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. ============================================================================ Acknowledgements:- ------------------ First of all many thanks to my wife Tricia who allows me to spend many hours on my computers. Also to David Benn and Herbert Breuer for the ACE/AIDE combination supplied on an AMIGA FORMAT floppy disk which made it easy to compile this program. And finally to anyone else who I may have neglected or forgotten. ---------------------------------------------------------------------------- Mr Barry Walker, 70 King George Road, Loughborough, Leicestershire, LE11 2PA, England. Email to:- wisecracker@tesco.net BYE..... ============================================================================