Re: How much is the IC-7000 going to cost me?
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Hi Ya'akov,
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This phenomenon (actual blow-by caused by inadequate stopband attenuation of the filter, or signal leakage around the filter) cannot occur in a DSP filter system, as the stopband attenuation and comebacks (lobes) are a long way below the 0 dBr passband-centre reference. Have you attempted to measure the blow-by in your 706 by sweeping across the passband with a signal generator and measuring the audio output in the passband and stopband? Cheers for now, 73, Adam VA7OJ/AB4OJ -----Original Message-----
From: Ya`akov N. Miles [mailto:ve7alq@...] Sent: 25 February 2005 12:22 To: ic7000@... Subject: [ic7000] Re: How much is the IC-7000 going to cost me? --- In ic7000@..., "jdow" <jdow@e...> wrote: From: "Adam Farson" <farson@s...>[snip] Filter ringing is probably what he is hearing. The sharper thefilter the more the filter rings. And it will ring to the tune of offfrequency signals as well as on frequency signals.I should like to disagree. Neither of my two filters ring. Signals 5 kHz off frequency sneak past the 500 Hz and the 250 Hz filters in the Icom IC-706mkiiG. I know it is "blow-by" because I hear the signals offset by the correct amount (2.5 kHz to 7.5 kHz) as high pitched (Morse). I can tune in these signals and of course they are _much_ louder inside the filter passband. Signal strengths I am talking about are 40 over S9 within the filter passband and S5 or less when "blowing by" the filter. I trust that this is not going to be an issue with the ic7000 Scanned by WinProxy |
Adam Farson