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G8MNY > TECH 29.05.19 10:02l 116 Lines 6234 Bytes #999 (0) @ WW
BID : 6582_GB7CIP
Read: GUEST
Subj: Sound Levels, dBA dBB & dBC
Path: IW8PGT<CX2SA<HP2BWJ<I0OJJ<GB7CIP
Sent: 190529/0858Z @:GB7CIP.#32.GBR.EURO #:6582 [Caterham Surrey GBR] $:6582_GB
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
\ Hz 20 50 100 200 500 1k 2k 5k 10k 20k
SPL\ ÚÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÁ¿
140dB ´`-.__ ./ Ã140dB
130dB ´_ ~``---...___ Threshold of Pain Baby's _./ Ã130dB
120dB ´ `--.. ~`````--------------..____ Cries? _..-'' .Ã120dB
110dB ´`-._ ``--...___ 120dBP ~`-....-' __ _./ Ã110dB
100dB ´-. `-._ ````--.._____..------....____ _..-'~ ' Ã100dB
90dB ´-.~`-._ ~`Ä-.._ 100dBP ~`--'~ _.._ ./Ã 90dB
80dB ´-.`-._ `-._ ~``---...._______..----.....___ _..-' `'~ Ã 80dB
70dB ´\ `-. `-._ `-..__ 80dBP `--' _.._ ./Ã 70dB
60dB ´ \ `-. `-._ ~``---..._______..----.....___ _..-' `-' Ã 60dB
50dB ´ \ `-._ ~`--..__ 60dBP `-' _.._ ./Ã 50dB
40dB ´ \ ~`-..__ ~`--._____.-----.....____ __.-' `-' Ã 40dB
30dB ´ ` ú. ~`--..__ 40dBP `'~ _.._ ./Ã 30dB
20dB ´ Threshold` - _ 20dBP~`---------.....____ __.-' _ `--' /Ã 20dB
10dB ´ Of Hearing ` - . _ `~ / \ _ / Ã 10dB
0dB ´ 0dBP ~ ` ` ' ' ' ' - . _ . . / Ã 0dB
ÀÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÂÙ
20 50 100 200 500 1k 2k 5k 10k 20k
Gain
0dB´ _ . , - - . , _ Ã 0dB
-10´ _.- ' ` -Ã -10 dBA is for sound levels up
-20´ _-' Ã -20 to 55dB, it has a response
-30´ _-' Weighting Curve A Ã -30 peaking at 2kHz with heavy
-40´ _-' Ã -40 LF cut of -50dB @ 20Hz &
-50´_-' Ã -50 -10dB @ 20kHz.
ÀÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÙ
20 50 100 200 500 1k 2k 5k 10k 20k
Gain
0dB´ _ . , - - - - - - . , _ Ã 0dB
-10´ _.- ' ` -Ã -10 dBB is for sound levels
-20´ _-' Ã -20 between 55dB & 85dB, it is
-30´_- Weighting Curve B Ã -30 flatter than dBA with only
-40´ Ã -40 -24dB @ 20Hz LF roll off &
-50´ Ã -50 the same -10dB @ 20kHz.
ÀÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÙ
20 50 100 200 500 1k 2k 5k 10k 20k
Gain
0dB´ _ . , - - - - - - - - - - . , _ Ã 0dB dBC Weighting is level above
-10´- ' ` -Ã -10 85dB, it is quite flat 30Hz
-20´ Ã -20 to 10kHz, & only -10dB roll
-30´ Weighting Curve C Ã -30 off @ 10Hz & 20kHz. It is a
-40´ Ã -40 frequency response with the
-50´ Ã -50 flattest weighting, almost
ÀÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÙ the same as an unweighted
20 50 100 200 500 1k 2k 5k 10k 20k Sound Pressure Level (SPL).
SB IBM @ WW
Laptop HDD Repair
By G8MNY (New Feb 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I have an old DEL black & white laptop ideal for /P packet work, as it has the
same 12V socket connections as the TNC & Rig. But over the last few years it
has been more & more difficult to boot up from cold. I say cold as if you leave
it to warmup, or apply a lot of heat (hair dryer) to the drive, you hear a
click & it works 100% with no errors at all.
As this is not a practical solution & compatible replacements are unavailable
(a memory stick & adaptor was my next port of call). Not to be out done &
having a background in real engineering (PRESTEL) on old exchangeable drives, I
decided to strip down the small HDD, to see what was wrong! Opening a sealed
drive not in a clean room, I thought would nearly always result in a damaged
head crashed drive, but I was wrong & have got away with it OK!
INSIDE THE HDD
Inside the drive you see - - - - - - - - - - - -
this sort to layout. / _-Ä~~Ä-_ Park |
/~ ~\ Magnet
The tiny heads are on the | / \ ÚÄ/ |
end of an pivoted arm which | H\ | ³*/ H=Heads
also has the head moving || \\ | ³³park | o=Arm Pivot
bare actuator coil inside ³ Axle() arm\ ³ ³³Arm
a powerful magnet. || \ \_³³ |
| \ o ===\\
Under the iron oxide | \ Platters / \_// \\|
covered recording platters \ / ||coil//
is the brushless platter \ ~Ä-.__.-Ä~ \\ // |
motor, axle & main bearing. - - - - - - - - - - - -
HEAD PARKING
As this is a laptop drive head parking (put heads on an inside track for
landing & have less vibration during transport) is important, & this is where
my trouble is.
A steel park arm limiting the head travel, normally sticks the park magnet at
power off. But when cold the actuator coil has not enough force to unstick
this, however when hot this is not quite so powerful, & you can hear a click as
the actuator frees the arm from the magnet. At the end of the arm is a tiny
sliver of something to give a magnetic residue gap to limit the magnet pull.
I now suspect this has worn down a few microns increasing the park magnets
holding power.
MY SOLUTION
This was really an old dodge for sticky relays etc, I applied a sliver of
sticky tape about 2x 3mm to the face the park magnet. This will undoubtedly
wear through in a few 1000 parks but it certainly works! Care was taken not to
"touch" or "breath" on anything in the drive especially the patters, & to
refit the cover as soon as I had finished, each time I looked etc.
TESTING
I have the old Norton DT (DistTest) utility that runs under DOS, that can
quickly test the whole drive, & also scandisk etc, so far it says no errors, &
it has always booted up from cold OK.
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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