Frequency counter and digital scale


Introduction
Current consumption 40 mA, supply voltage 4,5...5,2 V, sizes 74x35x18 mm.
It is included the mainboard (1,3GHz prescaler, former-preamplifier, counter, time base)
and display panel with a numeric LCD of eight digits, height 12 mm.

The measuring range
On the direct input 100KHz...50 MHz/at least 100 mV, displaying on 8 digits, displaying
accuracy 1 Hz.
On the divider input 20 MHz...1,1 GHz/at least 30 mV, displaying on 8 digits, displaying
accuracy 100 Hz.

The constructive solution is the one of the instruments of the pattern panel, which
offers the easy assembly on the front of a box.

It can be selected three time bases: 0,25s, 1s and 10s. In time bases's case, of 0,25s
and 1s, it can be selected four different values of FI (Intermediate Frequence), values
that can be substracted or addicted (according to the desire of the user) at the measured
value. Thus, the new value will be displayed. It also exists the possibility to select the
used single side band (SSB), and this way they addict or they substract 1,5KHz, after which
the new value is displayed. The six values (four FI and two SSB) can be independently programed
by the user with no computer, with the help of B1 and B2 buttons. K switch serves to the
selection of the counting input. If it is switched on, the direct input is available DIRECT
INPUT, where the least semnificative digit is the one of the units), and if it ain't 
switched on, the divider input is available (DIVIDER INPUT, where the least semnificative
digit is the one of hundreds), where the signal first passes through a diviser of 100. In
both cases it's displaying the decimal points after each three digits, heading from right,
from the real decimal point (effective).


Settings
All the buttons, time bases, inputs IF1...IF4, SSB+1,5KHz, SSB-1,5KHz are activs if they
are at a logical level 0, therefore, at the ground. If the time base of 1s is at the ground,
it is the active one, if the one of 10s is at the ground, than it is the active one. If none
of them is at the ground, than the active one is the one of 0,25s. At a certain time it should
be at the ground at the most only one whire (that belongs of a FI), only the one we want
to use. Obvious, one of the entrances SSB+1,5 KHz or SSB-1,5 KHz may be at the table at once,
with a FI wire.


Intermediate Frequence FI Programing
The principle is that we show the wanted value for FI with the help of B1 and B2 buttons.
This value is automaticaly memorized. After the value is memorized, it can substract VFO-IF),
addict (VFO+IF), or mirrored (IF-VFO) at the measured value by pulling the suitable wire at
the ground (IF1...IF4, SSB+1,5KHz, SSB-1,5KHz, SIGN, MIRROR). The fact that it is addicting
or it is substracting depends on the SIGN input. If it is at the table, it is substracted, if
not, than it is addicting. We start the programing by setting off the counter. Let's adjust
the time base at 0,25s (it can be 1s too, but than it increments lower). One of the IF or SSB
entrances that we want to program, must be pulled at the ground (activated). But only one of
those six must be at the ground. We press down B2 button and this way, we turn on the counter.
If none of the six entrances ain't activated (it is not at the ground), the red led will blink,
showing an error. Normally, it will display the value already memorized from a previous cycle of
programing (the value can also be zero). We hold up B2 button. From now on, with B2 we increment
and with B1 we decrement the displayed value. The advance is progresiv, meaning that the first
time it increments only the digits of the units, than only the decimal digit, than only the
hundreds digit, and so on. If neither B1, nor B2 buttons aren't switched on no more, than
after about three seconds, the display is turning off for a short time (it blinks). This means
the memorising of the displayed value. If the value is not suitable, the programing is resuming
by pushing B1 or B2 buttons (at a certain moment only one of them). The incremention will
start again from the units and it will go on progresiv, but starting already from the value
new displayed. The process is repeating until the reach of the wanted value. This aspect ain't
optimized because it is used relatively rare, that's why it ain't quite easy from the first
try.



General Reset
Let's turn off the counter. Now the circumstances of the entrances doesn't matter. We pressed
down B1 and B2. This way we turn on the counter. The led will blink, meaning that all the
values IF and SSB are being erased. We shut down the counter. At the next turning on (normal)
all the IF and SSB values are already erased.


Observations
1.) Any FI value is addicted or substracted at/of the measured value if the suitable entrance
of that FI is at the table. For example: if we measure on the direct input (so K is pressed 
down) 3.955.000 (Hz) and we memorized in FI1 455.000 (Hz), than putting at the ground the FI1
entrance, it will poste 4.410.000 (Hz). If we activate SIGN entrance too, (we pull it to the
ground), than it will poste 3.500.000 (Hz).

2.) If we measure on the divider input (K is not pressed down), let's say 28 MHZ, on the 
display it will appear 28.000.0. The last two zeros can not be seen because of divising with
100. At the FI programing it must not be taken in consideration the decimal points. The counter
works only with entire numbers and it can't previously know if a certain FI value we will use
for the direct input or the divider input (where the signal that get's to be counted is a
hundred times smaller). Let's adjust FI2 at 1.116.000 value. This way, if SIGN isn't at the
ground, it will poste 28.000.0 + 1.116.000 = 144.000.0.

3.) If, in case of FI programing we performed an overflow (the number has been incremented
at a value that can't no more be displayed on 8 digits, for example 102.345.000) or an 
underflow (the number has been decrementated at a negative value), than it will be seen only
the last eight digits with decimal points between (0.2.3.4.5.0.0.0.). The decimal points
signify the overflow or the underflow. It ain't sure that a overflowed or negative value we
can restore out of B1 or B2 buttons. This is because of that progresive counting. In this case
we must use GENERAL RESET, that erases all the FI and SSB values.

4.) In case of normal function it may also appear a overflowing, if we measure, for example
40 MHz on the direct entrance, and a FI is adjusted at 65 MHz, and the addiction is activated.
Because 40 + 65 = 105 MHz, it enters no longer on the display. Or if the substraction is
activated, we have a negative result: 40 - 65 = -25 MHz, and we obtain a underflow. We also
obtain overflow if, for example, we measure 20 MHz on the direct input, but with time base of
10s, in fact enters in the counter 200 millions of impulses, which can't be displayed on 8 
digits (it practically display only the 8 least signifiant digits with decimal points between
them).

5.) If we work with a mirrored domain (FI - VFO), and if this result is negative, for accurate
displaying it must activate (putted at the ground) MODULUS entrance. For example, 40 - 65 =
-25 (negative value with underflow) but with MODULUS aplicated it will poste the effective, 25.


Supply
From a stabilised source of current of 4,5...5,2V. On the mainboard, in the supply point, is
mounted a zenner diode of 5,6V, mented to filtrate the peak voltage that would comme from the
source. So the supply with appropiate voltage of 5,6V is not well recomended, because it will
begin to open the zenner diode. It is recomended the use of a stabilizer type 7805.