[Milsurplus] Flying Spot Scanner... was RADAR Simulator Question

[Tom Dawson]

John,

The flying spot scanner is a fun idea, but I agree that digital would be 
better, particularly given that, in addition to the static nature of the 
Flying Spot there's the issue of converting the raster scan into the 
Bearing/Range/Amplitude format of the PPI.

RE: Data Format:

So it sounds like each bearing consists of 1024 amplitude samples and each 
amplitude sample is an integer of up to 8 bits (if you're storing it in 
EPROM or something like that, then you're probably stuck with 8 bits of 
storage, anyway).   Actually I would not care about the number of amplitude 
bits as I'd be truncating floating point numbers anyway.

What I would need to generate the Bearing/Range/Amplitude data would be 
(minimum) course and speed of own ship, course and speed of targets. 
Alternatively, lat/long/time for own ship and targets.  (Actually lat/long 
is better as I already have functions for calculating bearing, range, and 
aspect angle from lat/long).  Alternatively, starting lat/long and 
time/course and speed for each ship.

Also I would need the RF characteristics of the RADAR, Tx Power, Antenna 
Gain, Rx Bandwidth and Noise figure if you've got it but my guess is 20 dB 
is a good guess for noise figure.  MDS would suffice for RX sensitivity, if 
you have that number.

If you can point me to the ships you want to simulate, I can guestimate an 
RCS Max and Min if I can find a profile Then assume that it changes 
sinusoidally between max and min vs. aspect angle.  They all had vertical 
sides and lots of right angles so would have been good reflectors.  .

Not having infinite time to put into this, I would assume a flat earth for 
the lat/long calculations as all my previous work has been at relatively 
short ranges.

How long an engagement are you intending to simulate?  If you've got a long 
byte-wide Eprom, then, assuming you have 1024 bytes per angle, and 360 
angles per sweep, 368,640 addresses per sweep.  Given 10 sweeps per minute, 
that would be 3,686400 bytes per minute and 22,118,400 bytes for an 
hour-long engagement.  (this assumes that you have byte wide memory, and 
decode the lower 10 address bits as range and the next lower 9 bits as 
bearing etc.) That would be 21 8M X 8 Eproms , if that is the way you're 
doing it, which is not out of the realm of possibility. This  can be reduced 
of the beamwidth of the antenna is more than 1 degree.

Of, course, a PC reading a disk file, would not have that problem.

I might suggest that you generate the range sweep voltage with a DAC so that 
your range data and sweep are forced to synchronization, if you haven't done 
that already.

If you wanted coast line included I could probably use SRTM data for that, 
but I would want to do that later.

Just letting the imagination wander.....

Interesting project.  How long a sequence have you simulated before?


73

Tom
WB3AKD

----- Original Message ----- 
From: "J. Forster" <jfor at quik.com>
To: <W9RAN at oneradio.net>
Cc: <milsurplus at mailman.qth.net>; "n griggs" <n_griggs at bellsouth.net>
Sent: Saturday, October 10, 2009 1:15 AM
Subject: [Milsurplus] Flying Spot Scanner... was RADAR Simulator Question


> Until the late 60s or early 70s, there really was no other way, except a
> TV camera, to get images up on a TV. PROMs were tiny.
>
> -John
>
> ===============
>
>
>> n griggs wrote:
>>> I haven't seen one in AGES!!!
>>>
>> I hadn't either until two hamfests ago, when an early and very dirty
>> 1077 followed me home for $5.  After spending a couple hours cleaning it
>> up, at the next hamfest a guy had a like-new 1077B -  the latest model
>> -  with the original manual and all the slides that I just had to have
>> for only $20!
>>
>> I wanted one to use in restoring old TV sets but to my surprise, the
>> manual specifically explains how to use the flying spot scanner to
>> generate video displays for signs, advertizing,  "video paging"
>> announcements in public places, etc.   My guess is that it was the only
>> thing like it for the price at that time.
>>
>> 73, Bob W9RAN
>>
>>
>
>
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