This simple counter is useful for frequency measurements of various wireless equipments, especially transmitters, receivers and signal generators in VHF/UHF band.
Display range: 0,0 to 999,9 MHz, resolution 0,1 MHz
Correct rounding, reduced blinking of last digit
Fast measurement - short measuring period
High input sensitivity in VHF/UHF band
Switchable intermediate frequency offset for use with receiver
Technical specifications :
Supply voltage: 8-20 V
Supply current: typ. 80 mA, max. 120 mA
Input sensitivity: max. 10 mV in 70-1000 MHz range
Measuring period: 0,082 sec.
Display refresh rate: 49 Hz
Schematic diagram :
R1 - 39 k
R2 - 1 k
R3-R6 - 2,2 k
R7-R14 - 220
C1, C5, C6 - 100 n mini
C2, C3, C4 - 1 n
C7 - 100 u
C8, C9 - 22 p
IC1 - 7805
IC2 - SAB6456 (U813BS - different pin layout, not tested, also maybe R1 value need to be changed)
IC3 - PIC16F84A programmed + socket
T1 - BC546B
T2-T5 - BC556B
D1, D2 - BAT41 (BAR19) - may be ommited
D3 - HD-M514RD (red) or HD-M512RD (green), 4-digits multiplex driven LED display from HP, or four standard 1-digit LED displays
X1 - 4.000 MHz crystal
BNC input connector
To use with a receiver as a digital scale, close the -10,7 pins.
IC3 program download: countr.hex http://pira.cz/counter.hex
Programmer settings: Oscillator: XT, WDT: on
For additional changes (eg. IF frequency offset change): counter.asm http://pira.cz/counter.asm
The SAB6456 description :
The SAB6456 is a prescaler for UHF/VHF tuners. The circuit has an input frequency range of 70 MHz to 1 GHz, has high input sensitivity and good harmonic suppression. With lower sensitivity it's usable down to 3 MHz.
The circuit comprises an input amplifier, a divider stage and an output stage. The divider stage may oscillate during no-signal conditions but this oscillation is suppressed when input signals are received. The voltage-edges of the output signals are slowed internally to reduce harmonics in the television intermediate frequency band.
Kepada temen-2 yg pernah membuat frequensi counter ini, tolong disharing pengalaman dan saran nya. Soalnya aku lg coba buat. ( supaya bisa meminimalisir kesalahan dan buget tentunya