Development of a Solar Storm Radio Telescope
2.1 Methodology - Procedure
3.1 Amplifier circuit:
a. Assemble the circuit within the dashed shaped as shown in Figure 3.1.1 on a breadboard.
b. Test the amplifier circuit by feeding a weak sine-wave signal of around 15-20 kHz into the terminal block J1 on breadboard with the signal generator. Connect the oscilloscope probes of Channel 1 to T1 and the oscilloscope probes of Channel 2 to J1. Monitor the output at T1 with an oscilloscope while adjusting the gain with the trimmers R2 and R4 until maximum amplification is gained. Refer to Figure 3.1.2 and 3.1.3
c.Troubleshoot the circuit if needed and then solder permanently on a perfboard.d. For the second half of the circuit, solder d. phono plug to the end of a 1m long coaxial cable. Refer to Figure 3.1.4, 3.1.5 and 3.1.6.
e. Solder T1 and T2 to the coaxial cable as shown in Figure 3.1.7 and 3.1.8.
Figure 3.1.1 - Schematic of amplifier circuit. (Andrews, "How to Build Your Own Radio Telescope", 2007)
Figure Figure 3.1.3. Testing the amplifier circuit)
Figure 3.1.5 The phono plug.
Figure 3.1.4 75 Ohm Coaxial Cable.
Figure Figure 3.1.6 Soldering the cable to the Phono plug..
Figure 3.1.7 Soldering one end of the Audio Isolation Transformer to jumper wires and the other to the coaxial cable..
Figure 3.1.8 Soldering an Audio Isolation Transformer in the middle of the cable..
3.2 Construction of the Antenna:
a. Saw off and keep 0.2m from one end of each of the 1.2m pipes.
b. Construct 2 rectangles using 2 of the 0.95 m pipes and 2 of the 1.0 m pipes each. Use the T-shaped fittings to join the sides.
c. Insert the 0.2m pipes into the left fittings of both rectangles. Add an L-shaped fitting to the 0.2m pipes.
d. Facing the two rectangles parallel to each other, insert the remaining 2 0.95 m pipes to join the two rectangles. The finished structure should have a 0.2m gap between the cuboid and the floor.
e. After ensuring that the structure is steady, use a hot glue gun to glue all the fittings in place. This will make the stronger and less brittle.
f. Stick one end of the speaker cable to the cuboid. Wrap the speaker cable around the cuboid 55 times, preventing any of overlapping of the cables. This will make the counting of the number of loops easier. Refer to figure 3.2.1 and 3.2.2.
Figure 3.2.1 Speaker Cable 12 AWG
Figure 3.2.2 Winding the cable around the antenna structure
3.3 Antenna Tuning:
a. To measure the natural resonance of the antenna, make another single loop of the same wire on the cuboid, parallel to the antenna, at a distance of around 10 cm away. Strip the ends of the loop as well.
b. Connect the oscilloscope probes directly across the open loop terminals of the antenna.
c. Set the signal generator to produce a sine wave at about 140 kHz. Connect the signal generator across the ends of the single loop of wire.
d. Adjust the Volts/Div on the oscilloscope to make sure the wave displayed fits the screen.
e. Measure the voltage induced in antenna at that frequency using the oscilloscope. Record it.
f. Slowly increase the frequency produced. Observe the voltage induced by the antenna on the oscilloscope. After a certain frequency, the voltage induced should begin decreasing.
g. The frequency at which the antenna induced its peak voltage is the natural resonance of the antenna. Record down the frequency.
h. If the natural resonance is higher than the frequency of the chosen VLF station, add the polypropylene capacitors to the antenna, starting with the smallest one.
i. To do this, place the tuning capacitors in parallel on a breadboard. Using jumper wires and crocodile wires, connect the circuit to the open loop terminals of the antenna. Connect the other end of the circuit directly to the oscilloscope. Refer to Figure 3.3.1 and 3.3.2.
g. Stick the other end of the speaker cable to the structure as well.
h. Find a suitable VLF radio transmitter. If the distance between the radio telescope and VLF radio transmitter is lesser than 500 km, the received signal may not show sensitivity to the changes in the ionosphere. However, if the distance is more than 5000 km, the signal transmitted may be to weak to be detect by the radio telescope. Furthermore, the VLF radio transmitter chosen should be as powerful as possible. Thus, the radio telescope will be able to distinguish the signal from background noise easier and it will decrease the impact of local interferences (Andrews, 2007). A list of VLF stations can be found at: http://sidstation.loudet.org/stations-list-en.xhtml.
Figure 3.2.1 Speaker Cable 12 AWG
Figure 3.2.1 Speaker Cable 12 AWG
j. Repeat steps d. to f. to find the resonance of the tuned antenna.
k. Add more capacitors to the tuning circuit and measure the resonance of the antenna until it matches the frequency of the selected VLF (19kHz - Refer to Figure 3.3.3).
l. Another alternative would be to increase the number of turns of the cable until the desired resonance is achieved. The additional wire can either be soldered the original antenna or attached using wire terminal blocks.
Figure 3.2.1 Speaker Cable 12 AWG
3.4 Finishing Construction of the SSRT:
a. Once the antenna has been tuned correctly, wrap the loops in duct tape to keep the loops in place and also to protect the cable from the UV rays of the Sun.
b. Solder the tuning capacitors onto a separate perfboard and solder it directly across the open loop terminals of the antenna.
c. Connect the other end of the tuning capacitors to J1 of the amplifier circuit.
d. If the telescope is being placed in an outdoor area, secure the amplifier circuit into a waterproof box and make sure all exposed wires are waterproofed using silicone sealant.
3.5 Data Collection and Analysis
3.5.1 Spectrum Lab software
On a fully functional Windows computer with an internal PC sound card, install the software ‘Spectrum Lab’. The link to the installation website is <http://www.qsl.net/dl4yhf/spectra1.html#download>. ‘Spectrum Lab’ is a freeware audio analysis package by DL4YHF. It digitizes the signal received at the sound card from the antenna, performs a fast Fourier transform on it, measures the power of the VLF transmission, and outputs time stamped readings to a text file log. It then produces charts of the power against time by reading the log files and graphing them.
3.5.2 Placing of Solar Storm Radio Telescope
The orientation and placement of the antenna will greatly impact signal reception of the antenna. Therefore, the fully constructed solar sunstorm radio telescope should be placed in the direction of the VLF station. This is because the telescope receives signal most strongly in the direction plane of its loop and the weakest reception perpendicular to the signal. Also, to minimize local interference from other signals, it must be placed away from the school’s electrical system. Ideally, metal objects, walls and large number of people, the human body, largely composed of water, absorbs radio frequency energy (Rochman, 2012), should be avoided between the antenna and VLF station.
Hence, the antenna will be placed on the school roof, as far as possible from the school’s electrical wiring. At this location, there will be a minimal number of metal objects, walls and people as compared to lower levels of the school building. Thus, it is essential that the telescope is fully waterproofed and protected from damage by prolonged exposure to the sun. If need be, the antenna can be secured to the ground using duct tape to ensure that it is safe from strong winds.