KX1: Can I Improve Opposite Sideband Rejection?

[Kurt Pawlikowski]

Hi,

     Just a quick question: Can the opposite sideband rejection of the
KX1 be improved? The receiver is sensitive enough, but, when I have a
strong signal, as I tune by it, I can hear the signal on both sides of
the BFO. Granted, the opposing sideband is much lower, but still there.
Any thoughts? Thanks!

     Regards,

     kurtt

     Kurt Pawlikowski, aka WB9FMC
     The Pinrod Corporation
     [hidden email]
     [phone]
     http://pinrod.com
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[wayne burdick]

Hi Kurtt,

We used a 3-crystal filter in the KX1 so its passband could be varactor-diode tuned from CW to SSB bandwidths with an acceptable amount of passband ripple. While it would be possible to use 4 crystals, shoehorning them in would be tricky, and a more complex varactor-tuning circuit would be required.

73,
Wayne
N6KR


On Sep 15, 2013, at 7:08 PM, Kurt Pawlikowski <[hidden email]> wrote:

> Hi,
>
>    Just a quick question: Can the opposite sideband rejection of the KX1 be improved? The receiver is sensitive enough, but, when I have a strong signal, as I tune by it, I can hear the signal on both sides of the BFO. Granted, the opposing sideband is much lower, but still there. Any thoughts? Thanks!



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[Mike Morrow-3]

> Can the opposite sideband rejection of the KX1 be improved? The
> receiver is sensitive enough, but, when I have a strong signal,
> as I tune by it, I can hear the signal on both sides of the BFO.

That's characteristic of the KX1, which uses a 3-pole crystal filter
network in its IF.

The K1 has much better opposite sideband rejection because it has a
four-pole crystal filter network.

I supposed one could re-design the KX1 to add an extra IF crystal.
I wish that had been part of the original design.  I think it's
an important performance attribute, even on small QRP rigs.  It costs
so very little in terms of space, PCB real estate, and cost of parts.
It does make a noticeable difference.

Mike / KK5F
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