# How do these cubesats' whip antennas work?

This answer has identified the three 1U cubesats shown in the question, and links to Engineers Rule's Maya-1: The Philippines’ First CubeSat along with the video Animation of MAYA-1, The Philippines' first CubeSat.

click images for larger size

Question: How does this whip antenna design work? What happens when the deployment mechanism activates? What's the final deployed antenna configuration?

Cropped from article:

I think most of this can be seen from the picture:

There are two antennae made of spring(blue) steel, so will automatically return to a straight line once the far end is released -the near end of one is attached to the white block on the right hand side, and the other to the white block on the top left.

The end is glued to an orange piece of string, which passes through a coil near the bottom of the picture. That coil presumably gets heated up enough to melt through the string (presumably it is nylon or similar) cutting it and releasing the tension that holds the antenna in place.

• A picture of it deployed would greatly aid this description- but I understand the point it made. Hard to visualize what itd look like though. – Magic Octopus Urn Aug 7 '19 at 14:26
• A deployed picture is in my answer. – Camille Goudeseune Aug 7 '19 at 16:21
• That's an ingenious mechanism. – Organic Marble Aug 14 '19 at 9:46

This photo confirms @MikeBrockington's answers: dual antennas, nested when stowed, opposed when deployed.

A later photo at https://www.up.edu.ph/index.php/with-maya-1-flying-high-dost-up-aim-to-train-more-satellite-builders/ shows that the antennas are about 20 cm long. But a poster in the background of that photo shows another cubesat mock-up with different lengths. Also, 20 cm doesn't match the half- or quarter-wavelength of their frequency:

All three CubeSats carry same UHF transceiver which is designed to transmit CW Beacon Signal @ 437.375 MHz

• The mockup antenna seems to have a different material and also to be thicker, so I wouldn't conclude too much about those lengths. However, to get to 437.375 MHz they'd have to be 17 cm each, considerably shorter than I thought to observe from the image. – Ludo Aug 7 '19 at 19:32
• In the image in the question, it looks like the antennas are packaged in blue protective foil. I think this image shows the same antennas without that foil. – Hobbes Aug 8 '19 at 9:15
• It's hard to see, but it seems thinner in the actual thing. Also different screws and a metallic part near the white blocks that I'm not seeing in this mockup. – Ludo Aug 8 '19 at 18:54
• Slightly offended by you categorising my answer as "guesses" ... – Mike Brockington Aug 14 '19 at 15:58

In addition to the answer of Mike Brockington that explains how the deployment (likely) works, I'll add this:

Note that there are two antennas, wrapped into each other in a circular fashion. Each one is connected to the white blocks on the left and right sides. A 1U cube sat is 10 cm in all dimensions and the antennas seem to be wrapped about one and a third of a circle fitting just inside the 10x10 face plate. Assuming that the circle is 7 cm in diameter (just over a centimeter margin on each side to the edge), that means that each antenna part is $$\frac{4}{3} \cdot \pi \cdot 0.07 = 0.29$$ m or 29 cm long.

If it is a half-wavelength dipole antenna, it means that each part is a quarter wavelength and the total wavelength would be about 1.2 m. This corresponds to $$f = \frac{c}{\lambda} = \frac{3 \cdot 10^8}{1.2} = 250$$ MHz, which is about right for the VHF frequency band commonly used for cubesats.

This means that once extended though the antennas would need to point (more or less) in opposite directions. Looking closely at the white block, you can see one antenna will point upwards and one will point downwards once unwrapped.