Those were actually two different thoughts.
When I inject a signal with my KX1 at 7.040, I get an
image at 7.072 which is just about as strong. When I
go to the DSP image rejection sliders, they have no
effect on the 7.072 signal.
I also see images of QSOs on the other side of the
center frequency and can't reduce them.
I mentioned, hope against hope, that fixing the image
rejection problem might have some effect on the
artifacts you mentioned which I realize are something
inherent in the design and can't be eliminated.
Thanks for the note, Bruce. I'm going to stick this
thing on a scope later tonight with just power and an
antenna and see what I can see. I don't have a
computer in the shop or hamshack, both upstairs, so it
is a little inconvenient working on the radio since
the only computer I can use is in the dining room
which is downstairs. Keeps me fit, though.
Eric
KE6US
www.ke6us.com
--- Bruce Beford <bruce.beford@...> wrote:
Eric- I think you may be confused regarding image
rejection. What is
meant is when you inject a signal at say, 7.042,
which is about
14Khz BELOW the center freq of 7.056- The image that
you are trying
to null will appear at about 7.060, or about 14Khz
ABOVE the center
freq. The nulling process will not have any effect
on the junk
around 7.056. My understanding is that the stuff you
see there are
artifacts created by very low frequency noise within
the the sound
card, as well as other factors relating to this
low-cost design. A
high-end sound card may reduce this, but I would
like to hear from
others using the SR40 with something like the
M-Audio delta 44, or
other high-end cards. Hope this explaination helps.
73, Bruce N1RX
--- In softrock40@..., "Eric"
<eric_ke6us@y...> wrote:
The radio went together fairly easily, though I'm
at
a loss to figure out why an experimenter's radio
is
jammed onto such a small board. This might be OK
for
a production rig, but some room would be nice to
experiment.
That said, the radio works except there is no
image
rejection and the DSP image rejection controls do
nothing. The instructions say, "If the image
cannot
be nulled at least 50 db, then a problem
exists..."
Well, some guidance would have been helpful.
Especially, given my opening criticism.
I am reluctant to tear into this think quite yet
as
there is not a lot of room to work. I originally
thought it may be a transformer mis-wiring on my
part.
Again, we're talking an experimenter's radio on 40
meters where things are relatively less critical
than
other bands, so a little larger toroid with more
room
to make changes would make it a lot easier.
I'm hoping when I fix the image problem that all
that 7.056 +/- 5 khz energy is going to at least
be
diminished. 7.056 is S5. 7.051/7.061 are S3.
Anyway, I have no doubt the problem is my error. I
just want a little direction so that I can
minimize
stress on the board.
Eric
KE6US
www.ke6us.com
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