Jerry Volpe (KG6TT) said:
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"We discussed the A-D converters in the Orion and that it was their practical
sampling limit.... or max range of ability.... that made it important to keep
the Preamp IN. The object there is to make sure that there is sufficient signal
available to the A-D converters so that the conversion produced a better
sampling overall (think of early audio CDs). If the RF energy applied to the
A-D converters is too weak then the conversion process generates too few
samplings... resulting in continual sampling errors which many of us experience
as 'distorted' weak signal audio (I certainly had)."
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I continue to return to the V1 firmware for my Orion for a number of causes -
always
hoping that a new release of V2 will be as good as the V1 firmware. And, I
certainly have no
reason to doubt what Jerry heard from one of the Ten-Tec engineers about the
A/D converter issue with the V2 code for the Orion and the Orion II. To look
for that issue
in the V1 code, I ran some basic "minimum discernable signal" tests tonight -
similar
to those run by the ARRL for their test reports. I started with a calibrated
signal generator,
on 20 meters, and use a calibrated attenuator pad to further reduce the signal.
I used
Spectrum Lab software, and most importantly my ear, to find the "minimum
discernable
signal" and listened carefully to thee beat note from the signal generator
through the Orion.
With the preamp off I got to a -121dbm signal that I judged to be the "minimum
discernable signal"
from the ARRL procedures - that is about .224 microvolts for those that think
better in those
terms. The RF gain of the Orion was set to 86. The note from the generator was
clear and undistorted.
I then turned on the Orion preamp and inserted additional attenuation looking
for the
minimum discernable signal. With the preamp on I got to a signal of -133dbm - or
about .047 microvolts. The Orion RF gain was set to 80. The note from the
generator
was clear and undistorted.
So I think it is safe to say that the V1 code doesn't appear to have any
issues with A/D
errors at the level of signals that we use in communications through the Orion.
Of course
the noise level on all but the highest HF bands is much above the levels of
these - and the
ARRL's - tests. So, the signal levels passing through the Orion are
significantly above the
test levels.
-----I stopped writing for a couple of minutes to work EL2DX on 160M - My QTH,
the radio
black hole of urban St. Louis Missouri ----- :-)
As I just worked the EL2 on 160M, my preamp was off, my RF gain was on 78, my
AGC
threshold was on .37 microvolts, AGC Decay was at 45dB/S and my hang was set to
.04. You could not ask for a cleaner signal to work - all be it close to the
noise here in
Missouri!
Maybe we will hear more from Ten-Tec about this A/D converter error with the V2
code and the "AGC overshoot." And maybe even get a new V2 code release for the
Orion and Orion II with some more of the issues resolved!
73, Merle - W0EWM
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