Hello all,
I cannot confirm Steve's findings for my brand new FT1000MP.
The difference between main and sub RX is probably due to the
different filtering (2 x 500Hz main, 1 x 500Hz sub rx) and
the fact that the main rx uses triple conversion versus dual
conversion in the sub rx.
73 de Goetz, DJ3IW
email: dj3iw@donau.de
-----Original Message-----
From: Steven J. Franke <sfranke@uiwpls.ece.uiuc.edu>
To: yaesu@contesting.com <yaesu@contesting.com>
Cc: sfranke@uiwpls.ece.uiuc.edu <sfranke@uiwpls.ece.uiuc.edu>
To: <yaesu@contesting.com>
Date: Sunday, December 14, 1997 8:42 PM
Subject: [Yaesu] FT-1000MP: main rx AF hiss
>Hi All,
>Just received a new FT1000MP and immediately noticed
>that the main rx audio (without EDSP) exhibits what seems
>to be an abnormally high level of AF hiss. The sub-
>receiver sounds much better in this respect.
>I have not measured absolute levels, but I would
>estimate that there is a 10dB (or more) difference
>in total AF noise between main and sub-receivers
>(no antenna connected, 500 Hz filters selected,
>CW mode, EDSP off).
>
>This is not just a difference in audio gain
>between the two receivers, as CW/SSB signals
>are at approximately the same level at the
>outputs of both receivers.
>
>The hiss level varies with the RF gain setting,
>so I suspect that it originates in the 455 kHz IF
>stage, after the filters. Turning the EDSP filter
>on removes the out-of-band components of the hiss,
>but I can still hear an extra contribution to the
>in-band noise that is not present on the sub-rx.
>
>The S-meter reading on live signals are identical
>for both receivers, so I don't think that there is
>a problem with RF/IF stage gains.
>
>The overall effect is to make the main rx sound
>deaf compared to the sub-rx, especially on a
>quiet band with narrow filters.
>
>Has anyone else noticed these characteristics?
>
>73, Steve K9AN
>Thanks/73 Steve, K9AN
>
>
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