If you received one of our first batch of kits, you should receive an envelope in the mail shortly with the parts you need to upgrade to the new version.


Welcome to the EclipseMob team! The circuit you are about to build is a simple radio receiver. It requires no prior experience or knowledge of electronics, and can be put together on a small solderless breadboard. Just follow the pictures and diagrams below, and in about an hour, you will have built a complete and functioning radio receiver! This receiver and antenna are based on a design by Tom Hagen, NE9Y.1


If you are interested in learning more about electronics or how the receiver works, check out some of the articles under the Learn category. If you have a question about the assembly process, or want to show us some pictures of your completed receiver, create an account on our forum and share them with us.


For help building an antenna, please see the "Antenna Instructions" article.


Getting Started

We recommend that you read through the entire set of instructions before beginning.

Bill of Materials: These are the components and tools you will need to build the receiver circuit. Most of them are included in the EclipseMob Receiver Kit. Parts and tools that you will need to acquire are specified with asterisks (*). Integrated circuit (IC) components have links to their datasheets.

Quantity Component Schematic Reference
  Integrated Circuits  
1 INA 103 instrumentation amplifier INA103/U3
1 LM7812 voltage regulator LM7812/U1
1 LM7912 voltage regulator LM7912/U2
2 AD633 analog multiplier AD633/U5,U6
1 2.2μF tantalum capacitor C3
3 1μF tantalum capacitor C5,C6,C7
1 0.22μF ceramic capacitor C1
6 0.1μF ceramic capacitor C2,C4,C8-C11
1 270pF ceramic capacitor (new part!) C12
1 200 kOhm R2
2 10 kOhm R1,R3
  General Parts  
1 Breadboard  
1 Circuit housing  
2 Switches SW1,SW2
3 25 ft spool of 22AWG (1 each of red, black, blue)  
4 *9V battery*  BT1-BT4
4 9V battery clips  
1 TRRS Cable  CableToPhone
  Tools and Accessories  
1 Velcro Tape  
1 Rubber Grommet  
4 Twist-on Wire Connectors  
1 *Small Phillips head screwdriver*  
1 *Flat head screwdriver*  
1 *Hammer*  
1 *Safety glasses*  

If you have access to a digital multimeter (DMM), tape(electrical or masking), and a small set of pliers, you may find them useful while you build the circuit. If you do not have these tools (especially the DMM), that's ok - they are not required.

Schematic: This shows the electrical connections that are made in the circuit. If you don't know how to read a schematic, don't worry - the step-by-step instructions and photos below will have you building circuits like a pro!

WWVB Receiver V2

Reading the photos: The circuit is built in steps to make the build process easier to follow. There are at least two photos for each step. The first photo indicates where the components and wires should be placed and uses the following conventions:

  • Red X marks and lines indicate where red wires are placed
  • Blue X marks and lines indicate where blue wires are placed
  • Black X marks and lines indicate where black wires are placed
  • Black X marks and Labels indicate where components should be placed. Green lines are used to help clarify any ambiguous placements.
  • OrangeX marks indicate where the positive (+) lead of polarized capacitors should be placed.

The second photo will show what the circuit should look like after the components are placed. You can click on an image to access a higher resolution version of the photo.


Step One: The Positive Power Supply

The first subsection of the circuit that we will build is the positive power supply. It provides +12 V to the circuit and is accessible through the lower red rail on the breadboard.


A Note on Voltage Regulator Integrated Circuits v2 1

                       Note differences in pinout of the two voltage regulators

v2 2 



 v2 3



A Note on Capacitors

Before you place the next components, take a moment to look at one of the tantalum capacitors (C3 - 2.2uF, C5-C7 - 1uF).




These capacitors are polarized, which means they have to be inserted in the circuit in the correct orientation. The positive side of the capacitor is marked with a small "+" symbol, and the lead on this side of the capacitor is usually longer. This side must go to the position marked with an X in the photos.




Step Two: The Negative Power Supply

The negative power supply provides -12 V to the circuit and is accessible through the upper red rail on the breadboard.



v2 4



Step Three: The Amplifier

The amplifier takes the signal from the antenna and increases its amplitude. The INA103 is the largest of the chips included in your EclipseMob Receiver kit.




Make sure that the INA103 is placed in the circuit correctly. The amplifier should be placed so the small dot on its top is on the upper right corner of the chip.

v2 5


v2 6


 More detail on the regulator circuits


v2 7



Detail on the negative regulator L7912 components


v2 8



A  better view of the components around the L7912 negative


v2 9


Step Four: The Multipliers

The incoming signal from the antenna is at a frequency of 60 kHz. This is too high for a cell phone to read correctly. The multipliers are used to convert the antenna's signal into a lower frequency version that a cell phone can read.


The wiring will be placed first, followed by a few resistors and capacitors. The multipliers should be placed so the notch on the chip is facing towards the right.

v2 multiplier 0


The next image shows how to place the wires for the two multipliers.  These wires connect the chips to the positive and negative voltage supplies, connect any inputs we're not using to ground, and help set up the frequency doubler configuration for the multiplier on the right.

v2 multipliers 0p3


Once you've done that, your wires should look like the photo below.  Next you'll place some capacitors and resistors.  These perform a few different functions: the capacitors that connect the positive and negative voltage supplies to ground are there to keep radio-frequency signals off the voltage rails; the two resistors on the left multiplier set the gain on the multiplier output; and the capacitor and resistor on the input of the right multiplier are needed to use it as a frequency doubler.

There are two different resistor sizes used in this circuit: 200 kΩ (R2) and 10 kΩ (R1, R3).  With the V2 parts, we sent you an extra 10k resistor that's not blue, but it will still have a brown stripe first, followed by a black stripe.  You can just move your old resistor, or use the new one if you've already cut/bent the old one into an inconvenient shape.





We'll do this in two steps: first, place everything that isn't a 0.1 uF capacitor.

v2 multipliers 1p1


Next, place four 0.1 uF capacitors:

v2 multipliers 1p2

Finish making the necessary connections between the amplifier and multipliers as shown: from pin 11 on the amplifier to pin 3 on the left multiplier; and from pin 7 on the right multipler to pin 1 on the left multiplier.


v2 10

Note that the leads are shortened and neatly placed. Leaving the original long leads on the parts invites short circuits.

Try to make your board look like the picture when you insert the parts. 



Step Five: Putting It All Together

This step describes the process for connecting the batteries, preparing the circuit housing, and making the final connections to complete the circuit. If you have not built your antenna yet, you will need to build it now - click here for a walkthrough of the antenna winding process.


Prep the Battery Clips

The battery clips you received in the EclipseMob Receiver Kit have plugs on the ends.




Use the wire cutter to remove the plug end and strip approximately a half-inch of insulation from the wires. The wires are twisted strand - if they start to unravel, you can twist them back together with your fingers. Repeat this process for all four battery connectors.




Place the battery connectors in two sets of two connectors each. Take a red wire from one connector and a black wire from the second connector and place them into a blue twist-on wire connector. Twist the wire connector until you feel some light resistance - the wires should now be connected together. Repeat this process for the second set of connectors. Set both pairs of battery clips aside for now. When you are done, the clips should look like this:




Prep the Circuit Housing

Start by placing the conduit box on one of its sides, as shown below. The knockout holes on the conduit box are two different sizes. Make sure that a side with hole sizes "M25/M16" is facing up. Use a flat head screwdriver and hammer to knock out both of the left-hand holes. Wear your safety glasses!




Place the rubber grommet inside the hole you just created. This will secure the TRRS jack and help protect the circuit from the elements.




Remove the yellow piece of paper from the bottom of the breadboard, exposing the adhesive.

breadboard back


sticky side



Place the breadboard inside the conduit box as shown - the fit is tight, but the breadboard will fit. Make sure that the rubber grommet is located in the bottom right hand corner. Cut a piece of velcro that is about the same length as the breadboard. Place the velcro inside the circuit housing and above the breadboard.


Prep the TRRS Jack

Cut three pieces of wire that are approximately 3 inches long. One should be black, and the other two can be any color besides black or red (in most kits, the extra color is blue). Strip the insulation from the end of each wire. Place the wires one at a time into the TRRS jack.  Most smartphones now use the CTIA TRRS standard, so the order of the connections is not the same as is marked on the TRRS jack. You should connect the black wire (for ground) to the second terminal on the TRRS jack, which is marked V.  The two non-black wires should be connected to the first and third terminals (marked with a ground symbol and an R). Use a Phillips head screwdriver to secure each piece of wire in its slot.



Place the TRRS jack through the grommet, and insert the TRRS wires as shown in the diagram below. The diagram also indicates where the final antenna and battery connections will be made. The antenna ground and battery ground will be connected with a twist-on connector, so ANT GND refers to both antenna and battery.




v2 11


This is a completed board ready to install in the plastic box. Battery connection wires are shown.


Run all four of the antenna connections through the grommet. Remember, there should be two loose ends of the antenna, and two ends that are loosely twisted together. The battery connectors should now have four loose ends of wire - a red wire on one end, a black wire on the other, and a red and black wire in the center.




Cut a small length of black wire and strip the insulation from the ends. Place this wire, the two center wires from the battery connectors, and the two center wires from the antenna into a twist-on wire connector, and twist all five together. Be sure your antenna loops are wired as shown in the diagram in Step 6 of the Antenna Instructions. This should be the end result:




Cut two small strips of Velcro and place them on the bottom of the batteries. Splitting them into groups of two makes fitting them inside the conduit box a little easier.




Finally, place the batteries inside the conduit box and make the final battery and antenna connections.

TRRS CTIA completed

Double check all of the connections one last time. When you are confident everything is correct, place the lid on the box. You can leave the lid like this, or use the provided screws to make a secure connection. If you choose to secure the lid, you may want to create an additional knock-out on the front or left of the box to help you manipulate the switches.



Congratulations! The receiver is complete.


Sidenote for any inquiries about the APP and Data Collection

Data is collected through the phone app (available soon) which creates a .wav file and associates it with a time and location stamp. Data is stored through Google cloud services. Users will need to be registered on the eclipsemob site to upload data to the website. The app will check to make sure you are registered. 



[1] Hagen, Tom. "A Portable, Calibrated VLF Field Strength Measurement Receiver and Loop Antenna." Society of Amateur Radio Astronomers Association West Conference, 2015.