On Mar 5, 2005, at 3:27 AM, Stewart Baker wrote:
Anyone any experience of, or thoughts about adding another 3 crystals
to the K2
2nd crystal filter ?
Hi Stewart,
The present 2-crystal filter (as on newer units, or older units with
the 2nd XFIL mod) is very carefully designed to provide different
bandwidths on CW and SSB. Equally important, this filter must be
centered at the same frequency as the main filter over the full
controllable bandwidth range. L34 and related circuitry, along with the
varactor diode, accomplish these tasks.
If you wanted to add more crystals here for the purpose of improving
ultimate attenuation, two crystal filters switched by pin diodes would
be needed, along with a complete re-design of all associated circuitry
(I.F. amp output, product detector input, CW/SSB control, bandwidth
control in the CW case). This would be very difficult and
time-consuming, and the resulting circuit would not fit in the present
location. That would require the use of coax cables to a separate
module, along with other potential issues such as RF pickup. Chances
are the result would not be much of an improvement.
If your goal is to improve ultimate attenuation, the KDSP2 is a much
saner route.
73,
Wayne
N6KR
---
http://www.elecraft.com
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