How to retrieve a corrupt signal ?
By XavSnap.
ZX81 'P' File Example.
Hi,
I will try to retrieve a bad Zx81 tape using on board wav tools.
The signal can't be retrieve using
the « Eighty-One » decoder. It use a level
tone decoder how count all higher pics throw by the trigger
level.
In the example, the signal isn't symmetric and.deaf
In
the « tool s» menu, select the
« auto-correct Symmetry » to retrieve all
upper pics.
Click on “Select All” , to work on the global length.
Now, open « Adjust the signal » menu,
There's
2 lines : End L (evel) en Start L (evel).
Both are used with the “Expend
selected wavs” button, to enhanced signal amplitude (Start
level to End level)
Just click the right or left mouse button
to set them.
Don't expend harmonics above the maximum level. (2/3 of the height)
Now, you be able to Expend the upper
pics to the same level !
The green Zone is used to select all
pics placed between the upper and the lower zone line.
(Use the
scroll bar to set them)
Now, Set to End L'evel using the left
click on harmonics picture.(click and move)
All pics will be
moved to the selected End L'evel
On
the right hand, there's a Beep counter.
It able to check if
there's some illegals harmonics.
Click on “24”
(“Reset Validation time” to select it on the
picture.
IIII<---1--->IIIIIIIII<---1--->
Where
(1) is the signal pause used to validate the signal (“ I
”)
Just select the trigger level (green zone) using the
left scroll bar.
Click on “Check ALL” or “Check
Selected”
In fact, this tool is optional,
the inboard Zx81 decoder set a “1” bit if there's more
than 5 beeps.
But, it will needed on the EO decoder.
Select Header and footer using right
click on the harmonics picture.
And click « set to
silence »
Note: (On the main
frame)
You can “Draw” the waves form using the
Shifted Left mouse click.
It
allow to remove a pic, or redraw it.
Click on the harmonic picture (Left
click) to set the Azimuth (level trigger on Zx81)
1/3 of the
upper height.
“Select All”, “Convert selection” and “Zx81 Bloc”.
Select
the Zx81 bloc, and click on the right button.
Select « Save
block as is... » to save the « P »
file.
If the waves forms are too deaf, you can convert
binaries using the “Zx81 blocks [PAUSE]” function.
The
software will get a significative signal (set by Azimuth level),
like the beeper rebound signal.
But this method is Hazardous.
Have Fun !
XavSnap.