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
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--- 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
