modes use USB, so the problem is minimized (or
non-existant) in normal operation.

73,
Don W3FPR

Bill Strong wrote:

> Don,
>
> Thank you for your response. I read all of your posts.
>
> I will do as you say. I can see that a center of 1000 Hz would be what I
> need for use of the 2.2 KSB2 filter for transmitting.
>
> By way of explanation I have been using the waterfall display on DM 780 to
> set my filters as it seemed to accomplish what I needed. I have been
> following the K3 PWR Out discussion concerning PSK. I used a watt meter to
> determine that when transmitting PSK my power out is best over a 1000 Hz
> range centered on 1400 Hz in the passband of the 2.2 filter (using the
> waterfall to measure this). That is the reason I was trying to get
> everything centered on 1400 Hz in the passband of the transmitting filter.
> It is my understanding that any SSB transmission will go through the KSB2
> 2.2 filter? so it would be ideal to be centered on it?
>
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.0.233 / Virus Database: 270.10.16/1930 - Release Date: 01/31/09 20:03:00
>
>