Electronics

Guest

Thanks VERY much for all the informative posts. Please keep em' coming
if you have other info; I'm very grateful.

I'm old enough to remember the big multi-channel analog recorders, but
not quite old enough to have ever used one... :-) Will do more digging
on IRIG, Enertec, Ampex, etc..., as well as the Linux/RAID
configurations, and post what I find.

To answer some of the other questions:

Yes, recording analog close to the antenna gives me the easiest way to
replay a scenario, provided the tape stability and dynamic range are
sufficient. 8 antennas would only require recording 8 channels, but if
I have to record IF instead of RF, it's 24 channels, because we're
actually pulling 3 different signal bands out of each antenna.

Simulation is not feasible *yet*. I need real data from some really
busy airspace first (hundreds of planes, with their tcas and
transponder systems squittering away) in order to get realistic
statistics (signal levels, overlaps/collisions, etc...) Then I can
create all kinds of models with controlled deviations from a known,
realistic environment. But the "real world" sanity check is essential.
Analog recording is preferred, to capture the effects of ultra-close
transmitters saturating my receiver.

Aircraft will either be a slow jet or a small turboprop, depending on
which is available. No high-rate maneuvers. I don't know what to expect
in terms of microphonic effects from aircraft vibration, but as long as
it's realistic (on the antennas, not on my recorder!), I'll be glad to
have it. (Ideal scenario would be jet *and* turboprop data thru same
airspace at same time, to see any differences.)

Not yet sure how I would interface my A/D converters to a fast disk
array, but since I have an FPGA deserializing and processing the A/D
input, some compression inside the FPGA (simple deltas?) is an obvious
option that I didn't think of; thanks for pointing it out!!!

Regarding the 90GB/min disk arrays: I didn't know you could get 'em
that fast! (Any recommended suppliers?) 12 channels at 90MB/sec = 64.8
GB/minute; at that rate I could put about 16 minutes of uncompressed
data on a 1TB drive. That would certainly get me out of the starting
gate.

Thanks again, very, very much!

mj

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