Computer Science Project
The main objective of the NDL project (Noise Data Logger) was “Measure and analyze the noise, using technological means available and without a large investment.” I think that the objective was meted because I have develop cognitive abilities to put in practice the knowledge and skills obtained during the last years and in special this year at Computer Science - UH. As I said the project have a great component of practice and your management was made week by week in the project web page.
The NDL software developed in VB 6.0, to capture and analyse noise will be presented next.
VB program structure, is divide in five parts:
The menu is the interface of NDL system, where we can record, read and analyse data.
This option inform where the ADC-42 is connected, the driver version and number of samples by second collected by the converter.
In this option we can choose the time and steps of recording, show the number between 0 and 4095 (see cap. 6), volt reading, time of recording and save data in a text file.
A list of recorded values can be seen with this option.
The last menu allows make a chart of some of the collected values.
Others type of noise
Analyze radio frequency (RF) noise, is another application of the interface ADC-42. In earth some type of communications use transmitters that work in the range of 100 KHz to 30 MHz (low frequencies to high frequencies). These frequencies are modulated by some signals (voice, fax, rtty, cw, etc). But from space come other signals, these signals are emitted by matter. Matter emits radio frequency (RF) energy dependent on the temperature and makeup of the matter. The analysis of these signals that come from space is Radio Astronomy. Astronomers use light energy, collected by telescopes, to see deep space.
Radio Astronomers use radios and antennas to receive RF emissions and noise from space. What we need to receive and analyze this RF noise? Basically we need:
1. Antenna dipole
The antenna is a wire with a certain length, isolated from earth. The length depends of the frequency that we want receive. If we want receive 20 MHz the antenna must have λ/2. This type of antenna is a dipole and can receive RF signals from two sides. If the wire is in direction N S, receives from E W and vice versa. λ=300/f λ=300/20 λ=15m [300=c if f are in MHz]
2. HF Receiver
A HF receiver normally receive from 100 KHz to 30 MHz with some types of modulation (AM, SSB,FM), there are many models in the specialized market. I use the R70 from Icom is a receiver from the 80’s that we found used on eBay.
3. ADC-42 converter
ADC-42 needs no presentations, as has already been presented above. With the converter we can collect all signals received by antenna and receiver in a log and then study and analyse the collected data. The small voltages produced in the receiver speaker are converted in Bytes by the converter.
4. Computer and Software
The computer and software can analyse the signals (sounds) of the receiver. The analysis will be related to the frequency of the signal, your intensity, and hours of the day with activity. At http://www.dd1us.de/spacesounds%206.html we can see many examples of this application.
JM Freixo Nunes © 2009