Welcome to the EclipseMob team! The antenna you are about to build is a simple loop antenna made of wire. It captures radio signals from the air and feeds them into the receiver.
If you are interested in learning more about the antenna and how it works, take a look at some of the articles in the Learn category, or sign up for one of our Webinars! If you have any questions or want to show everyone how your receiver turned out, create an account on our forum and share them with us.
For help building the receiver, see the "Receiver Instructions" article.
The receiver and antenna are based on a design by Tom Hagen, NE9Y.1
Bill of Materials: The components and equipment you will need to build the antenna. If you received parts from the EclipseMob team, the wire, winding form, and cord hooks will be included in your kit - you can use the bin your parts came in as the winding form. You will need about 30 minutes to complete the receiver. We recommend getting a friend to help!
|28 AWG Magnet Wire||~ 800 - 1000 ft|
|Antenna Winding Form||~ 10 - 12" square|
|Sandpaper (fine grit)||1 sheet|
The sandpaper is used to strip the enamel from the magnet wire. You can also use an Exacto knife or a blob of solder, but in our experience sandpaper works best.
The antenna components included in the EclipseMob parts kit.
Step One: Place the Cord Hooks
Find the side of the box with the two metal snaps and place two of the sticky cord hook backings there.
We recommend placing one of these near the bottom of the box, and one just below the metal snaps. Place the plastic cord hooks on the backings. Repeat the same process on the other three sides of the box, making sure the cord hooks are aligned - the hooks should be the same distance from the bottom of the box on all sides.
NOTE: Some receiver kits include a clear box with an attached lid (not the opaque box shown in these photos). If you have the clear box with an attached lid, the cord hook adhesive will not stick to the box. One option is to try wiping the box surface with alcohol before attaching the hooks. If the alcohol doesn’t solve the problem, we recommend that you use a hot glue gun to attach the hooks to the box.
Step Two: Getting Ready to Wind the Antenna
Winding the antenna loops is not hard, but does take some time and patience. We recommend getting a friend to help count the loops.
Start by setting up the spool of wire. Place the pen (or a similar round cylindrical object) through the spool, and place the spool and pen between the two textbooks. This locks in the spool in place and makes the winding process much easier.
Unwind about three feet of wire from the spool, then wrap a single loop of wire around one of the cord hooks on the bin. Push this loop towards the center of the box. The extra length of wire will be used to connect the antenna to the receiver, so make sure you leave enough length to make the connection. Make sure that all of the cord hooks are open before moving on to the next step.
Step Three: Wind the First 100 Loops
Begin winding the antenna. If you set the spool up as demonstrated above, you should be able to rotate the winding form and guide the wire through each hook as it comes off the spool. Make sure to keep the wire taut as you wind, and try to keep the wire from spreading out too much as you go. If you have a friend helping, have them record each loop as you wind it.
After you have completed 100 loops, place another wrap of wire around the same hook you started on. Leave another three feet of wire, and cut the wire from the spool. Close the cord hooks, tuck the loose ends of wire inside the box, and secure them with a strip of tape.
Step Four: Wind the Second Set of 100 Loops
Repeat steps two and three above for the second set of loops.
Step Five: Strip the Wire Ends
Now that the antenna is wound, the enamel at the ends of the wires must be stripped. We recommend using a sheet of fine grit sandpaper to remove the enamel from the last inch of the wire. When you are finished, you should be able to see the copper underneath the enamel. The left wire in the photo below is still enameled, while the right wire has had the enamel removed.
If you have access to a Digital Multi-Meter (DMM), you can verify that the wire ends havebeen properly prepared by checking the continuity or resistance of each 100 turn loop of wire. You can expect a resistance reading of approximately 20 Ω for a properly stripped wire of this length. After connecting the two coils in series as shown in step 6 the total resistance will be the sum of the resistance of the two 100 turn loops individually
Step Six: Connect the Two Loops
Find the two central free-running ends of each loop of wire and connect the ends together as shown in the diagram. If you have access to a soldering iron, you can solder them together for a better electrical connection.
Congratulations! Your antenna is now complete. Take a look at our other articles if you need help building the receiver circuit or setting up the antenna and receiver system.
 Hagen, Tom. "A Portable, Calibrated VLF Field Strength Measurement Receiver and Loop Antenna." Society of Amateur Radio Astronomers Association West Conference, 2015.