1 GHz Counter

This simple counter is useful for frequency measurements of various wireless equipments, especially transmitters, receivers and signal generators in VHF/UHF band.

1 GHz Counter Features

Display range: 0,0 to 999,9 MHz, resolution 0,1 MHz
Correct rounding, reduced blinking of last digit
Over-range indication
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

counter.gif (8761 bytes)

Parts list

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 needs 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.

1 GHz Counter IC3 program download: counter.hex
Programmer settings: Oscillator: XT, WDT: on
For additional changes (eg. IF frequency offset change): 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.

In this circuit the prescaler divides the input signal frequency by 256.

Printed circuit board

Important!
There are two pin connection versions of the SAB6456. In the schematic diagram there is drawn a standard pin connection as provided by Philips datasheet. The PCB is proposed for both versions.

PCB - standard pin connection of SAB6456

PCB - different pin connection of SAB6456

The display is placed vertically on the PCB.