Don't jump to conclusions. It may not be your filter. It maybe your audio stages. Typically, amp bandwidth is specified at the -3 dB points. If you have a preamp and one audio stage, then tones at the extremes, say 300 and 3000 would be 3 dB down from one at the center of the passband in EACH AMPLIFIER. The result is that tones at the extremes would be a total of 6 dB down from the center. This is even before any filter losses are factored in. This is why many transmitters let you input digital audio signals later in the chain, to bypass significant losses. And all this is predicated on the assumption that Alinco designed the audio amps correctly and/or that age has not significantly affected the operation. Think about it, you reduce your power to 20 watts to eliminate IMD, and then your transmitted power is reduced even further (5 to 10 watts or even less) for tones away from the center of the passband! A lot of the prior discussions centered around high noise/low signal work. You may have a signal that is entirely copyable when using a few tones centered in the passband, yet have tones that are below the noise at the extremes when using wide modes with multiple tones. Adaption has been mentioned, but the best place is at the transmitter in these cases, since signals in the noise are lost. Whether you like the ESSBers or not, they do understand the ways to get flat audio through their systems. Jim WA0LYK --- In [email protected], "Brett Owen Rees VK2TMG " <[EMAIL PROTECTED]> wrote: > > I have noticed that my tx power varies depending upon where I am in the > passband. > As my radio most likely uses the same crystal filter for tx ssb generation > as it does for RX filtering > then one can in a way map the response of the filter. My radio is an Alinco > DX-77, and I get maximum > output at about 1800 Hz. Having mapped my filter on TX, I suspect that my > filter response is not the steep > sided flat-topped filter response as described in books, but rather is more > of a bell shape. > > Has anyone else noticed a variation in power output across the waterfall? > > 73 de Brett > > -- > =============== > Brett Rees VK2TMG > http://lisp.homeunix.net > > > [Non-text portions of this message have been removed] >
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