[Milsurplus] RADAR Simulator Question

[J. Forster]

First of all, I'd like to thank everybody who responded, both on and off
list. The consensus seems to be that 5 or 6 bits will realistically
simulate real video signals, which is what I was after. I also appreciate
the comments about the varying intensity of the returns for realism.

Here is what we are trying to do:

The Battleship Massachusetts has several search radars with both A scopes
and PPI displays. In addition there is a Dead Reckoning system that
computes Latitude and Longditude, based on forward speed through the water
as measured by a Pitometer Log and gyrocompass heading. The DR system also
plots the ships position on a big chart table.

The ultimate objective is to have a PC execute preplanned courses and
speeds (as might have been ordered by the Captain), the DR system display
that information, and the RADAR displays show realistic PPI and A scope
displays of other ships and coastlines, much as might have been seen in
reality.

This sounds complex, but it is actually a collection of fairly simple tasks.

The Dead Reckoning system requires DISTANCE and SHIP'S OWN COURSE inputs.
These are synchro signals and can readily be produced by the PC interfaced
to stepper motors to drive two synchros, one for each variable. (That is
why I was searchinbg for synchro data a while ago). Given those signals,
everything else in the DR system will use original electro-mechanical
computers from 1942. BTW, they are absolutely beautiful... real marvels of
engineering. They do integrations, differentiation, and trig.

The RADARs are a bit more complicated. At the moment, we are not trying to
actually radiate for several reasons, including the FCC authorizations,
missing waveguides, and possible interferenc problems. Oh, and the antenna
drives need considerable work, atop the masts.

So the plan is to simulate the antenna AZIMUTH with a computer driven
synchro and stepper as in the DR system. The VIDEO simulator will be based
on a RAM or ROM which contains the VIDEO signal amplitude as data. The
addresses will be a combination of antenna AZIMUTH and time after the
TRIGGER pulse. The TRIGGER pulse will come from a free-running oscillator,
at the design PRF of the RADAR, and will start a counter for RANGE. The
RANGE counter output and AZIMUTH (digital) signals will go to the memory
to select the appropriate VIDEO data for that RANGE-AZIMUTH cell.  A PROM
would give a static display, a RAM could easily simulate an actual
operation. The reason for off-loading the RADAR video generation to a
separate box is to greatly simplify the SW timing issues. The RADAR
simulation needs to run in real time. The slave displays in other
compartments will get VIDEO, TRIGGER, and AZIMUTH signals as they would
have in WW II.

The possibility of using a flying spot scanner to input coastlines, etc.,
is interesting. In fact, there is a web site by a Dutch (?) techno-artist
who made a solid brass Enigma machine, that has a working cold war bomber
RADAR where scene simulation is done with such a scanner based on a
Tektronix monitor.

Thanks again,
-John

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