Counter Specifications

HF COUNTER

Four operating counter modes, plus two A-D channels displayed:

Direct frequency counter to 40 MHz with 10 Hz resolution
Direct frequency counter with high 1 Hz resolution
Offset counter (+1650 kHz) for counting local oscillators
Offset counter (-1650 kHz) for counting local oscillators
Channel 0 (0-5V) and Channel 1 (0 - 5V) 3.5 digits
Other gate times and resolutions, with or without the low pass filter, are available to special order.

VHF COUNTER

Four operating counter modes, plus two A-D channels displayed:

Direct frequency counter to 40 MHz with 10 Hz resolution
Direct frequency counter with high 1 Hz resolution
Prescale counter to 400 MHz with divide by 10 prescaler, direct reading
Prescale counter to over 2GHz with divide by 64 prescaler, direct reading
Channel 0 (0-5V) and Channel 1 (0 - 5V) 3.5 digits
Intended for use with popular divide by 10 prescalers such as the 11C90 and inexpensive UHF TV divide by 64 prescalers such as the SAB6456A. With the recommended Prescaler the range is 70 to over 1000 MHz with a sensitivity of 10mV p-p. Unless offsets are important to you, this is probably the most versatile version for use in a bench or portable test instrument.

RECEIVER DISPLAY

Four operating counter modes, plus S-Meter display:

Direct frequency counter to 40 MHz with 10 Hz resolution
Direct frequency counter with high 1 Hz resolution
Offset counter (+1650 kHz) for counting local oscillators
Offset counter (-1650 kHz) for counting local oscillators
Channel 0 (0-5V) displayed as a 16 step bar graph, with S value S0 - S9 and >S9 displayed as A - F (see picture).

The Receiver Display with S Meter
(click picture for full size view)

COMMON FEATURES

Power Supply

+6 to 15V DC unregulated at 25mA excluding prescaler (use plugpack or battery). For Prescaler add 30mA.
Dimensions
100mm x 150mm x 15mm (Veroboard construction) - smaller with a PCB.
Input
Up to 500mV p-p. Sensitivity about 50mV, over the range 1 kHz - 40 MHz, and better between 1MHz and 10MHz. Input impedance about 3k Ohm and 10pF. Input could be improved with better preamp. VHF/UHF sensitivity is about 10mV RMS over the range 70 - 1000 Mhz, and the output is typically 1V p-p. The input resistance varies from 560 down to 30 Ohms, and the input capacitance, excluding the PCB, no more than 5pF.
Thermal
Continuous duty 0�C to 75�C
Active Devices
Atmel AT90S4433 28 pin DIL RISC microprocessor, 78L05 regulator, 74HC00, 74HC4020 and four transistors (2N7000, BC547B, BC557B, 2N3904). SAB6456A Prescaler.
Panel Connections (bench model)
HF BNC Input, Mode Switch (four position binary encoded rotary switch which plugs into programming header), plus VHF/UHF BNC Input and Prescaler On/Off switch for optional Prescaler. On rear panel: DC Power Socket, and power switch (if used).
Cost to build
Approximately $US35 - $50 for all components, less printed circuit board. Add $10 for Prescaler.
Software
Developed by ZL1BPU. Precise selectable gate timing in software loop. Two or three different gate times. Software includes a low pass data filter to stabilize the display and remove last digit uncertainty. Counter operates in binary and has binary and BCD maths for correct direct reading display in all modes. Interrupt driven A-D converter and telemetry in main loop. Software written in Assembler.
Telemetry
Six 10 bit A-D channels 0 - 5V DC (0.1% resolution). 24 bit Frequency channel 10 Hz or 1 Hz resolution. Data rate 5 - 8 frames/sec (1/sec in high resolution mode). Each frame consists of 32 bytes of data in "human readable" form. Transmitted at 19200-N-8-1. All telemetry is in binary, and does not compensate for offsets or prescalers, since this is best done in the host application.