Re: [IRCA] SPR4 audio

[Walter Salmaniw <salmaniw@xxxxxxx>]

At 11:38 AM 11/28/2005, you wrote:
>Message: 8
>Date: Mon, 28 Nov 2005 11:18:33 -0800
>From: mwdxer@xxxxxxxxx (Patrick Martin)
>Subject: Re: [IRCA] SPR4 Audio Help
>To: cafe@xxxxxxxxxxxxx, irca@xxxxxxxxxxxxxxxx (Mailing list for the
>        International Radio Club of America)
>
>Colin,
>
>No, the SPR4 is solidstate and nothing was added except a couple
>switches. The 2.3 khz filter was there already for SSB. It came with the
>SPR4 stock in 1971. The change was made to the SSB filter would work in
>the AM mode. That is all. The skirts are very sharp and the splits pop
>out of nowhere. The sellectivity is great. I just want to clean up the
>audio. It works fine in the regular wide (4.8 khz) filter mode and the
>audio is very clear and crisp. It just gets muffled in the 2.3 mode too
>much. 
>
>Thanks.
>
>73,
>
>Patrick


Patrick, isn't this just the result of using too narrow of a filter.  Every receiver I've ever owned (must be 25 or 30 now) have all had muffly audio once you narrow below 4 kHz using AM and 2.8 kHz in SSB.  I rarely use the very narrow filters just for the same reason.  Muffly unintelligible audio.  The best solutions seems to be the use AM synchronous detection when that works, or something like the Sherwood SE-3 and shift the carrier of interest away from the offending splash, but keep the wider bandwidth.  I gather this is a limitation that can't be overcome.  i.e.  you'll never get clear audio using a 500 Hz filter, even though it in theory would be useful in tight situations.  Human speech is between several hundred Hz and about 6000 Hz (the consonants), so it makes sense that too narrow filters simply can't work in processing human speech.  Am I making sense (I'm speaking here as a physician rather than any kind of technical expert!)........Walt Salmaniw, Victoria.



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