Function Generators typically produce Sine, Square, Triangle, Saw Tooth and DC signals. Many modern instruments include an AWG or Arbitrary Waveform Generator signal as an additional selection. This allows you to construct your own custom waveform to meet your testing needs. Typical examples might be a dual/multi tone audio signal to test intermodulation distortion in an audio amplifier or a complex modulated signal to test an RF demodulator.
Fig 1 HP Laptop & PicoScope 3205 Scope/Spec/FGn
In order to use the AWG, you have to create your waveform using a special editor or a math program. Essentially your are creating the digital samples that paint the actual waveform that you want. The quality of the waveform is limited by the hardware sample limitation of the instrument.
Fig 2 AWG Editor
The AWG editor allows you to customize various waveforms, draw them, record them from a scope and modify them, or import CSV text files from a math program that was used to construct them. A CSV file is a text file consisting of a series of floating point numbers separated by commas, representing the signal sample values taken at a particular sampling rate Fs and lying between a minimum voltage of -1.0V and +1.0V.
Figure 3 shows a Scilab program to generate a waveform consisting of two sine waves at 400Hz, 1KHz and with Fs sampling frequency 44.10KHz. The resulting samples are written to a column using the function csvWrite. The common period for 400Hz = 2.5msec & 1000Hz = 1msec, is 5msec. Samples are collected for this period. Then the CSV file is read into the AWG, and the samples are written and repeated every 5msec or 200Hz. Figure 4 shows the AWG output taken over 2 periods or 10msecs. Figure 5 shows the AWG output spectrum clearly showing the two tones of 400Hz and 1KHz.
Just saw Alex Holmes’ s documentary “Maiden” at the Toronto International Film Festival. It’s about Tracy Edwards all female crew that sailed around the world in the Whtibread 1989 race. It follows Tracy’s early life and the various steps leading up to the race. An incredible study of courage, persistence and bravery in the face of incredible opposition, problems and of course mother nature. Any one interested in sailing or adventure this is for you. A testament to the optimism of youth.
On March 31st 1931, Sir Francis Chichester left the Northern Tip of New Zealand on an East to West flight across the Tasman sea. He stopped to refuel at Norfolk Island and Lord Howe Island. Let’s determine the great circle distance and bearings that his Gypsy Moth float plane Madam Elijah ZK-AKK had to fly between these two points using the Spherical Haversine law.
The great circle distance using the Spherical Haversine law is:
GCD = 895.3Km (483.4Nmiles), Bearing of Lord Howe Island = 249.9deg. This agrees with the Google Earth plot.
For some time I have wanted to see how many television channels I could receive from the CN Tower in Toronto. I can clearly see the TV antenna at the top of the tower from my apartment balcony, although it is boxed in on both sides by buildings. The 7.6Km Google Earth path is shown below.
I used a simple Yagi antenna and mounted it on a wooden dowel combination to easily allow it be rotated and temporarily but securely attached to the apartment balcony railing.
I placed my TV in scan mode to see what it would pickup. I was amazed to find that I detected 24 channels listed in the spread sheet below:
I also scanned from 400MHz to 800MHz with my spectrum analyzer to see what I would detect:
A close up on the strongest signal at 536.3MHz shows the following spectrum with carrier level at -60dBm and spectrum at -73dBm:
A simple RTL-SDR receiver can be used to receive marine weather forecasts. The unit is small and inexpensive (approx. $25). It can be controlled by using the software program SDR# or other similar programs. The picture above shows my unit plugged into the usb port on the left side of my laptop, the display shows Weather Radio Canada station XMJ-225 on 162.4MHz. The picture below show a simple whip antenna on my apartment balcony.
“I must go down to the seas again, to the lonely sea and the sky, And all I ask is a tall ship and a star to steer her by;” from Sea Fever by John Masefield
Currently I am calibrating my 3 sextants from several known locations in Toronto. One requires a water horizon and the other 2 have bubble horizons. Trillium Park is gorgeous, it’s like looking out over the Pacific ocean! I am also reading Ian Strathcarron’s biography of Sir Francis Chichester “Never Fear”. I love Chichester’s cure for mental & physical scurvy: Scotch Whiskey + Lemon!!