Jim Reid wrote:
> Sinisa wrote, in part:
> > Connecting and disconnecting your antenna should result
> > in noise level difference of 10-12 dB (~2 S units).
> Since the AGC within the Orion CANNOT be completely
> turned OFF, where should the Threshold be set when
> the above test is performed: high or very low?? Selecting
> the AGC OFF with the Orion results in a default AGC
> Threshold of 0.37 uV, the lowest available setting.
If the external noise moves the S meter sufficiently,
one can use its indication which is reasonably accurate
and does not depend on AGC THRESHOLD.
If the test must be done by external instrumantation or by ear,
AGC THRESHOLD must be increased slightly above the point where the
external noise volume starts to decrease. This ensures that
AGC will stay inactive, and what is heard will reflects actual
power ratios. Exact point is not critical and may be
much higher than the minimum one. Of course, the selected
setting must not be changed during the test.
> > Start with full sensitivity and reduce it until the above
> > condition is satisfied.
> With the AGC threshold sitting high or low?
Orion's AGC works much further from receiver input
than in most other receivers, so AGC THRESHOLD doesn't
influence signal to noise ratio significantly,
although it does influence the perceived volume.
73,
Sinisa YT1NT, VA3TTN
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