I have always admired what Don has done with his modulation system. That 3400 hertz brick wall filter is a rarity unless one uses high technology active circuitry such as active op-amps, switched capacitor filters, dsp, etc. I believe Don has a passive module that does a great job. I wonder where he got it? Also consider your individual voice characteristics, microphone, and speech polarity when building a modulation system. Jim WD5JKO
Donald Chester <[EMAIL PROTECTED]> wrote: >What is a good ballpark response that I should use for operating AM in the >amateur bands. > I would shoot for minimum of 100~ to 5000~. According to the UTC catalogue (United Transformer Co.), to keep phase shift distortion to a minimum, the response capability of the transmitter should run one octave above and one octave below the actual response used, so a transmitter with 50~ to 10,000~ capability would sound better even with restricted response of the audio actually used. Of course, that would require broadcast quality components. I would suggest running response tests on the transformers in the rig, and then make sure the coupling components in the rest of the audio chain allow at least the response of the most restricted transformer. If you feel you need to further restrict the response in any way, it should be done right at the microphone preamp. If you limit your overall response to 300-3000~ you might just as well run SSB. I have been able to get satisfactory results with a very sharp, brickwall lowpass audio filter that cuts off at 3400~, in combination with a rising response boost in the mic preamp beginning at 800~ and peaking at about 9 dB from 2000~ to the cutoff frequency of the filter, while the low frequency response remains flat down to about 40~. Don k4kyv ______________________________________________________________ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected]
