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

jljarvis jjarvis at keithley.com
Sat Dec 1 15:39:47 EST 2001

Continuing with K1KP's comments, and my own:

With regard to the artifact I described as "agc burble".

I tested another 756pro, with the same conditions, and found
the same results.

That is,  when using a 2.0 KHz filter in SSB, I hear a shadow
signal, from any signal within the upper 15KHz wide IF pipe.

Reproduced as follows:  AGC mid, default timing.  Filter set to
2.0, using filter set menu, not pbt.   Listen on phones with
bass response...Heil proset works fine.  Tune in an s9 or greater
signal, then tune off to a quiet spot within 7.5 KHz of the signal.
You should still hear a low level, low frequency replica of the
signal, which won't 'tune in'.   Once you identify this, then
tune back onto the signal.  Note that the shadow is STILL present.

If you widen the passband to 2.5 or 3.0, the effect is not noticed,
possibly because band noise obscures it.   It's noticeable on cw,
and data, as well, as long as you have the narrower filter selected.

One PRO-II user says he doesn't notice the artifact.

Anyone care to hazard a guess as to the origin of it??

Jim, N2EA
Jim Jarvis
Keithley Instruments
Essex Vermont
802 872 5830 voice
802 872 5831 fax
440 498 2991 paging/messaging

"If the only tool you have is a hammer, you tend to see every problem as a
nail."  Abraham Maslow

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