[ARC5] [MRCA] AN/PRC-74 Schematics

[WA5CAB at cs.com]

Gordon,

Yes, there are two ways to do it.  First, buy or rent (includs paying a 
commercial outfit with the capability) a scanner large enough for the job.  I 
usually do this for originals that are both taller than 11" and wider than 
17" unless the original happens to be a drawing with multiple smaller drawings 
whose exact position on the finished scan is not important.  Most 
commercial outfits have scanners where the scanning head is fixed and the paper is 
fed past the scanning head.  They have a hard limit in one dimension (usually 
height) but in the other are only limited by storage space and file size 
handling limits.  Back in the 80's before we got away from hard-copy inspection 
logs, my company used to routinely copy 8" x 200' logs on such machines.

Or second, starting with the largest scanner you can reasonably afford 
(typically 11 x 17), scan the original two or more times making certain that you 
have overlap between the scans.  

One of my pet peaves is that people who insist on scanning the fairly 
typical 11 x 24 to 11 x 44 found in many military TM's with an 8-1/2 x 11 bed 
scanner almost invariably miss the overlap.  Most scanner software defaults to 
cropping the edges.  Which means that if you scan an 11 x 17 original in two 
8-1/2 x 11 passes without offsetting the original toward the center you are 
going to miss from 1/4" to 1/2" up the center of the drawing.  

Also, examine the original and pick the best match line(s).  For example, 
never if you can possibly avoid it try to match up on a line that runs 
through the middle of a bunch of rotary switches, tubes, coils, etc.  Find match 
lines with the minimum number of lines on the drawing that cross the selected 
match line.  Then make sure that the match line areas are comfortably on 
each adjacent scan.  This could mean making more than the theoretical minimum 
number of scans of a drawing.  But scanning time is usually a minor part of 
total processing time.  And the fewer match points you have to get to 
register during the paste operation the quick an accurate paste can be achieved.  
If the match line has only horizontal lines crossing it and if the lines 
continue straight for at least a quarter of an inch on both sides of the match 
line, you don't have to worry greatly whether the horizontal match (left to 
right) is particularly accurate.  So long as the vertical match is correct 
within one or two pixels, no one later will ever know the difference.

Next, because paper is flexible and it is difficult to guarantee that 
horizontal and vertical lines on the original are horizontal and vertical on all 
the scans, straighten (rotate as required) the images on each of the 
individual scans, picking if possible a straight line that runs across both scans 
that are about to be pieced back together.  For example, many drawings will 
have a ground buss running much of the way across the middle of the original.

Then  one at a time, copy and past the small scans onto a blank full size 
page, lining up the edge or edges of the scan being pasted with the image 
already present.  This isn't too difficult when the original is say 11 x 30 and 
the scanner is 11 x 17 or even 8-1/2 x 11.  It gets much more complicated 
if both dimensions of the original are larger than either dimension of the 
scanner.  Depending upon the drawing, you usually end up having to match up 
two orthoginal match lines.  If for some reason not all of the horizontal 
lines are a perfect match and you get a little zigzag on some, delete the line a 
little ways to left and right and reconnect with a new straight line.  One 
cause of this problem is that the long supposedly straight line that you 
picked to use as a straightening reference may not have actually been straight 
because the original paper had differential shrinkage or because the line 
never was actually straight from the printer back when.

Further comments - 

NEVER use JPG for drawings or text!!!

NEVER scan black and white originals in color.  No one cares what shade of 
yellow the original has turned.  This can maybe be fixed later but it adds a 
lot of post-processing time and the end results are likely to be poorer 
than they could have been if the thing had been scanned intelligently to begin 
with.

Never scan text and/or drawings as anything but black and white 
(monochrome).  If the original is mixed text/drawings and B&W photos, make two scanning 
passes, one optimized for text and one for photos.  Copy and paste the 
photos onto the text scan.

Normally, scan at whatever the maximum resolution of the scanner and 
associated software is.  You can alway reduce the dpi later if you need to reduce 
the file size.

Never pull your brand new whiz bang scanner out of the box, plug it in, and 
start feeding manuals through it.  From the (poor) quality of 99-44/100% of 
the stuff available free (and a lot that isn't free) on the Internet, the 
scanners default settings are going to produce terrible results.  Most decent 
scanners (and/or their associated software) will have the capability to 
crop edges, reduce background clutter (grass cutting), adjust contrast and 
intensity (brightness), set to color, 256 or 16 grayscale, and monochrome or B&
W.  But you can bet that none of the default settings are going to be 
optimized for producing decent TM scans.

Scan to the file format best for cleaning up and straightening the 
drawings, generally single or multipage TIFF.  Do all post processing (like deleting 
coffee stains, mildew marks, solder burns, Scotch tape, fold lines, etc) as 
TIFF, where it's possible to do.  Straighten crooked pages.  Later, convert 
to PDF if you plan to distribute the completed file either for free or for 
pay.  If you distribute it for pay, don't expect to do that for more than a 
few weeks max.


In a message dated 11/30/2012 06:37:22 AM Central Standard Time, 
gewhite at crosslink.net writes: 
> Is there a procedure to scan oversize pages?
>   - Gordon White

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480