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-
- The SINE/SQUARE Wave Generator.
- -------------------------------
-
- Technical specifications:-
- --------------------------
-
- Designed frequency range.............. 25Hz to 2.5KHz.
- Usable range.......................... 10Hz to 3KHz.
- Frequency accuracy.................... + or - 2%.
- Output voltage........................ 1280mV Peak to Peak, - 20%.
- Output impedance...................... 47 KilOhms.
- Output voltage range.................. 0 to maximum level, 20mV steps.
- Sine wave distortion.................. 5% or less.
- Square wave rise time................. 10 microseconds or better.
- Hum and Noise......................... -30dB below fundamental signal.
-
- Note:-
- ------
-
- These specifications apply to a standard A1200 ONLY at 1KHZ, and may NOT
- be exactly the same for an A500, A500+, A600 etc, etc.
-
- ----------------------------------------------------------------------------
-
- Keyboard controls:-
- -------------------
-
- The keyboard controls are shown in brackets, for example (q), (Q).
- IF the letter is a capital, then press one of the ~SHIFT~ keys whilst
- pressing the required letter.
-
- (i) This will increase the frequency at the rate of 50Hz per stop.
- (I) This will increase the frequency at the rate of 1Hz per stop.
- (d) This will decrease the frequency at the rate of 50Hz per stop.
- (D) This will decrease the frequency at the rate of 1Hz per stop.
- (o) This will increase the output voltage.
- (O) This will decrease the output voltage.
- (s) This will switch the mode to SINE.
- (S) This will switch the mode to SQUARE.
- (q) or (Q) will exit the program.
-
- The mouse can be used to Quit or move to the background. This is not
- needed for correct operation of the software and can be disconnected
- if running the software from a CLI or SHELL window.
-
- ----------------------------------------------------------------------------
-
- Limitations of the computer:-
- -----------------------------
-
- The specifications of this generator are poor compared to a professional
- piece of test gear, this is due to the AMIGA's hardware. However I have
- worked around these limitations to a great extent to get the most out of
- the audio hardware. The two main limitations to consider are ALIASING and
- audio amplifier BANDWIDTH. Although it was possible to generate a low
- level SINE wave to approximately 10KHz it was suffering badly with these
- two constraints. The audio amplifier's BANDWIDTH is approximately 7KHz.
-
- ALIASING is the effect of sum and difference frequencies generated by the
- hardware between the sampled waveform and sampling frequency. To reduce
- this problem the sampled waveform must be sampled at more than twice the
- frequency of the waveform itself plus 7KHz for the AMIGA's audio bandwidth.
-
- For example:-
- -------------
-
- Sampled frequency = 1Khz.
- Sampling frequency = 7Khz.
- Sum of the two frequencies = 7+1 = 8KHz.
- Difference of the two frequencies = 7-1 = 6KHz.
-
- The 8Khz frequency is outside of the audio amplifier's bandwidth and so
- will not be passed through.
- However the 6Khz frequency will pass through as it is inside the audio
- amplifier's bandwidth.
- So to eliminate both we must add 7KHz to the sampling frequency, which
- means that the new sampling rate to produce a ~CLEAN~ waveform would be
- 7+7 = 14KHz. Now both the sum and the difference frequencies are out of
- the audio bandwidth.
-
- BANDWIDTH is the highest frequency that can be passed by the amplifier.
- Thus the effect of the filtering required to try to reduce the ALIASING
- errors effectively reduces the output of the higher frequencies.
- Once lost these high frequency components cannot be retreived.
-
- Because this program was written with both NTSC and PAL systems in mind
- the frequency generated is a compromise between both. So therefore the
- accuracy is not quite as good as it could be. However this should not be
- a problem.
-
- ----------------------------------------------------------------------------
-
- Construction of the test lead.
- ------------------------------
-
- Parts required:-
- ----------------
-
- 1) A length of coaxial cable approximately 1.5 metres, RG58 or UR76.
- 2) A PHONO or RCA plug.
- 3) A countersunk head brass screw approximately 1.5" (37mm) long.
- 4) A matching nut.
- 5) An insulated crocodile clip.
- 6) A length of sleeving, (the sleeving off of the coaxial cable will do).
- 7) An old ballpoint pen case.
-
- ----------------------------------------------------------------------------
-
- Tools required:-
- ----------------
-
- 1) Soldering iron.
- 2) Solder.
- 3) Side cutters.
- 4) Pliers.
- 5) File.
- 6) A hobby saw.
- 7) PVC tape.
- 8) Superglue, (be very careful with this).
-
- ----------------------------------------------------------------------------
-
- Strip at least 6" to 9" of sleeving off of one end of the coaxial cable.
- Do NOT discard this sleeving. Seperate the braid from the inner conductor.
- Solder the inner conductor to the head of the brass countersunk-head screw.
- Double click on the icon ~HardWare~ for additional information. To quit
- the ~HardWare~ screen press any key and the screen will close.
- Place the sleeving over the braiding before fitting the crocodile clip
- and then wrap some PVC tape around the ~Y~ joint of the cable. Solder
- the crocodile clip to the braiding. Dismantle an old ballpoint pen to
- obtain the case. Discard all of the inner parts of the pen.
- Before reassembling the screw into the ballpoint pen case, cut the case
- down to a practical length (approximately 3" to 4"). Fit the PHONO (RCA)
- plug to the other end of the coaxial cable, inner conductor to the pin,
- the braid to the outer part of the plug.
-
- When you have checked this cable and are confident it is electrically good
- use the superglue to seal the top of the pen case and the nut. Do NOT get
- this glue on you or anything else as it is dangerous. Allow time to dry.
-
- ----------------------------------------------------------------------------
-
- Starting the Audio Generator:-
- ------------------------------
-
- *** WARNING ***
-
- DO NOT USE WITH VOLTAGES GREATER THAN 12 VOLTS D.C.
-
- 1) Ensure the AMIGA is switched OFF.
- 2) Connect the cable to LEFT channel phono socket.
- 3) Connect a blank PHONO/RCA plug to the RIGHT channel phono socket.
- 4) Switch on the AMIGA.
- 5) Start the ~Sin_Square_Gen~ software from its icon.
- 6) Connect up to an audio circuit and start testing.
- 7) When finished switch OFF the AMIGA and disconnect all of the hardware.
-
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-