I've been wondering about noise from the Arduino as well. I'm
working on a Kicad pcb layout and thought the Arduino pro mini
3.3V, 8MHz version would work best since it doesn't have a USB
connector which can be a source of noise. I plan on using sockets
for everything including the PE4302 attenuator module. The SAW
filters I just ordered from Germany so I don't know when they'll
arrive but I would like to make a module out of those too. I guess
there will need to be some shielding around the Si4432 modules and
Arduino and plenty of bypass capacitors on power lines. Since I've
never built a SA it's all experimental for me. As for the SAW
filters, the coupling between them is probably ok as the are in
series so whatever impedance they are will be matched. Eric seemed
to imply that the matching inductors and capacitors are not that
important in his build article. However, if you take the modular
construction approach, you and try out different variations to see
which works best.
Jerry Ponko
AC9NM
On 1/2/20 1:00 PM, Jerry Gaffke via
Groups.Io wrote:
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Niels,
That may work as is.
Or it may need a few iterations of the layout to work well at
these frequencies.
A few things I'd be scratching my head about:
How solid is the ground plane???
Can the receive path from SMA to Si4432 be optimized for a short
and straight path?
from one end to the other to minimize coupling between elements
(perhaps using coax for the LO from the second Si4432 to the
mixer)?
Should the longer high frequency traces be fatter to better
approach the 50 ohm system impedance?
Will noise from the Arduino overwhelm what you are trying to see?
Can the circuit elements be broken up to allow for shields to be
added?
Should there be a series inductor added between the two SAW
filters?
Jerry
