Good Morning Group,
I have sent the following to a number of hams having the same
problem mentioned by serveral in the group. Every SoftRock I have
built (30+ and lost count) has worked properly, some with extra
effort.
73,
Tony KB9YIG
Not being able to null the image has usually been associated with
the I and
Q signals being crossed or one missing. Check to make sure the
stereo cable
is connected to the board with the stereo connector tip to C18, the
via
nearest the corner board mounting hole. Check with a meter to make
sure
there is nothing to short one of the I or Q signals to ground.
Also, if the QSD circuit
is not getting one of the clock phases, open at a IC pin or short
between
pins, it can result an unbalance between the I and Q signals such
that one can not get a null. Solder bridges between IC pins can
be hard to see without looking with good lighting and magnification.
The voltage gain from RF in to I or Q audio outputs is on the order
of 40-45 v/v.
--- In softrock40@..., John <digi9345@y...> wrote:
Eric,
It sounds as though you and I are in the same predicament.
The SR40 is working pretty good but the image rejection controls
have no affect. Be sure to let us know if you come up with a fix.
John [K7SVV]
EricJ <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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John
K7SVV
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