Development of a Solar Storm Radio Telescope
2. 3 Methodology - Troubleshooting
Throughout the project, the SSRT required much troubleshooting when the expected results were not obtained. It taught us a lot in areas that we were almost entirely new to and we have gained invaluable experiences from it.
1. Breadboard testing-
The amplifier circuit was built onto a breadboard first. Initially, we achieved the amplification we had wanted however, after about a day, it did not amplify the input into it well as seen in Fig 2.1.1. The circuit was rebuilt a second time to ensure there were no misconnections and more research was done to find the problem.
Figure 2.1.1 shows the improper amplification on a breadboard
Solution: The poor amplification was due to the breadboard’s own internal capacitance. For this reason, circuits that revolve around radio waves should not be built on breadboards. Following this, the amplifier circuit was soldered directly onto a perfboard, to eradicate this issue completely.
2. Perfboard testing-
On the perfboard, initially, the circuit was not functioning very well at all. Being the first time we had soldered a complete circuit onto a perfboard, we hypothesized that this may be due to poor connections.
Solution: Using the continuity function on a digital multimeter, we tested each solder point on the underside of the perfboard to ensure that the components were all connected as they should be. Some dubious connections were resoldered and certain positions had to be changed. This had to be done very carefully as the holes on a perfboard are in very close proximity to each other so, we gathered more knowledge on the appropriate procedures of soldering via the internet and experienced teachers and lab staff.
After that, we achieved a good amplification of the input signal. However, the issue was that sine waves were clipping and unclipping continuously as seen in Fig. 2.2.1
Figure 2.2.1 shows the clipped amplification from the perfboard
Solution: Clipping is a form of distortion that occurs when too much current is passing through the circuit. Hence, the amplifier will only be able ‘scale’ up the input sine wave to its threshold voltage before limiting, or cutting, off the rest. In our case, this meant that the resistors were not functioning in the circuit.
The resistance of the two trimmers was tested using a digital multimeter and when it was discovered that one of the trimmers was malfunctioning and did not even affect the amplified signal in any way, we swapped both trimmers for better quality ones to be sure.
Another minor issue was with a regular resistor. This particular resistor had a little paint coating on its wires as well. When it was soldered, the exposed wire was cut short to facilitate the soldering, leaving only the painted wire behind. The solder hence, was only on the insulating paint and did not complete the connection between the resistor and the next component.
Solution: The paint was scraped off with a filer and the resistor resoldered. Finally, through this process, the expected amplification was achieved as seen in Fig. 2.2.2
Figure 2.2.2 shows the desired amplification on the perfboard
3. Spectrum Lab
Initially, Spectrum Lab was unable to recognize the signal being sent through the soundcard at all. The input monitor displayed only a flat green line and the spectrogram’s waterfall display showed absolutely nothing. We were very new to this software and had to scrutinize the programme for a possible problem quite lengthily.
Solution: As we sought the issue, we realized that with the zip file of Spectrum Lab that was downloaded from an open-source package, two files of the application were encompassed. Both were of different formats and only the second file was compatible with our computer. It worked perfectly, displaying the desired signals. This was a key achievement for us as we now had a working antenna, amplifier circuit and software.
4. Intensification of frequency
Within Spectrum Lab, the spectogram’s waterfall display was only showed a slight intensification of the 19kHz frequency it received as seen in Fig 2.4.1. Through the soundcard, Spectrum Lab receives signals of various frequencies and analyses their strength to intensify the colour on the spectrogram proportional to the power. This meant that contrary to the expectation, the software was not receiving an amplified signal of 19kHz from the antenna and amplifier circuit.
Figure 2.4.1 shows the slight intensification on Spectrum Lab
Solution: We knew that the amplifier circuit and antenna were working through the testing with an oscilloscope prior to connecting it to the computer. Hence, we were able to narrow down and deduce the source of the issue to be either the soundcard of the coaxial cable. USB soundcards, like the one we were using, are generally mass produced and because of its value, is cheaply reproduced and sold. Thus, it is very common to buy a counterfeit soundcard of low quality. After replacing the soundcard, a very strong intensification of the 19kHz - 20kHz frequency range was obtained as seen in Fig 2.4.2
Figure 2.4.2 shows the desired strong intensification on Spectrum Lab