This is great stuff. I am not too surprised to see that adding in the RF
gain produced a 10 db (actually a little more) improvement in the minimum
discernable signal. That is what one would hope for.
Of course you are right in that most actual signals (and noise) will be well
above that point, making it essentially moot.
Now, one other point is that if the limits of the A/D converter performance
noted by Jerry are inherent to the converter black box itself, then V1 vs.
V2 code should have nothing at all to do with it.
It is not obvious to me from this information if that is the case or not.
73 de Gary, AA2IZ
----- Original Message -----
From: "Merle Bone" <merlebone@charter.net>
To: <tentec@contesting.com>
Sent: Friday, February 01, 2008 9:26 PM
Subject: Re: [TenTec] ORION II CW pile up readability
> Jerry Volpe (KG6TT) said:
> --------------------------------------------------------------------------
-------------------------------------------------------
> "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)."
> --------------------------------------------------------------------------
----------------------------------
>
> 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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> TenTec@contesting.com
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>
>
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