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G8MNY > TECHNI 05.02.20 11:45l 222 Lines 11308 Bytes #999 (0) @ WW
BID : 43868_GB7CIP
Read: GAST
Subj: Watson 'Hunter' Counter Mods
Path: DB0FFL<OE5XBL<F1OYP<ON0AR<OZ5BBS<CX2SA<OK2PEN<N3HYM<KA3BVJ<AB0AF<
F1OYP<JH4XSY<JE7YGF<GB7CIP
Sent: 200205/1035Z @:GB7CIP.#32.GBR.EURO #:43868 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Update Nov 16)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I have bought a damaged one of these small 3GHz handheld counters, & I went
about repairing & upgrading it as there were a lot of components & switch
options possable that were missing on this bottom of the range model.
On point about this counter, it does now actually count what it shows & at VHF-
UHF the resolution (what it counts) may be in 4 8 16 32 64 or 100Hz steps
depending on what the prescaller system is doing.
MODIFICATIONS DONE (in order of importance!)
1/ Add UHF clipping diodes across the BNC socket.
2/ Stop LCD rubbing marks from the lens casing. (& future smashed LCD)
3/ Add bargraph signal meter.
4/ Add low battery indicator.
5/ Add gate time push button, to give 0.1s 2s 1s & 5s gate times.
6/ Add "no prescaler" RF path to read 1 - 30MHz.
With 5 & 6 you can read 1MHz - 30MHz down to 0.1Hz & 30MHz - 3GHz down to 10Hz.
But calibrating the crystal osc to high accuracy even short term is not easy.
There is only 2 other features according to the LCD graphics..
a) switchable filter
b) a period timer.
I did not understand the wiring for a) & I don't think the PCB supports b).
Be warned it as all very small Surface Mounted Devices! So other than the input
clipper protection & LCD case modifications, I do not recommend the other
modifications unless you are fairly competent with soldering SMD components on
a busy SMD board!
O R I G I N A L M O D I F I E D
.³~~³. DC .³~~³. DC
ÚÄÄÁÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÁÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ ³ ³ ³
³ ³ ³ ³
³ WATSON Hunter o ³ ³ WATSON Hunter o ³
³-----------------------------------³ ³-----------------------------------³
³| Frequency PRESCALE HOLD |³ ³| Frequency PRESCALE HOLD |³
³| MHz|³ ³| MHz|³
³|[] [] [] [] [] [] [] [] [] [] |³ ³|[] [] [] [] [] [] [] [] [] [] |³
³|[].[].[].[].[].[].[].[].[].[]. |³ ³|[].[].[].[].[].[].[].[].[].[]. |³
³| |³ ³| _ - = ð ~ ÚÄ¿|³
³| |³ ³| signal _ - ð ~ ð ð ð ð ð ³X³|³
³| |³ ³| _ - = ð ~ ð ð ð ð ð ð ð ð ð ÀÄÙ|³
³-----------------------------------³ ³-----------------------------------³
³ 10MHz-3GHz/50ê Frequency Counter ³ ³ 1 MHz-3GHz/50ê Frequency Counter ³
³ Power Cal³ ³ Power Pre Cal³
³ On Hold 0 ³ ³ On Scale Hold Time 0 ³
³ [] ³__³ ³ ³ [] [] ³__³ ³__³ ³
³ ³ ³ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
\³/___ ____ ___ _______ ___ \³/___ ___ ____ ___ _________ ___
À´Preôö100ô ö8ƵCounterôLCD³ À´LimôPre³ o´ö100´o ³ ö8Ƶ Counter ôLCD³
ÀÄÄÄÙÀÄÄÄÄÙ³ö16³ÀÄÄÄÂÄÄÄÙÀÄÄÄÙ ÀÄÄÄÙÀÄÂÄÙ\oÀÄÄÄÄÙo/³ö16³ÀÂÄÂÄÄÂÄÄÂÙÀÄÄÄÙ
ÀÄÄÄÙ Hold ÚÄÁÄ¿ ³ÚÄÄÄ¿ ³ ÀÄÄÄÙ ³ ³ Batt³
³Det³ À´AmpÃÄÙ ³Hold Time
ÀÄÂÄÙ ÀÄÄÄÙ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
FRONT END FAULT
The fault was a blown up front end SMD MIMIC (A06), as there is NO input
protection fitted!
As I could not find a replacement device to hand, I used a scrap cellphone
preamp SMD NPN & made up an amp with just an additional bias R (22k). This NPN
fitted over the 4 pad A06 OK, with the bias SMD 22k (selected to give the same
current as the 2nd A06 stage) & placed over the NPN. It all worked well & a QRP
2400MHz Tx was measured OK with the search aerial alongside.
ORIGINAL REPAIRED
ÚÄ´ÃÄÄÄÂÄÄ+5V ÚÄÄ´ÃÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄ+5V
³ 100ê °° °° ³ 100ê °° °°
³ ³ In Gnd ³ ÚÄ22kÄÅÄ´ÃÄ>U2 B unused
(o)Ä´ÃÄ´>ÁÄ´ÃÄ>U2 (o)ÄÄÂÄÄÄÂÄ´ÃÁÄÄÄ´<
BNC³ U1º Gnd Out ³ _³_ _³_ e³ E C
³ º °° °° ³ \_/ /_\ ³ °° °°
ÀÄÄÄÄÄÐÄÄÄÄÄ PCB PADS ÀÄÄÁÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄ PCB PADS
1/ To reduce the chance of a re-occurrence, I added 2 UHF clipping diodes wired
across the BNC socket. 1N4148 diodes will do if you have no better.
2/ I had heard of someone breaking the display, this makes the unit a total
write off!
Looking at my display, I could see tell tail marks (lines) where the LCD had
been rubbed by the sharp case lens metal stamping edge.
C_L_E_A_R__P_L_A_S_T_I_C
=======<________________________>============
Embossed`========ð ð=='
Metal Case ^sharp edges^
°°°°°°°°°°°°°°°°°LCD
________________³__________XTAL_³__________PCB
To remove the sharp edges, use a small modelling knife held parallel to the
case so that the lens can't be damaged. Then firmly drag the blade over the
raised edges, scraping off the sharpest part of the edge. Go all around the
raised lens stamping edge, make sure that there are no proud part that could
put concentrated pressure onto the LCD glass. (e.g. when dropped)
3/ To make the bargraph display work, add a uhf diode to half of D2. I used a
schottky one across just 2 of the 3 SMD diode pads. Note DIODE Polarity! Also
add a 1n instead of adjacent missing R.
ÄÄÄÂÄÄ+5V °°Ä¿
U2 100ê _³_
Ä´ÃÄÂÄ´>ÄÁÄÄ´ÃÄ>U3 Prescaler °° D2 /_\
_³_ ³
/_\D2 oÄÄÄÄÂÄÄÄ°°ÄÙ
ÀÄÄÄÂÄÄÄ>U9 IC °° PCB PADS
===1n 1nÄÁÄ
Á ÄÂÄ
°°
3/ By moving the HOLD push button from mounting holes "SW6" to the left over-
lapping "SW4" holes, there is then room to fit an identical button in "SW7"
position. ( ( () ) () )
SW4SW5 SW6 SW7
Then you can get the counter to change the gate time from the default 0.2S to
the 3 others possible times & hence the display resolution.
You then have to file the existing case button hole to a long slot. This is
quite simple to do with a set of sharp needle files, but time consuming! I then
cut & filed an ally blank to between the buttons & glued that in place.
4/ This needs 1 small preset pot, 1 SMD NPN (L-4), 2 SMD Rs, & a zener. Looking
at the circuit I found the zener needs a series R to work properly, & I
selected one on test to make my pot have useful setting range.
_____ SW2 D1
+5V <ÄÂÄÄÄÂÄÄ´78L05ÃÄÄÄÄÄÄÂÄÄÄÄÄo\ÄÄÂÄ´<ÃÄÄÄo+ 9-12V
³ ³ ³ U10 ³ 100k X ÚÄv_Û
³ 10k ÀÄÄÂÄÄÙ ZD1_³_ +_³_ ³ ³Switched
³ R32 ³ 2.7V/_\' _Ü_ ³ ³Power
U9<ÄÄ)ÄÄÄ´ ³ ³ Ü ³ ³Jack
³ \³ ³ R31 ³ ³ ³ ³
³ Q7 ÃÄÄÄ)ÄÄÄ10kÄÄÄ´ X ³ ³
³ e/³ ³ ³ ÃÄÄÄÙ ³
C1=== ³ ³ LOW VR1 R2 ³
100u³ ³ ³ BATT 22k 56ê ³
ÄÁÄÄÄÁÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÙ
The battery does not give > 5V, so the regulator is not actually regulating
when on battery supply! I suspect there should be more than 4 AA cells (but no
room) if the supply needed to be properly regulated for more accurate work the
5x AAA Nicads might work better! The counter is actually quite accurate for its
simple uncompensated xtal system.
There is a danger if connecting the counter to an earthed supply while having
the BNC connected to other earthed kit. This is because the nicad battery
charging is via a negative change power switch arrangement. During insertion
the 12V will be placed across the 5V battery until the switch breaks the
negative battery lead. This may only last a very short time but currents >5A
can flow & could damage leads, PCB track & eventually the battery! [good for
battery for a few seconds :-) ]
LAYOUT BNC
DC .³~~³.
ÚÄÂÄÂÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÁÄÄÁÂÄÄÂÄ¿
³o³ ³ ³ VR1 ____ ³____³ ³o³ U1 & U2 Input Preamps
³~ ³ ³ ³ U7 ³ U1 ~³
³ ÀÄÄÙ ÀÄÄÄÄÙ ³ U3 3GHz ö100 Prescaler
³ D2 U2 ³
³ ³ U4 & Q3 No Prescaler bypass amps
³ ÚÄÄÄÄÄÄÄÄ¿ ____ __ ³
³ ³ ³ ³ U6 ³ U4 ;³U3³:³ U5 Gated ö8 & ö16 prescaler
³ ³ U9 ³ ÀÄÄÄÄÙ 'ÀÄÄÙ'³
³ ³ ³ Q2 ³ U6 Overflow Counter decoder
³ ÀÄÄÄÄÄÄÄÄÙ ÃÁÁÁÁÁ´ Q1 ³
³ X1 ³ U5 ³ _ ³ U7 Gate pulse counter
³ Q7 TTTTTTT :³_³]³
³ U10 ³ U9 Counter IC & display driver
³ ___³
³ Batt³___³ U10 5V regulator
³_ _³
³o³ ³o³ X1 4.19407MHz Crystal
ÀÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÙ
5/ A far more complex modification is to add the 2 HF amplifiers, missing for
the no prescaler mode, & move/add the missing switches to control it.
+5VÄÄÄÄÂ 7,3,2ÚÄÄÄÄÄÄÂÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
100ê ÚÄÄÄÁÄÄÄ¿100ê 6k2 ____ ³
ÄÄ´>ÄÅÄÄ´ÃÂÄÄ´U3 ö100ÃÄÄÁÄ´ÃÄÁÄ´< Q1 ÃÄ330êÄ)ÄÄÄÄÂÄ+5V
U2º ³ ³ 1ÀÄÄÄÂÄÄÄÙ4 e³ ³ o ³ oÄÄÄ>U9
Ð ³ 100k 5³7 Á ³ o <ÄÄÙSW3ÚÄÄ>o
³ Á Á ÚÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄ)ÄÄÄÄÄÄÙ Á
³ R13 R14 ³ 1,7,9ÚÄÄ+5V
R ÚÄÄÄÄ¿ 310ê 100k ____³ ÚÄÄÄÄÄÁÄ¿11
2k2 100k ÃÄÄÁÄÄÄ´ÃÄÁÄÄÄ´< Q3 ÀÄ´ U5 ö8 ÃÄÄÄ>IC U9
ÀÄÄÄ´ÃÄÁÄÄ´< C12 e³ 2³ ö16 ÃÄÄÄ>COUNTER
C9 U4 ³e Á ÀÂÄÄÄÄÄÄÙ12
Á Á3,4,5,6
Again instead of a mimic amp U4 I used a biased HF NPN (L-4). But I found that
I had to add a series R of 2k2 to C9 so that it did not load U2's output to
pre-scaler IC U3. I re-used the changeover power switch SW2, as the SW3
changeover & I found a smaller make switch for the SW2 power switch. Again I
had to make new hole in the case for SW3, & drilled then filed a matching
rectangular hole.
N.B. Below 1MHz the counter software stops the display from counting. And there
are tricks done in the count, so the resolution is not that displayed! eg. at
10MHz there are only 0.4Hz steps on the 10 sec gate, not 0.1Hz.
See other tech buls "Old Venner Counter Type TSA3334", "PIC Freq Counter Mods",
"Marconi Counter Type 2434A", "198kHz Off Air Standard", & "Off Air Lock for
Ref Osc" & "Calibrating Frequency".
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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