All DFD1s can count to  45MHz. Difference is in range of offset that can be added or subtracted.

details below.


DFD1-TCXO1.jpg (24847 bytes)

DFD1-TCXO2.jpg (20205 bytes)

DFD1A can make a nice, accurate, inexpensive

bench-top frequency counter for HF up to 50MHz.


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A miniature digital frequency counter designed to display the frequency of operation of HF, VHF, UHF and SHF superhetrodyne (with an adjustable IF offset) and direct conversion (without offset) receivers and transmitters. Also can be used as a bench top frequency counter or built into other test equipment. Usable to 32 MHz. (8GHz with an external prescaler)

The unit uses a PIC16C71 microcontroller which has a built in A/D converter.

A/D converters are connected to 15 turn trimpots. These trimpots are used to input a frequency offset, usually equal to the IF frequency of the receiver or transmitter.

All DFD1s can count to 45MHz.

See details for the various custom units for the radio manufacturers listed above.

         The unit then measures the Local Oscillator frequency and adds or subtracts the IF frequency offset. The result is a display of the actual receive or transmit frequency.

PRESCALE mode (DFD1 only): the third trim-pot inputs a number from 1-8 which is multiplied times the computed RF frequency to counter the effect of an external prescale divider. (IF and RF resolution is degraded by the value of the external divider N. IF resolution=N*1000 Hz, RF resolution = N*10 Hz.

MODE is an additional A/D input programmed by and external resistor (or switched resistors) to display an operating mode . The modes that can be displayed are AM, FM, CW, USB, LSB, FSK, FAX or 'blank'.

The unit has two discrete inputs (open circuit or ground) from which the user can change it's function.

         ADD/SUBTRACT causes the unit to add or subtract the offset from the measured frequency. This input can be remoted from the bandswitch of band-imaging receivers/transmitters to provide correct frequency display in both bands.

         Display RESOLUTION 10Hz jumper off, 100Hz jumper on.

(This unit will not work with swept frequency applications such as spectrum analyzers as it does not average)

Several circuits have appeared in the amateur and professional literature regarding adding prescalers to increase the range of frequency counters. Any of these circuits will work with DFD when used in the PRESCALE mode. The input sensitivity is sufficient to interface directly with ECL prescalers such as the Motorola MC120XX series.

The display is a 16 character LCD. A typical display is "14.22512 MHz USB" .

The correct RF frequency is displayed regardless of the relationship between LO, IF and RF frequencies. The RF can be above or below the IF frequency and the LO can be above or below the RF frequency.

The unit is 3.2" wide x 1.4" high x 1.25" thick open frame construction, intended to be built into something else or put in a small cabinet. Power requirements are 8 to 18 volts, 20ma. (Works great on a 9 volt battery)

Check out the APPLICATION NOTES page.

How to Order


By Phone with Visa/MasterCard

By FAX with Visa/MasterCard


By Mail   Almost All Digital Electronics, 1412 Elm St. S.E., Auburn, WA 98092




  View DFD1 Instruction Manual

Digital Frequency Display kits are also available from:

Yellow LED Backlit Display module now available.

This module is the same size as the non-backlit module and replaces it directly. You will have to supply a dropping resistor to set the current from your primary power source. The forward voltage drop of the LEDs is 4V and the maximum current is 200ma. The unit lites up pretty good with 30ma. At this setting it can be powered continuously from the on-board 5V regulator through a 33ohm 1/4 watt resistor. From 12V you need an 80ohm/2W resistor for 100ma, or a 160ohm/1W resistor for 50ma.

For LED backlit module instead of regular module add $7.50

AADE has an unconditional money bank guarantee even on kits (unless destroyed during assembly).

We have a free "we'll try to fix it if you just can't seem to get it to work" policy. ($4 return S/H charge)

We offer technical assistance from 9AM to 9PM Pacific time. (usually available on weekends) 

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