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Laboratory for Atmospheric and Space Physics

2: Antenna Construction (PVC Masts)

July 14, 2016

by Lucy Todd, Summer 2016.


The construction team! Left to right: Eddie Nerney, Logan Dougherty, Kaleb Bodisch, and Frederick Thayer

With Juno now in orbit around Jupiter and its scientific instruments being turned back on, I wanted to get the antenna erected and working with the receiver as soon as possible in time for Juno’s next flyby on the 27th of August. Although the likelihood of receiving any radio emissions from Jupiter at this time is fairy low (due to the ‘Jupiter observing season’ being predicted to have ended on the 3rd of June this year) receiving emissions later on during the planned Juno mission will be possible. In this case therefore, it is important to get the completed radio telescope working in time for the next observing season (predicted to start on the 9th of December of this year).

Jupiter Season

Image taken from: Graph shows the start and end of Jupiter’s observing season at 11/11/15 to 06/03/16

Receiver Completion and Tuning

To power the receiver, a 12V battery was used and power adjusted using the power dial. The importance of both the quality of the soldering joints and the correct alignment of components became apparent quite quickly when the power was applied and the LED did not light! When inspected, the soldering joints appeared sufficient with no obvious problems such as ‘cold joints’ or ‘solder bridges’. The problems were found when checking the voltage across the battery and the components between the power input and the LED using a multi-meter: the LED was broken and the integrated circuit IC2 was misaligned.

DSCN03175   DSCN0349

Once these problems were fixed, the circuit functioned correctly and was able to be tuned. Using a ‘tune by ear’ method, the tuning dial was set to 20Hz and inductors L5, L4 and capacitors C2, C6 were adjusted until the loudest possible tone could be heard through the loud speakers when they were conncted via the audio 1 output on the receiver. The final top panel was then put in place and receiver completed!

Preparing Dipoles

PVC masts were chosen over metal masts as the risk of unwanted conductivity from using metal was considered too great. Whereas metal masts would have been more rigid and sturdy, the PVC masts are much more susceptible to distortion and so bend very easily, especially when approaching 20ft in height. This lead to a few difficulties during construction therefore and will likely become an issue when attempting to gather data. They are however much more lightweight and cheaper to purchase than the metal would have been.

Before constructing the masts, I first made the dipoles and prepared the coaxial cable ends (see images below).

Each dipole was constructed out of two 12ft (3.66m) copper wires, 3 inductors (pictured above), one 32.31ft (9.85m) RG-59/U coaxial cable and two lengths of nylon rope at 2ft (0.61m) each. The length (λcable) of the coaxial cable is important, as it is related to the operating center frequency of 20.1MHz of the JOVE receiver. It is derived from:

λcable = Vf x λfree space

where Vf is the velocity factor (0.66) of the coaxial cable and λfree space is 14.925m (speed of light ‘c’ divided by the center frequency).

Once all these lengths of wire, rope and cable were cut (requires a long corridor!) I prepared the ends of the coaxial cable by stripping away the insulation as shown above. The coaxial end attached beneath the middle insulator had both the twisted copper strands and central conductor wire soldered in place so as to ensure a strong connection. For the coaxial ends that feed into the JOVE receiver, the F-type connectors were screwed over the top of the unwravelled copper strands with the central conductor allowed to extend out the end.

Antenna Construction


This part required quite a bit more help! Manhandling and drilling 20ft long, bendy PVC is an almost impossible task to do alone.

By Friday 8th of July, the antenna masts were erected! However, due to the dry nature of the antenna site we had chosen and the high winds over the following weekend, one of the mast pairs fell down. We therefore decided to use sandbags around the base and more guylines for extra support.


Now to start the testing and data gathering!

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