External PAN with PMSDR question on filters

[PA3CW]

Hi all,
I recently completed a small SDR receiver called PM SDR.  I am using it with HDSDR software. Currently i have it connected to the IF out on my K3 to use it as panorama view.  In the software HDSDR i have to set some offset values in the different modes to have the PMSDR and K3 in sync.
That is going fine, however, when i switch my filters i.e. in CW from 400Hz to the standard 3,7 kHz the synchronisation is lost and i need completely different offset values.  Why is the offset changing if i change filters? Is there any way i can correct this in the settings of my K3?
Thanks
Dick PA3CW

[Bill W4ZV]

PA3CW wrote

Hi all,
I recently completed a small SDR receiver called PM SDR.  I am using it with HDSDR software. Currently i have it connected to the IF out on my K3 to use it as panorama view.  In the software HDSDR i have to set some offset values in the different modes to have the PMSDR and K3 in sync.
That is going fine, however, when i switch my filters i.e. in CW from 400Hz to the standard 3,7 kHz the synchronisation is lost and i need completely different offset values.  Why is the offset changing if i change filters? Is there any way i can correct this in the settings of my K3?
Thanks
Dick PA3CW

I'm sure you meant to say standard 2,7 kHz...not 3,7 kHz.  The reason for the difference is that 5-pole filters (e.g. 2.7 kHz) have a large offset compared to 8-pole filters (e.g. 400 Hz).  You can either install a 2.8 kHz 8-pole filter or compensate for the offset in your software.  Unfortunately it is not possible to correct for this in the K3 itself.

73,  Bill

[Bob Cunnings NW8L]

Actually, there is more to it than just the 5-pole filter offset.

The panadaptor offset between the carrier and the IF center can shift
as filter width increases because the K3 doesn't let the lower edge of
the filter fall below 200 Hz. In CW mode for example, using a pitch of
600 Hz, there is a change in the offset required when the filter width
exceeds the point where the IF center can be offset by the CW pitch
frequency (where (200 + width/2) > 600).

I noticed this when hacking PowerSDR/IF-Stage here to make some
improvements. The definition for command FI in the K3 Programmer's
Reference states:

FI * (I.F. Center Frequency; GET only)
RSP format: Finnnn; where nnnn represents the last 4 digits of the
K3’s present I.F. center frequency in Hz.
Example: If nnnn = 5000, the I.F. center frequency is 8215000 Hz.
Intended for use with panadapters, which need
to keep track of the exact I.F. center frequency as filter bandwidths
and shifts are changed by the operator.

If you don't account for all this the position of the filter passband
relative to the carrier frequency isn't displayed correctly on the
panadaptor.

Bob NW8L

PA3CW wrote:

>
> Hi all,
> I recently completed a small SDR receiver called PM SDR.  I am using it
> with HDSDR software. Currently i have it connected to the IF out on my K3
> to use it as panorama view.  In the software HDSDR i have to set some
> offset values in the different modes to have the PMSDR and K3 in sync.
> That is going fine, however, when i switch my filters i.e. in CW from
> 400Hz to the standard 3,7 kHz the synchronisation is lost and i need
> completely different offset values.  Why is the offset changing if i
> change filters? Is there any way i can correct this in the settings of my
> K3?
> Thanks
> Dick PA3CW
>

I'm sure you meant to say standard 2,7 kHz...not 3,7 kHz.  The reason for
the difference is that 5-pole filters (e.g. 2.7 kHz) have a large offset
compared to 8-pole filters (e.g. 400 Hz).  You can either install a 2.8 kHz
8-pole filter or compensate for the offset in your software.  Unfortunately
it is not possible to correct for this in the K3 itself.

73,  Bill
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[PA3CW]

Hi Bob,
PMSDR now works flawlessly with the K3 as panadapter!  I have been in contact with the designer (Martin, IW3AUT and he wrote a new .dll file specially for the K3, which reads out the IF frequency and adjusts the PMSDR to be completely in sync. Now changing filters or modes has no effect on the waterfall and other screens. Worthwile to consider a PMSDR now.  Apart from the use as panadapter i use it for receiving LF frequencies which i cannot do with my K3. Nice combi, especially using the HDSDR software (www.hdsdr.de).
Best 73's
Dick