[EMAIL PROTECTED] wrote:
I read, with interest, the discussion about the K3's inability to
+ copy (or perhaps a better way to say it is to reproduce the audio of)
+ shortwave broadcast stations well without a wide FM filter. I just
The problem isn't for shortwave broadcast stations in general, most of
which are already restricted to the AM filter bandwidth, but for certain
ones, particularly intra-USA ones, that use more than one 5kHz channel.
+ wondered if there is not, or could not be made, a provision to have no
+ roofing filter for someone who wants to listen to shortwave. I haven't
This has already been covered, more than once. Without the filter, one
will get image responses at 30kHz less twice the DSP IF filter
bandwidth. You will also, probably, get aliasing at other frequencies.
You may also get desensitisation and IMD, as the result of signals
that not actually aliased into the DSP filer bandwidth.
The LC filter, that others have proposed, may be enough to constrain to
reject BC to BC interference, unless you are listening to something well
out of area, but no filter at all is a non-starter.
I believe there is a certain amount of LC filtering built in, but that
will not be designed to provide adequate image rejecting and elimination
of other close in aliases.
--
David Woolley
"The Elecraft list is a forum for the discussion of topics related to
Elecraft products and more general topics related ham radio"
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