At 11:12 AM 04/18/2003 -0500, Jerry wrote:
> Hence the
>classical filter rigs, the Collins KWS1/75A4 and S-line use 2.1 KHz
>filter bandwidth and set the carrier 300 Hz from the passband corner. As
>do Ma Bell's frequency multiplexed wire and microwave voice circuits
>since the 30s when frequency multiplex was developed.
Having had the Collins pair you speak of, I can attest they both used 3.1
filters, not 2.1. This was the reason I received so many "good quality"
reports up into the late 80's, when the typical transceivers had 2.1 or 2.4.
Also, having been in the Telecom business for the last 40 years, I can
also say that the typical freq division mux (ssb) systems allowed an audio
bandpass of 3 khz.... (300 to 3300 Hz) The channel width was 4 kHz
with a "guard band" of 1 kHz. The only restrictions to the high end
audio in telephone carriers systems was the 2600 Hz notch filter provided
in some telephone circuit modems to eliminate hearing the "signalling" tone
used for "on-hook/off hook" functions.
You're overview was interesting, and always appreciated.