Brent and group,
I can verify that the CASPPER system does perform this feat incredibly well
in most cases IF you have the right conditions. I've had two demos of their
product, one at our company in Santa Monica and another at an OATS. We
devised quite a few scenarios to test its capabilities. For instance, at the
OATS, we found a strong ambient. Then we took a signal generator (acting as
EUT) and moved it slightly off of the center frequency of the ambient in
order to measure its magnitude. We moved the EUT signal back to the exact
center frequency of the ambient and the CASPPER system was able to remove
the ambient and take a reading of the EUT signal to within 0.5dB of our
reading. We then proceeded to AM and FM modulate the EUT signal and still
the CASPPER system did a great job of reading it.
However, if the system does not get the differential it needs between the
ambient sensing antenna and the EUT antenna, the results are underwhelming.
At the OATS (nestled in a valley) the system had problems with multipaths.
At our company in Santa Monica, the system had problems with multipaths from
high rise buildings and the overwhelming magnitude of some ambients.
I packed these two demonstrations with as many engineers and technicians as
I could in order to get a broad range of skepticism and opinion. Our
engineers who have DSP and communications systems experience have no qualms
about the theory and spoke directly with the CASPPER engineer to quiz him on
what they were doing with regard to coherence. We all were satisfied that
the system can do what it theoretically claims. However, it's a bit finicky
and the ambient antenna placement (or multiple antenna placements) seems to
be critical. At this point, I disagree with the marketing of the product
that it is a virtual chamber in that it in no way removes the headaches of
dealing with the multitude of ambients the way that a physical chamber
would. It may even be that the users of the system become hyper-aware of
ambients as they use the system.
I've asked CASPPER to give me the names and phone numbers of customers who
own the system to see how it's performing for them in the real world and
gauge their customer satisfaction, but have not gotten this information yet.
I'm still a little disappointed that I haven't heard any responses from this
list server to my specific questions on this topic (see my 3/21/00 post).
For those of you who have witnessed their demos:
1. Did the system perform to your satisfaction?
2. Were you convinced enough to purchase it?
3. Was it worth the asking price?
Mike Murphy
Compliance Engineer
Alesis Studio Electronics
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