Ferrum - I bring to your attention the “reflections on the steering wheel” of comrade Nemo.

                                
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           . - -Ferrum - - .    
          (С) Nemo,FOX RePrint  
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...   Предлогаю  вашему  внимaню
"размышления o рульном" товарища
Nemo, представлять которого сами
понимаете  , труд неблагодарный.
Текст   нагло   перепечатан   из
журнала "Радиолюбитель" and in effect
its orpomhoctu is divided into 2
parts...                        
                                
                                
                                
     Where did the border come from?     
                                
                  (C) Nemo      
                                
1 Introduction.                     
                                
  Lately, more and more often
have to deal with
frankly ignorant
ideas about the concept
Spectrum-architectures.           
IBM PC usersplaying
various imitators
Spectrum'a,consider themselves
advanced enough to
do different
statements that are impossible
regard it differently than
absurd. On this it would be possible
don't pay attention if
this audience held their own
prejudices and superstitions to yourself
and did not replicate them on
mass pagestechnical
publications     Not to be
I will give unfounded examples:    
                                
"...the presence of a stupid border
(who and why came up with it like this
big?) I noticed right away..."  
  And also there: "...in two
I repeated in the last chapters
CAPITAL truths. "             
                                
  Looks like it's time to get busy
in words.                      
                                
2.Technical standard.                  
                                
  Consider an existing
television standard and
let's try to establish a relationship
between its positions and
architectural and conceptual     
solution of the Spectrum-machine.       
  Number of linesZ=62S, number of frames
per second n=2S, which ishalf-frames2n=S0, and in each
even half-frame 313 lines, and in
each odd - 312 lines. B
Spectrum'e not used
interlaced, so
it can be assumed that
Z(st)=62S/2=312,S, a n(st)=2n=S0
Here and below under the designation
(st) will be implied
parameters, quantities and
values accepted in
TV standard;       aunder
designation                    
(sp)-corresponding values in
architectureSpectrum'a.  Moreover
designation (sp,A,B...)
implies sequence
narrowing (cut).   However, in
Spectrum value is used
Z(sp)=312, and it turns out
next number of frames
per secondn(sp):                
                                
                                
               312.S            
     n(sp) = --------- * S0     
                312             
                                
               z(st)            
      n(sp)= --------  * n(st)  
               z(sp)            
                                
        n(sp) = S0.080128       
                                
                             (1)
                                
  Для        любителей,програмно
реализующих         часы,(отсчетbpemehub programs) you can
recommend not counting everyone
62S frame pulse (as
usually this is done upon entry
maskable interrupt: signal
processor/bus *INT/.
The error is /n(sp) of the order
sixth significant digit possible
neglect, because she's on one or two
order of magnitude less error
quartz resonator           
                                
                                
           0.000128             
 /n(sp)= -------- = 2.S6*10^-6
 S0                
                                
                             (2)                                
There were exceptions.
For example, in Spectrum-clone of the brand
'NEXT' (discontinued in
second half90х) due to
introduction of the second
specialized kernel
(CPU+ROM), shaper function 
calibrated, precisely
corresponding to the TV standard
,video signal parameters),
the number of lines was exactly
Z(st) = Z(sp) = 312.S what on
the author's view, led to
unreasonable complexity.        
                                
  Another exception is
a well-known clone of Pentagon.
It implements 320 lines in
frame, because of what:               
                                
 312.S             
n(sp.pntg)= --------- * S0-48,83
 320              
                             (3)
                                
i.e.  inPentagon'e duration
there are more frames, but the number of frames itself
per second less than standard
values.  This is the reason
a widely known prejudice o
supposedly faster performance
Pentagon'a.     If we count
performance in absolute
units, namely, in the system SI,
(and not in arbitrary ones taken from
ceiling"parrots"), no
there are no misunderstandings.
For the sake of accuracy it is necessary
note that performance
(performancePentagon'a
really a little (at
percentages) higher than other clones and
equal to the performance of KAU-1024 v
normal mode. Misunderstandings
occur, for example, when
attempts to connect PAL and SECAM
encoders that "for some reason"
refuse to work.
The reason is non-compliance with the standard. 
                                
2.Frame format (width ratio
frame to height)                 
                                
     k(st) = 4/3 = 1.33         
                                
                             (4)
                                
  The Spectrum screen is used
resolution 2S6 points by
horizontal and 192 points along
twirled.  That is  matrix dimensions
display 2S6 X 192 pixels.
Comparing the sizes we get the same
most meaning:                 
                                
       2S6 4                  
k(sp)= --- = -- = 133(3) = k(st)
 192 3                  
 (S)
                                
3.Now let's digress a little and
Let's discuss the concept of a pixel -
minimum element
images.    Its main
cbouctbamu is equality
height and width.  Otherwise
in case one would have to enter
scaling operation.  A o
rotations in the screen plane
I would have to forget about it altogether
due to extreme complexity
cumbersome and ineffective
software support.  How to
volume of code, its complexity
creation and execution time.
As already stated in Spectrum
interlaced scanning is not
used, so the size
vertical pixelshp(sp)
is equal to one line:             
                                
                                
 h(sp)=312           
                                
                1 1       
     hp(sp)= ------- = ----     
              z(sp)    312      
                                
                             (6)
                                
Учитывая что k(st)=4/3, получаем
теоретически  необходимое  число
пикселей в строке t(sp):        
                                
 t(sp)=z(sp)*k(st)=312*(4/3)=416
                                
                             (7)
                                
  In practice, however, these
the ratio is definitely not
are observed, and technical
time intervals required
to form a reverse stroke
frame and line scans are not
strictly proportional between
themselves and may vary according to
within certain limits for
various TVs
classes, brands, manufacturers.
This is indirectly indicated in
TV standard in the subsection
"line resolution",
no less, from 2S0...300 to
S00...SSO, depending on
TV receiver class. Therefore in
Spectrum, foravoidance
geometric distortion type
OVAL (click the arrow - you will see)
additional ones are introduced, as if
imaginary pixels (they are not
are displayed on the screen because
fit into technical
line scan intervals)
quantity t(sp), equal to 32
"imaginary" pixels.              
                                
t(sp) = t(sp)+/t(sp)=416+32=448
                                
                             (8)
                                
4.     Number of reproduced
gradations of brightnessy(st)=10.  B
Spectrum four are used
binary signal: one luminance
and three colors.                 
  Having considered the calorimetric
machine color chart can be
notice what she has
uniform spot coverage,
consisting of 12 colors
signals, two white signals
colors of different brightness and two
matching black signals.
There is an opinion that Spectrum
does not fully use the resource
in terms of brightness/color only correct
from part.   Let's look again
standard (4) nonlinear
distortion,%, no more than:          
                                
a) signal in the brightness channel +-10
b) in the channelchromaticity+-10
                                
Since channels 3 (R,G,Beither
R-Y,B-Y,Y), then distortion
needs to be summarized as
linearly independent quantities: 
            ____________________
 / ___ ____  
/(R,G,B)=/ 1/2  = 0.7/0,03= 
        /      /__             
                RGB             
                                
           = 12.1-(+-12,1%)     
                                
                             (9)
                                
  Учитывая,что  искажения  могут
совпадать  по  знаку,  для любой
пары     каналов,    и    считая
ограничением  ресурса совпадение
соседних  комбинаций  яркости  /
цветности,получим   S  различных
уровней по каждому из каналов.  
 Итого имеем:                   
                         h(sp)  
            Y(sp)   a(sp)  -1   
КПД (sp,Y)=------ = ----------- 
            Y(st)    a(st)      
                                
                            (10)
                                
где     Y(sp),Y(st)-ресурс    по
яркости  /  цветности Spectrum иTV receiver, respectively;  
                                
a(sp),a(st)  - number of transmitted
levels on one channel.       
b(sp),b(st)  - number of channels.    
                                
Having imagined, we have (1-in the numerator
means black color
is specified in SPectrum two
combinations).                  
                                
              4                 
             2 - 1 1S     
  Efficiency(sp,Y)= ------- = -----3               
               S 12S    
                                
                            (11)
 It should be noted that this is very
rough estimate from below.   When
trying to get more accurate
estimates are growing very quickly
unclear in the statement of the problem.
Miracles don't really happen.
It is impossible to push 3 signals
, equivalent to brightness in
black and white receiver, striped
6,S MHz, with a constant ratio
signal/noise Therefore manufacturers
TV receivers are being shoved
existing channel capacity deficit
into additional distortions and
restrictions.           For example,
aperture, or reduced by
horizontal and (or) vertical.
This is not noticeable to the eye, due to
its physiological cbouctb,
for example small parts
the eye perceives images
as unpainted, regardless of
their colors.  However, from what has been said
it does not follow that in Spectrum it is necessary
to improve something. The payback will be
sharp decrease in densitycode.
As an example you can
bring users
computer "Vector", which
flattered by technical
characteristics (full-length
graphic screen) and not
waited, by and large
images on it. Image
cannot appear without software, a
Software in turn cannot
appear due to their
high cost, because    process
creating giant (
compared to Spectrum)
programs are too labor intensive. Well
a lack of processor power and
memory capacity is
easily overcome technical
obstacles, i.e.  just
circumstances of the scene,
not changing the effective cause
essentially.  The reason, by and large
account, again the same - non-compliance
standard   Generally speaking,
system, including
technical, being optimal in
in general, should contain
suboptimal nodes. For complex
technical product much
the integrity of the structure is more important,
- harmony of the product as a whole,
because      the user will
evaluate it based on practical
applications, noton technical
characteristics.                
                                
                                
                                
 Let's summarize.  Four of  
the above points is
akcuomatuka Spectrum'a, or ,
as it is now customary to express it in
popular publications, copybooks.
Further, no more than
the magic of numbers, consequences.
Based on these four
points, out of a hat
magician, pull out
different, long-familiar
constants.  For example, multiplying
frame rate per number
lines in the frame, we get:          
                                
f(st) = n(sp)*z(sp) = S0.08*312=
=1S62S [Hz];f(st) = f(sp)         
                                
                            (12)
                                
where f(st)-lowercase frequency
TV receiver scans.  Taking
reciprocal of frequency
line scan, we get
line durationtr(sp)      
                                
                  1             
 t (sp)=t (st)=-----=64[μs]u u f(st)           
                            (13)
The figure (3) shows the form
TV signal in line interval
blanking [6],a in the table [1]
corresponding parameters
Spectrum-clones.                
                                
        t (st)                 
         u 64 1        
Tr(sp)=--------=-----=--- [ISS] 
        t (sp) 448 7        
         u                      
                                
                            (14)
                                
где     T(sp)    -    абсолютная
длительность  (величина пиксела)
в единицах времени.             
                                
            1                   
F(sp)=0.S*------= 0.S*7=3.S МГц 
          Тр(sp)                
                                
                            (1S)
Where f(sp)-necessary and
sufficient bandwidth
yctpouctba display Spectrum.
The coefficient 0,S takes into account that
fact that in one period
one white and one
black element, i.e. one period
consists of two half-cycles. B
that it's literally
corresponds                   
TV standard, you can be sure
looking at Fig. 4 [4]
Shaded field areas
admission.     As you can see, the strip
black and white transmission
TV (Figure 4a) has a reserve
npumpho one and a half times.  B
this color television set
the resource is used by 100% This
explains the fact that when
working Spectrum in mode
character series (reading, typing
texts, programming)
usersprefer
use black and white
mode, and when displaying
video sequences (games, pictures)
color mode TV.  Improve
color TV parameters
for working with character series
you can by switching it to mode
PAL (increases resolution
horizontal ability),
turning off the color, or, as most
the best solution is to give up
connections via HF and use
joint SCART i.e. give signals
directly to
video amplifiers by channels R. G.
B.   It's better than smoking
TV, making homemade
connection.  If the block is SCART
no, it must be installed.
Any TV studio can do this and
corresponds to the profile of their work.
Thus, thanks to
standard junction, appears
developed infrastructure
yctpouctba display support
Spectrum, focused on
work with the population at affordable rates
prices for him.border             
                                
  Now, in fact, you can
go to the curb. To begin with
it is useful to quote excerpts
from the television standard [4].   For
visual appearance
distortion is shown schematically
in the corresponding figures. Not
one should think that everything
TVs have all these
defects in the amounts specified
below.                           
                                
  The given parameters are in total
they only state the fact that
if they (these parameters) are in
during operational
period will take the specified
values, but will not exceed them, as
separately and by
collectively, then TV
recognized as technically sound
and fit for use. So,
according to [4]:                   
                                
  1.   Nonlinear distortion by
horizontal and vertical - 7%    
  2.   Geometric distortion
type "barrel" (Figure 1b), "pillow"
(Figure 1d), parallelogram - 3,S% 
  3.    Background distortion from
non-synchronous network via TU,
geometric - 0.2%           
                                
  Dimensional instability
images:                    
                                
  4. From self-heating - 3%      
 S. From voltage changes
power supply from 198 to 231 B - 3%    
  6. From a change in the current of the rays in
within TU - 4%                
  7. Reverse stroke duration
from sweep period:           
  a) frames - S%                
  b) lines - 20%               
                                
  Last Distortion Amount
seems to be maximum and at
she needs to stop
especially.       Firstly, according to
TV standard, duration
horizontal damping pulseis 12 μs or 18,7S% from
scan period (Figure 3), i.e.
additionally allowed1.2S%
image loss by
horizontals, this is, in fact,
there is distortion itself.
Duration of personnel suppression
impulse is 1.S ms. When
half-frame durationJ(st):   
 1 1            
J(st) = ------ = --- = 20 [μs]
 n(st)     S0            
                                
                            (17)
Ошибка составит:                
                                
            1                   
/J(st) = ------ * 0.0S = 1[мкс]
           n(st)                
                                
                                
                            (18)
                                
Длительность  кадрового гасящего
импульса   1.S  мс,  что  больше
полученного   значения,  поэтому
ошибку  можно  считать  нулевой,
т.к.entire reverse stroke (with
tolerance) fits into the damping
personnel impulse.               
                                
  All these distortions in,
the overwhelming majority,
appears at the edges
images, i.e. on the curb. And
TV manufacturers usually
take them off the screen.
Considering all these distortions mutual
(pairwise) independent, you can
get the equivalent total
distortion (rough, approximate)
calculation):                       
                                
        __________________      
       / __7___               
      / 1  2            
   k=/ ----/ / =         
   / 2 /____ n            
           n=1                  
                                
       ________________________ 
      /    2     2     2    2   
= 0.7/ 0,07+0,03S+0.002+0.03  + 
   /                           
                                
-----------                     
     2    2                     
+0.03+0.04= 0.0683              
                                
                            (19)
                                
  For color TVs
the above distortions
it is necessary to add distortion for
counting the divergence of rays on the screen
kinescope (Figure 1d) and
discreteness due to the mask, i.e.
approximately total distortion
are 6.8% of the size
screen.  Here under the distortions
refers to the loss of elements
images adjacent to the edges
screen.     With this kind
distortions were often encountered
computer users
"Radio-86RK",("Mikrosha").       
                                
  This is usually expressed as
that the prompt (cursor) located
at the top left of the screen,
disappears behindscreen limits
(for example, when warming up
TV).                    
                                
  Of course you can spin it
horizontal dimensions and
verticals, fortunately the regulators are still
found on TV.  But
there are three large"but".          
                                
  First.  Since the adjustments
sizes are interdependent (through
parameter k(st), then twist
you'll have to do both.         
                                
  Second.   All those distortions
which manufacturer
I carefully hid the TV set
beyond the edges of the screen, crawling out.
For example, the beginning and end
reversal reversal
look like fat glowing ones
points. Sometimes - illuminated pieces
the same reverse sweeps.
And other beauty in the same spirit. 
 Third.   You have to twist
regularly, back and forth. Either
have to give up
using the TV
directpurpose.   View
specific distortions
in parallel with the TV show is unlikely
will it deliver aesthetic
pleasure.                    
                                
  The reason for this mouse fuss,
and also ahov, ohov ee
accompanying persons - non-compliance
standards in concept
"Radio-86rk".                   
                                
  However, let's return to the curb.
Considering all of the above,
it is possible to determine from which
technical efficiency
Spectrum uses screen
TV receiver.    Otkoppektupyem
theoretically possible
resolution, taking into account the nuances
practical implementation.    B
ideally resolution
points:                          
                                
N(sp)=Z(sp)*t(sp)=Z(sp)*k(st)*  
                                
        2                       
*z(sp)=Z(sp)*k(st)=312*416=     
                                
=129792                         
                                
                                
                            (20)
                                
или:                            
                                
N(sp)=312*416=129792            
                            (21)
                                
  Реально возможное разрешение в
строке   изображения   с  учетом
обратного хода (рис 3)          
                                
            64-12               
Z(sp,real)= ----- * Z(sp)*k(st)=
             64=338                            
                                
                            (22)
                                
С      дополнительным     учетом
k-искажений:                    
                                
z(sp,real,К)=z(sp,real)*(1-k)-31
                                
                            (23)
                                
Теперь    coothecem   полученное
разрешение       с      размером
Spectrum-матрицы по горизонтали:
(sp,N)                          
                                
               2S6        2S6   
КПД (sp,N)= ---------- = ----- =
           z(sp,real,К)   31S   
                                
= 81%                           
                            (24)
                                
Собственно,    такой   результат
подразумевался  с самого начала,
но  в  утверждении стандарта (см
п3)   "Разрешающая   способностьreceiver", this result
is contained in an implicit form.
Therefore, I had to clarify this
well copybooks.   moreover, for
TVs with screen diagonal
less than 30 cm TV resource
involved 100% i.e.
Spectrum architecture lies exactly
at the lower limit of the TV standard
by resolution. What
the same applies to kuheckonob with
with a diagonal of less than 30 cm, then they
widely used, for example
in technological equipment
how yctpouctba display
technological controllers.   
                                
  To understand a lot
is it or is it little, 81%, we will give
a few examples.     Efficiency
secondary sources
power supply with capacities
is about tens of watts
70...80% ANDthis is optimal
meaning.  At lower values
- poor dimensions and dimensions
indicators, with large ones - low
reliability. Optimal loading
industrial enterprise -
70...80%.  At lower values
- low profitability, with
big ones - rush rush, hassle,
hack work and defects, missed deadlines
supplies.                       
                                
 Conclusions.                        
                                
  Probably the question raised in
title of the article, clarified in
to a sufficient extent.  Someone's
from users Spectrum'a
doubts may arise, a
is it worth using at all?
TV.    The answer is absolutely
definite - worth it. No matter how much
the display was not good, nothing,
Moreover, the user
can see on the screen
TV in monitor mode
Spectrum, he's not there anyway
will see.  The cost of repairing the display
platforms IBM PC v
St. Petersburg is
order S0 USD (without price
delivery), i.e. about that much
how much does a new one cost?
black and white tv
production6elarysand.          
                                
  Domestic monitors
productions released in
late 80s, early 90s
should not be taken at all
calculation, since first of all they
have fully developed technical
resource and are characterized by low
reliability and non-compliance
alsoGOSTу;  secondly, everything
without exception, domestic
displays are essentially the same
TVs, but without
radio channel.                    
                                
  Who is not convinced by the considerations
stated in the article, we recommend
familiarize yourself with
this mode of operation of the TV,
like teletext.                  
                                
  Character row mode,
developed by ourselvesTV people, like two drops
waters are similar
Spectrum's mode. Essentially
this is independent confirmation
as the above is true,
and integrity and
organicity of the complex
(Spectrum + TV receiver)       
                                
 And finally, I would like
apologize for possible
inaccuracies and original
designations, unusual
TV people  The author expresses
thanks toS-Pb-sky
Television Institute,
employees of the department GONTI
(technical library, and
A.6.6ypkobckomy personally for
materials provided on
TV-theme.