KSB2 OP1 filter USB response...

[Steve Kallal]

It has been a few weeks since I built the KSB2 option. There is one problem
I haven't yet resolved. The response on the USB side of OP1 is not as broad
as the LSB side, and has a narrower peak. I didn't pay much attention to
this before. I've never transmitted in USB except for the digital modes
using RTTY reverse. I'm not much of a SSB guy.

These observations were made with the Spectrogram software. The symptoms are
quite noticeable by listening also.

73,

Steve N6VL
K2 #2289

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[Don Wilhelm-4]

Steve,

Tell us more.  The SSB OP1 filter as observed with Spectrogram in LSB or
USB should show a relatively flat passband extending from about 300 Hz
to 2600 Hz.  I do not understand 'peak' in that context.  It may be that
your BFO frequencies are not adjusted properly, but your use of the
'peak' term causes some doubt about what you are observing.  Can you be
more specific and descriptive?

73,
Don W3FPR

Steve Kallal wrote:

> It has been a few weeks since I built the KSB2 option. There is one problem
> I haven't yet resolved. The response on the USB side of OP1 is not as broad
> as the LSB side, and has a narrower peak. I didn't pay much attention to
> this before. I've never transmitted in USB except for the digital modes
> using RTTY reverse. I'm not much of a SSB guy.
>
> These observations were made with the Spectrogram software. The symptoms are
> quite noticeable by listening also.
>
> 73,
>
> Steve N6VL
> K2 #2289
>
>  

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[John Magliacane]

--- Steve Kallal <[hidden email]> wrote:

> It has been a few weeks since I built the KSB2 option. There is one problem
> I haven't yet resolved. The response on the USB side of OP1 is not as broad
> as the LSB side, and has a narrower peak.

Hi Steve.

Assuming your KSB2 is working properly, what you are seeing may very well be a
familiar characteristic of the crystal ladder filter used in the rig.

I ran some sweeps of my K2/100 several years ago, the results of which clearly
illustrate this effect.  Response vs. frequency plots may be found here:

      http://www.qsl.net/kd2bd/ksb2.html

The response is slightly asymmetric, with the roll-off being noticeably sharper
on one side of the passband than the other.

This is normal.

The side with the sharper roll-off will (in my opinion) "ring" more than the
gentler side.  As such, audio products that hit the "sharper edge" may appear
to be over-emphasized, so it might be beneficial to tailor your microphone's
audio response and the BFO frequencies to avoid hitting this edge with too much
audio.

Also, be aware that due to the mixing scheme of the transceiver, the audio
characteristics you observed are not only a product of the sideband selected,
but also the frequency band you've on as well.


73, de John, KD2BD


Visit John on the Web at:

        http://kd2bd.ham.org/
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.
.
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