[CQ-Contest] 756Pro: definition of 'ratty'

Barockteer at aol.com Barockteer at aol.com
Mon Nov 26 11:30:01 EST 2001

I've had several offline replies to my query about 'ratty' CW audio on
the 756Pro, so I thought I would be a bit more specific as to what I

The 756Pro has three characteristics in CW which I find annoying, but
are somewhat subtle, and often go unnoticed by less discerning
users. These are worst with signals over s9. They are:

1. AGC pops. Using fast AGC on CW, the leading edge of words (not
characters) is accompanied by a nasty pop, somewhat like a direct
conversion receiver. Sounds like clipping occuring as the AGC is late
to catch up with a big signal.

2. Flutey sound on leading edges. This is a fifth-order harmonic
distortion of the audio, noticed only when using AGC, on the leading
elements of characters. Noticed more as CW pitch is set lower, or
adjusted. NR can be used to reduce this somewhat, although sometimes
the NR gets itself 'off in the weeds', and actually makes this much
worse. This is not noticeable with manual AGC, or with steady state

3. Key clicks. When using the 'BPF' filter type which has steep cutoff
slopes, there are apparently more keyclicks. These are actually
present withing the passband, and are real signals transmitted by the
sending station. Using the non'BPF' settings, and narrowing to the
same bandwidth, gives softer filter slopes, resulting in less
noticeable keyclicks, albeit at the cost of hearing more adjacent
signals on the skirts.

As I said, these are pretty subtle effects, but you can notice them if
you A/B the Pro against a good crystal filter rig, like 765/781/1000D

I'm wondering how much of this has been cleaned up in the Pro II, as
this could be the basis for upgrading from Pro to Pro II.


Tony, K1KP

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