This photo show the PCB backside of the transendent frequency counter. The LCD display is placed on the front side. Very small unit and still so powerful. Transcendent Frequency Counter
1 Hz - 2.5 GHz with Blue 2x16 LCD display

This is a top quality project designed to obtain maximum performance.
The hardware and software has been pushed to reach the frontier of technology.
The transcendent is not only a frequency counter, it is a corner stone in your successfully constructions.

  • The transcendent counter has two input channels (low frequency and high frequency).
  • Channel Fin Low: 1 Hz to 50 MHz with resolution of 1 Hz
  • Channel Fin High : 5 MHz to 2.5 GHz with resolution of 100 Hz
  • High sensitivity inputs typ -25dBm to -10dBm (12mV to 70mV) both channels
  • Channel Fin Low : Input Impedance > 1 M Ohm
  • Channel Fin High : Input Impedance 50 Ohm
  • Both inputs are protected for transients and ESD over voltage
  • Add or subtract seven pre-set IF frequencies (0 Hz, ±455 kHz , ±10.7 MHz and ±21.4 MHz)
  • Add or subtract one self defined IF frequency from -999.9999 MHz to +999.9999 MHz
  • Measurements can be transmitted to computer with RS232 communication
  • ON/OFF RS232 option, for extreme silence
  • PIC version with on-board 13.00000 MHz reference crystal
  • PIC version with external 10.00000 MHz reference signal (GPS time base)
  • No pre- or post-flank errors
  • Display with blue background and white characters, 2 lines 16 Chars
  • Software controlled contrast of display
  • Three buttons controlled menu system for controlling all options and settings
  • Power down memory for all menu options and settings
  • Transcendent frequency counter for the those who choose top quality
  • Power supply +9 VDC to +18 VDC (+5V possible with minor modification)
  • Low current consumption typ 30 mA
  • Board size = 3.2" x 1.9" (81 mm x 48 mm)
  • This project comes only in a KIT version, see more details below

  • All contribution to this page are most welcome!

    This project is the most complex of all my frequency counter projects.
    A frequency counter is one of the most important measuring tool when it comes to RF electronic.
    This frequency counter has very high performance, wide frequency range and many new software functions.

    To achieve the high performance I decided to split the rf inputs into two separate channels.
    Transcendent, only acurate timimng accepted Each channel has been designed to deliver maximum performance and high sensitivity.

    The Fin Low measure frequencies from 1 Hz to 50 MHz with a resolution of 1 Hz.
    The Fin High measure frequencies from 5 MHz to 2.5 GHz with a resolution of 100 Hz.

    With a few pushes on the buttons, the Transcendent frequency counter changes input channels (more details under software section).
    The software and hardware is very complex, still the project has few parts and is easy to assemble and operate.

    The counter is based around a PIC processor and a display with blue background and white characters.
    The PIC is a 16F870 circuit which controls the counting. A two lines and 16 chars HD44780-display present all information.

    Reference oscillator
    The Transcendent frequency counter comes in two versions.
  • On-board 13.000 MHz crystal (picture at top), or
  • External 10.000 MHz reference input.

    The reason of using an external 10.000 MHz reference frequency, is because it is common among reference oscillators, as rubidium oscillators or HP Z3801 GPS locked frequency source.
    The Transcendent frequency counter has been tested with a GPS reference with the accuracy of 0.1 e-12 (1 Hz error at 10000 GHz). The Transcendent worked perfectly.
    Click here to view a larger format
    The picture at right show my own 10.000 MHz Atom ref oscillator, based on the well known Efratom Rubidium LPRO-101.
    It takes 2-3 minutes for it to lock, and the accuracy is then 0.5 e-9 (0.5 Hz error at 1 GHz).
    I have a RGB-LED at top right corner that starts to blink green when the unit is locked. (Red when unlocked.)
    After 20 minutes the efratom is stable in temperature and the LED gives a constant light. The accuracy is then 2 e-11 (2 Hz error at 100 GHz).
    To the left you can see my Transcendent counter with the two input connectors. I have three buttons with integrated blue LEDs, to control the menu.
    With this little unit, I have both a 10.000 MHz output reference signal and a frequency counter, which use the 10 MHz reference for accurate measurement.

  • Hardware and schematic
    The main part of this project is a PIC16F870, LCD and a prescaler LMX2322.
    The LCD is a standard 2 line 16 chars display connected in 4-wire mode to the PIC.
    Click here to view a larger schematic At the bottom you will find a stable 13.000 MHz crystal. Capacitor C10 is variable and is used to calibrate the gate timing of the transcendent frequency counter.
    There is two frequency inputs. Fin High works with frequencies from 5 MHz to 2.5 GHz.
    The Fin High is connected to a prescaler and the input impedance is 50 ohm. The input is transient protected with the diode D2.
    The other input Fin Low is for frequencies from 1 Hz to 50 MHz. A FET transistor with very high impedance (>1M ohm) buffer the input signal.
    The input is transient protected with the diode D1. A second transistor Q2 works as an amplifier and add gain to the system.

    In the schematic I have added my measured DC bias voltages around the Q1 and Q2. The bias voltage can vary a bit due to natural spread.
    I advice you to see the bias voltages as guide, not as exact measurements.
    The output RA3 from the PIC choose which input (Fin High/Fin Low) to use for measurement.
    The output RC6 from the PIC send data to a computer. Q3 and the parts around handle the voltage transformation for matching the RS-232 line.
    The output RA5 from the PIC (J9) is the output to a buzzer (speaker). Every time a button (SW1, SW2, SW3) is pushed a short beep will be heard from the buzzer.

    There is three controlling buttons to handle the software and menu options.

    Pin 2 is the switch SW1 (J6) which guide you through a five steps menu system. Pin 3 is the switch SW2 (J7) which you use to INC choices in the menu system.
    Pin 4 is the switch SW3 (J8) which you use to DEC choices in the menu system. (more details under software section)

    Slim construction with display on front side and electronic parts on the back side. A jumper J1 is added to choose if you want strong backlight or not. If jumper J1 is connected you will have strong backlight.
    If jumper J1 is disconnected the LCD will have soft backlight, because a low current will pass through R5.

    The output RC2 from the PIC drive the display contrast voltage. The voltage at pin 3 of the display should be around 0.5 to 1.5 V.
    The contrast voltage can be set from the menu system. (more details under software section)

    No pre- or post-flank errors!
    This frequency counter use intelligent gating system and special designed algorithm to detect eventual pre or post-flanks in the counter system.
    The result of this, gives a very accurate and stable frequency counter which you will only find in expensive commercial frequency counters.

    What is the reason to add/subtract the IF frequency ?
    Radio receivers works with an intermediate frequency (IF).
    One reason of having a intermediate frequency is to optimise the filtering in the receiver.
    The formula below show the relationship between the receiving frequency, internal VCO and the IF :

    Receiving Frequency = VCO ± IF
    (Receiving frequency = internal oscillator of the receiver ± intermediate frequency)

    If we connect a frequency counter to the VCO (internal oscillator) we will not be able to measure the receiving frequency, due to the IF value.
    To be able to read the receiving frequency on the LCD display of the frequency counter, we must be able to add or subtract the IF value.
    The transcendent frequency counter has seven pre-defined intermediate frequencies (IF), 0 Hz, ±455 kHz, ±10.7 MHz, ±21.4 MHz.
    The 0 Hz, is used when you want to measure the exact incoming frequency without any mathematical manipulations.

    There is also one self-defined intermediate frequency (IF) which can be set from -999.9999 MHz to +999.9999 MHz.
    With the switches SW1, and SW2, you can easy choose which intermediate frequency (IF) you wish to add for the measurements.

    I will explain with an example.I need that counter to win...
    Below you can see my measurement of the internal oscillator in my radio receiver. The internal oscillator is 100 MHz.
    I step with SW1 and SW2 threw the different IF options and you can see that the frequency presented on the display changes value due to which IF system I choose.
    In this receiver the intermediate frequency (IF) is manufactured to be +10.7 MHz, which means that I actually receive at 110.7 MHz.
    I select the IF to be +10.7000 MHz and the presented frequency on the display becomes 110.7 MHz, which is the receiving frequency...great!

    You can also see that when intermediate frequency (IF) is set to +000.0 (zero), the true measured frequency of 100 MHz is presented on the display.
    You can also see my self-defined intermediate frequency which I have set to 5.5 MHz (used for sound carrier in video signal).
    (more details about IF under software section)

    Just hook up the counter with your receiver or transmitter oscillator and enjoy.
    Detailed information about receiver IF and OSC can be found by clicking this link.

    The desoldering wick is a flattened, braided copper sheath	Assembly
    The soldering of this unit is pretty basic. I will explain how to assemble this KIT step by step.
    The PCB is a factory manufacture PCB with high quality, which makes the assembly and soldering simple.
    Please do not be scared for soldering smd parts. Smd is not more difficult than hole mounted parts if you use the correct skills and tools.
    Important tools are good light, soldering tool with thin tip, magnifying glasses, tweezers, thin soldering lead, wick impregnated with rosin and calm mind.

    The de-soldering wick is a flattened, braided copper sheath looking for all the world like shielding on phono cord (except that the shielding is tinned) without the cord.
    The wick is impregnated with rosin. Place the wick over the legs or bridges of the circuit.
    The wick is then heated by the soldering iron, and the molten solder flows up the braid by capillary action. After that, all bridges will be gone and the circuit looks perfect.
    Thin soldering lead and wick impregnated with rosin are included in the KIT.
    Click here to see photo and read more examples how to solder SOIC and smd components.

    There is ten steps for mounting the parts. Below I describe them with picture and instructions.
    Some picture can be magnified by clicking onto the picture.

    Top and Bottom layer of the PCB

    Click the image to see full scale image! Click the image to see full scale image!
    1.) IC2 LMX2322
    Place the LMX2322 to the PCB as accurate as possible. Magnifying glasses are welcome.

    Place the LMX 2322 to the PCB and by soldering fixate the top right leg and the bottom left leg. I use a magnifying glass to make sure it is places in line with the PCB pattern. From the picture above you can see that all legs are placed in line with the PCB pattern, and it looks good.
    2.) IC2 LMX2322
    Solder all legs and make sure you have no bridges between legs

    When the corner legs are fixed, solder the rest of the legs. If you get lead bridges between legs, you can easy clean it up by using the wick. Place the wick over the bridges and heat the wick with your soldering tool. The wick will absorb all overflow lead. Bridges will be gone and the circuit looks perfect.
    3.) X1 13.000 MHz Crystal
    Solder the crystal, make sure it is oriented correct

    Place the crystal to the PCB and solder all four pads.
    4.) C10 Calibration capacitor
    Solder the trimmer cap for trimming the gate time

    Mount the trimmer capacitor as picture show.
    5.) Q1, Q2, Q3
    Solder as picture show

    Mount Q1, Q2 and Q3 as picture show.
    6.) D1, D2, D3
    Solder as picture show

    Mount D1, D2 and D3 as picture show.
    7.) Capacitor
    Solder all the smd capacitors.  Use a tweezer to hold the smd parts

    Mount smd capacitors below :
  • 22 pF = C9
  • 1 nF = C6, C7
  • 100 nF = C2, C3, C4, C5, C8, C11, C12, C13, C14
  • 2.2 uF = C15 (Orange line = plus)
  • 47 uF = C1 (Black line = minus)

  • 8.) Resistor
    Solder all the smd resistors.  Use a tweezer to hold the smd parts

    Mount smd resistors below :
  • 100 = R5, R18
  • 402 = R10
  • 1 k = R7, R8, R17
  • 3.3 k = R1, R2, R3, R4, R14, R15
  • 10 k = R11, R13
  • 20 k = R9
  • 42 k = R12
  • 100 k = R16
  • 1 M = R6
  • 9.) All smd parts mounted
    Click to enlarge !

    At this point all smd parts has been mounted. Click the pic to enlarge.

    10.) Hole mounted parts
    Click to enlarge !

    Mount hole mounted parts below (Click the pic to enlarge):
  • 28 pin IC socket = IC1 (only socket, wait with PIC )
  • 2 pin header = J1, J2, J5, J6, J7, J8, J9, J10
  • 3 pin header = J4
  • 16 pin header = J3 (mount J3 on backside of PCB)
  • 78L05 = V1
  • LCD 16x2 Char Blue type (backside of PCB)
  • PP3 Connector for 9V battery (J1)
  • jumper (J2)

  • I advice you to make a few test before you put the PIC16F870 into its socket.
    Perform an visual inspection of the PCB to make sure you have no soldering bridges or misplaced parts. Make sure the PLL is placed in correct direction.
    Apply power to J1 and control that the display gives a blue backlight. You will not see any text yet, since the PIC is not connected.
    (Do not forget to remove the clear plastic film which protect the front of the LCD Display.)

    Location of test points Power to socket
    Measure the voltage between pin 8 (GND) and pin 20 (Vcc) of the PIC16F870. The measurement should show +5 V.
    Measure the voltage between pin 8 (GND) and pin 1 (Reset) of the PIC16F870. The measurement should also show +5 V.

    Disconnect power and mount the PIC16F870 into its socket.
    Apply power and control that you see the text on the display.
    Measure the voltage between GND and pin 3 (J3) of the display. The measurement should show 0.5 to 1.5 V.

    Power to pre-amplifier
    Measure the voltage between GND and pin 11 (RC0) of the PIC16F870. The measurement should show around 2.7 V.
    Measure the voltage between GND and collector Q2. The measurement should show around 2.3 V.

    Power to FET-amplifier
    Enter menu and set the input to Fin Low (more details under software section).
    Measure the voltage between GND and drain Q1. The measurement should show around 3.3 to 3.6 V.
    Measure the voltage between GND and source Q1. The measurement should show around 1.2 to 1.7 V.

    When a 13 MHz crystal is used, the calibration of the counter is made by the variable capacitor C10, which will be able to change the gate time some ppm. The transcendent frequency counter is supposed to be a measuring tool with good accuracy, so a good calibration is needed. Unfortunately most people has no good reference to calibrate against.

    You can use a good TCXO or equal with high frequency tolerance as the 12.800 MHz Crystal Oscillators NDK (NKG3001B) which has been trimmed to give ±0.1 ppm tolerance. more details below
    Apply +5V to the VCTCXO and measure the output frequency.
    All you need to do is to tune C10 until you reach 12.800.000 on the display.
    Now you have frequency counter where the accuracy is ±0.1ppm (±10Hz at 100MHz).

    measuring 100 MHz input signal, and the IF is set to zero to show the exact incomming frequency. PIC Software
    Let's have a look of the different menu systems and choices of the Transcendent frequency counter.
    All settings are made by three switches SW1, SW2, and SW3.
    The unit will always remember the last settings even if power is switched off.

    SW1 (J6) guide you through a five steps menu system.
    SW2 (J7) is used to INC value. SW3 (J8) is used to DEC value.

    1.) Main menu for presenting frequency measurement

    Pressing SW2 and SW3 will change Intermediate Frequency (IF) option.

    After power up, you will enter the main presentation menu.
    Picture above show you the main menu for presenting the frequency measurement. In this case, I have applied a 100 MHz signal to the counter.
    The Intermediate Frequency (IF) is set to +000.0, and the true measured frequency of 100 MHz is presented on the display.
    If you press SW1 you will enter next menu choice, see info below.

    2.) Selecting input source

    Pressing SW2 select input Fin Low

    Pressing SW3 select input Fin High

    This menu select input signal source.
    The display will show you the selected input source, see picture above.
    By pressing SW2 you select input Fin Low, and by pressing SW3 you select Input Fin High.
    If you press SW1 you will enter next menu choice, see info below.

    3.) Self defined IF frequency

    Pressing SW2 (INC) or SW3 (DEC) will change Intermediate Frequency (IF) value.

    As I mentioned above in the IF section, you have one self defined intermediate frequency (IF). The intermediate frequency can be set from -999.9999 MHz to +999.9999 MHz
    By pressing SW2 the Intermediate Frequency (IF) value will increase with 100 Hz steps, and by pressing SW3 the Intermediate Frequency (IF) value will decrease 100 Hz steps.
    The picture above show you the Self defined IF frequency menu. The present value is +0.0000 MHz and by pressing SW2 the value increments.
    When the value reach 0.0100 MHz SW3 is pressed and the value starts to decrease back to +0.0000 and then to a negative value of -0.0002 MHz.
    SW2 is then pressed to increase the value back to +0.0000 MHz.
    With the two buttons SW2 and SW3 you can set any Intermediate Frequency (IF) very easy.
    The longer time a button is pushed, the larger increment/decrement you will get.
    It takes only a few seconds to sweep over the hole range from -999.9999 MHz to +999.9999 MHz.
    All settings of the transcendent counter will be stored during power down.
    If you press SW1 you will enter next menu choice, see info below.

    4.) RS232 Option

    Pressing SW2 activate RS232 line to ON

    Pressing SW3 deactivate RS232 line OFF

    This menu activate or deactivate the transmission of RS232 data to computer.
    The display will show you the selected RS232 option, see picture above.
    By pressing SW2 you activate the RS232line to send data, and by pressing SW3 you deactivate RS232 line which will be silent.
    Deactivation of RS232 gives an extreme silent counter. There will be very low noise levels on the input lines and power lines.
    If you press SW1 you will enter next menu choice, see info below.

    5.) Display contrast

    Pressing SW2 (INC) or SW3 (DEC) will change the contrast of the LCD display.

    This menu set the contrast of the LCD display.
    Picture above show you the menu for changing contrast level
    By pressing SW2 the contrast level will increase, and by pressing SW3 the contrast level decrease.

    If you press SW1 you will go back to main menu.
    The different menu options are easy to learn and it takes less than 10 minutes to master them all.

    Windows software
    The picture below show a measurements of a NOOA Satellite receiver which operate at the frequency of 137.85 MHz.
    The input is Fin High and the frequency is displayed with different type of skin.

    The software is FREE and you can change the skin as you wish.

    Download windows software & Source code

    The windows software is pretty simple. First you choose the input com port.
    I have extended it to 4 because lap tops (using USB to RS232 converter) often get com port 3 or 4. After choosing comport you simply press start.
    The type of input is displayed in the frame Input. In this case it is Fin High.
    If you wish to, you can change the display colour by pressing "Display colour" button and choose other skin. You can of course make your own skin, as long as the gif picture (included files) has the same size as the examples. The picture above show some of them.
    The windows software and the VB code is free to use. If you are skilful programmer (which I am not) I will be happy to place your software here.

    Transfer protocol:
    The communication between the frequency counter and the computer is based on standard serial communication.
    The serial RS232 link use 1200 baud, 8 bit, no parity and one stop bit (1200,n,8,1).
    The transfer protocol is very simple. Each package of data consist always of 5 chars.
    The counter buffer is sent in hex format with hex low first and hex high last.
    The last char represent the input mode. 00 = Fin Low and 01 = Fin High.

    Example: The counter measure 50.000.000 Hz
    50.000.000 dec = 02 FA F0 80 hex
    The 5 transmitted chars will be 80h, f0h, fah, 02h, 00h. The last "00" indicate Fin Low was used.

    Sensitivity of input signal
    Below you will see a diagram of some sensitivity measurement I have made with a Marconi Signal Generator 2019A.
    The input sensitivity of the Transcendent Frequency counter can be found in the graph below.
    The blue line represent the Fin Low and the red line represent Fin High.
    The x-axle show frequency in log and the y-axle show input sensitivity in dBm.
    As you can see, both inputs are very sensitive. You only need to feed the Transcendent with a few mV to get it working.

    Sometimes your RF signal is to strong for the frequency counter and then you can add attenuators between the signal source and the frequency counter.
    An attenuator is an electronic device that reduces the amplitude or power of a signal without appreciably distorting its waveform.
    Attenuation are expressed in decibels of relative power.
    As a rule of thumb 3dB pad halves power, 6dB quarters, 10dB is tenth, 20dB is 100th, 30dB one in one thousand and so on.
    For voltage you double the dBs so for example 6dB is half in voltage.

    Attenuators are very simple to build, and they works really good.
    The picture at right show you how to build a 6dB attenuator.
    You can serial connect several attenuators if you need to.

    6dB means that the output power is only 1/4 of the input power.
    It also means that the output voltage is 1/2 of the input voltage.
    As you see I have used 100 ohm SMD resistor because they are cheap, purely resistive and also accurate.
    Here is a good and simple link for calculate attenuators: Pi & Tee Network Resistive Attenuation Calculator

    External 10 MHz reference system
    There is two versions of this KIT.
  • On-board 13MHz reference

  • External 10 MHz reference

  • Some small modification is needed for the external 10MHz reference.
    The external 10 MHz reference should be feed to pin 9 at PIC16F870.
    Remove (red marked) capacitor C10, crystal X1 and capacitor C9.
    Feed the external 10 MHz signal to pin 9, which you can find at crystal position, see figure below.
    The top pad of capacitor C10 is connected to ground and the bottom pad (is connected to pin 9 of the PIC), which also can be used for external 10 MHz input.

    How to use a 10.000 MHz ± 0.1 ppm TCXO as reference
    Shematic below show how you can connect a 10 MHz TCXO reference oscillator to the Transcendent.
    Vcc (orange) and GND (lightblue) can be found on the PCB as figure above shows.

    Running at +5V
    If you want to run the unit on +5V, you must make a small modification to bypass the voltage regulator V1
    Connect a wire (marked red) from pin 1 to pin 3 of the voltage regulator V1 (see picture below).
    The frequency counter can now be run on +5V only.
    V1 can still be mounted on the circuit board, you do not need to remove it.
    Shortcircuit pin 1 and 3 of regulator V1

    Factory Reset
    If SW1 (J6) is held pushed for 10 seconds during power up, the unit will reload the factory setting for all options and settings.

    Order a KIT
    which will include all parts

    The Transcendent Frequency Counter KIT includes all parts, manual, soldering lead, and wick.

    Order here

    Trouble Shooting section
    If you get a problem with your unit, you might find this section helpful.

  • I get no text on my display!

  • Make sure you have +5V to pin 2 of the LCD and that the background light is working.
    You should now test that the contrast voltage of the LCD is ok.
    The voltage at pin 3 of the LCD should be about 0.50V to 1.5V
    This will give good contrast!
    You should also make sure you have 5, 7, 8, 9, 10 to ground.
    Now, you should test that the data signals is arriving to the LCD.
    Look at the signal of pin 14, 13, 12, 11, 6 and 4 and make sure you measure on the LCD.
    I often use a small speaker or piezo element and listen to the signals.
    You should hear clicking sound or beeping tone…
    If you don't have any data communication to the LCD the problem is with the PIC16F870, next section.
    let's fix this
  • My PIC16F870 is not working!

  • Make sure you have +5V to pin 20 of the PIC.
    You should test that the Reset (pin 1) goes high when power is turned on.
    The oscillator should be running at 13MHz. (Test with oscilloscope or equal equipment)
    Make sure that RA0 (pin 2), RA1 (pin 3) and RA2 (pin 4) is low and goes high when SW1, SW2 and SW3 is pushed.

  • The LCD show only zero so my LMX2322 is not working!

  • Check that the circuit is placed in correct way.
    Check that you do not have any soldering bridges between legs or to ground.

  • My RS232 computer communication is not working!

  • Make sure you that you have a RS232 digital signal out on RC6 (pin 17).
    Transistor Q1 with D1 generate a level shift to +5V and -12V for communication to computer.
    At the collector of Q1 you should have the RS232 signal jumping between -12V and +5V.
    (This will only work when the unit is connected to a computer since the -12V comes from the computer.)
    If you do not have this, make sure you have connected the TX, RX, and ground on the D-sub correct.

    Any com-port program (terminal software) can be used to test that data enters the comport of the computer.

    Final word
    I hope you have enjoyed reading about this frequency counter project.
    Hopefully you have found new inspiration for your own projects.
    The main reason I constructed this counter was my own need of a high quality counter. Beside all that, it looks pretty cool.

    Front side
    Here you have it. Few parts and perfect function.

    Back side
    Here you have it. Few parts and perfect function.

    This link will show a very professional box, made by Leo from The Netherlands. Great work and very nice front!

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    Copyright © Last modified on 3 April 2010.