Seems this is OFF TOPIC, but this is the last one I am
responding to, in this topic. If this topic belongs elsewhere,
please do move this and the other common threads out and
into a new topic! Thanks!
combsbt said:
dant said:
[snip!]
completely enclosing the radiative source and then get a spectrum
analyser with a wide-band detector
[snip!]
FWIW,
Dan
The part that I have
bolded is what concerns me here. I am not aware of a "wide band detector" that would suit this purpose. It seems as though I may have to use a different detection system and apply a fourier transformation on it.
_http://www.physicsforums.com/showthread.php?t=14837
wikipedia said:
When processing signals, such as audio, radio waves, light waves, seismic waves, and even images, Fourier analysis can isolate individual components of a compound waveform, concentrating them for easier detection and/or removal. A large family of signal processing techniques consist of Fourier-transforming a signal, manipulating the Fourier-transformed data in a simple way, and reversing the transformation.
Some examples include:
* Telephone dialing; the touch-tone signals for each telephone key, when pressed, are each a sum of two separate tones (frequencies). Fourier analysis can be used to separate (or analyze) the telephone signal, to reveal the two component tones and therefore which button was pressed.
* Removal of unwanted frequencies from an audio recording (used to eliminate hum from leakage of AC power into the signal, to eliminate the stereo subcarrier from FM radio recordings, or to create karaoke tracks with the vocals removed);
* Noise gating of audio recordings to remove quiet background noise by eliminating Fourier components that do not exceed a preset amplitude;
* Equalization of audio recordings with a series of bandpass filters;
* Digital radio reception with no superheterodyne circuit, as in a modern cell phone or radio scanner;
* Image processing to remove periodic or anisotropic artifacts such as jaggies from interlaced video, stripe artifacts from strip aerial photography, or wave patterns from radio frequency interference in a digital camera;
* Cross correlation of similar images for co-alignment;
* X-ray crystallography to reconstruct a protein's structure from its diffraction pattern;
* Fourier transform ion cyclotron resonance mass spectrometry to determine the mass of ions from the frequency of cyclotron motion in a magnetic field.
This may be slightly more complicated than I initially thought, but I think I could still make it happen.
An oscilloscope measures 1/t and a spectrum analyser measures 1/f,
so in a sense fourier transformation occurs here. There are many kinds
of ways to measure 1/t or 1/f but at least there are commercial solutions
already available for that purpose and the high-end products can be very
expensive where precision is required. The less precision, the less the
cost, of course, but for the average person it is still expensive, imo.
Just make sure you understand the difference between an analog vs
digital analyzer, because the later is based on time-sampling and if there
are signals "popping up" between gaps, it could be missed unless special
hardware detection/trigger devices are used.
Just to be sure that you understand, please review:
_http://en.wikipedia.org/wiki/Spectrum_analyzer
A spectrum analyzer or spectral analyzer is a device used to examine
the spectral composition of some electrical, acoustic, or optical waveform.
It may also measure the power spectrum.
There are analog and digital spectrum analyzers:
* An analog spectrum analyzer uses either a variable band-pass filter whose mid-frequency is automatically tuned (shifted, swept) through the range of frequencies of which the spectrum is to be measured or a superheterodyne receiver where the local oscillator is swept through a range of frequencies.
* A digital spectrum analyzer computes the discrete Fourier transform (DFT), a mathematical process that transforms a waveform into the components of its frequency spectrum.
Some spectrum analyzers (such as "real-time spectrum analyzers") use a hybrid technique where the incoming signal is first down-converted to a lower frequency using superheterodyne techniques and then analyzed using fast fourier transformation (FFT) techniques.
or
_http://www.tutorialsweb.com/rf-measurements/spectrum-analyzer.htm
1. What is a Spectrum Analyzer?
A spectrum analyzer is a wide band, very sensitive receiver. It works on the principle of "super-heterodyne receiver" to convert higher frequencies (normally ranging up to several 10s of GHz) to measurable quantities. The received frequency spectrum is slowly swept through a range of pre-selected frequencies, converting the selected frequency to a measurable DC level (usually logarithmic scale), and displaying the same on a CRT. The CRT displays received signal strength (y-axis) against frequency ( x-axis).
[...]
4. Key Features to Consider When Buying a Spectrum Analyzer:
* Resolution bandwidth
* Frequency range
* Frequency stability
* AC/DC Operation
* Service warranty
Resolution bandwidth: This is an important parameter to consider when buying a Spectrum Analyzer. The sensitivity of the spectrum analyzer is directly dependent on the resolution bandwidth of the analyzer. If your measurements are over a wide band, a 3 KHz RBW is normally sufficient. If you need to make very narrow band measurements (such as filters), then consider a 300Hz or even a 10Hz RBW spectrum analyzer. Obviously, a spectrum analyzer with lower RBW costs more than a spectrum analyzer with 3 KHz RBW.
Frequency range: This is the range of frequencies that you need to make measurements. Spectrum analyzers are available from 100 Hz to 50 GHz range. If you require measurements up to, say IF to 2.4 GHz, a spectrum analyzer from 10MHz-2.4 GHz would be suitable.
Frequency Stability: Frequency stability is the ability of the spectrum analyzer to maintain the frequencies within a specified accuracy. The frequency stability is dependent on the Local Oscillator stability of the spectrum analyzer. For narrow band measurements, this is a very important parameter. Spectrum analyzers do not normally have very high stability clock. If high accuracy of measurement is required, consider buying a spectrum analyzer with provision for external frequency reference. In such an event, the accuracy of the spectrum analyzer is as good as the external reference.
[...]
And then for the equipment: Google: "Wideband detection spectrum analyzer"
...and there are a "ton" of these out there. Seriously, I wonder if your school has
any money to have one of these beasts (they ain't cheap) and if not, then you
have to make do with what you can, if at all. Perhaps you can look into eBay or
Military surplus stores and get lucky, and I wish you the best of luck.