Off Topic but with so much expertise flying around I thought I would ask how
mechanical filters compare with crystal filters.
I think they were fairly low in frequency (455kHz?), so, not suitable in the
present discussion, but it would be good for our education at least.
David
G3UNA
John,
Please describe the quadrature phasing part of your receiver.
On weak signals, I often find narrower filter settings of the K2
make the signal harder to copy.
Part of that might be my bad hearing and the higher pitch
sidetone I like...
The noise and the signal seem to blend into one
Hi Brett.
John,
Please describe the quadrature phasing part of your receiver.
In general terms, the design is very similar to quadrature phasing receivers
used for SSB operation, except that since the bandwidth in this case is very
narrow, the 90 degree audio phase shifting network becomes
Its my understanding that they are not great other than
they do have steep skirts.
The R390 used IF transformers (tuned circuits) while
the R390A had mechanical filters.
The R390 was judged to work better, and the R390A was actually
designed to reduce cost through the use of the mechanical
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