I agree that something else must be going on. Analog meter ballistics might
effect what you see under SSB or CW signals, but I ran my test with a signal
generator using fixed levels and found the discrepancies shown on my website
(http://www.n6aha.com/Orion%20S%20meter%20descrep.htm). The 'easy' fix
would be to make a new meter face, which could be field installed if done
with care. That could also address the Wattmeter problem.
Another interesting discrepancy is that the S reading drops 6 dB when both
receivers are on the same antenna, which makes sense considering the
loading, but there is no compensation in the precision arithmetic when this
occurs. Nor is there for the preamp, which is handled in many radios like
the TS-870 by a menu setting that allows for automatic compensation if you
want it when the preamp is on.
An accurate S-meter may not seem like a big issue, and I have learned to
live with it, but it is an important tool that can be used to compare
antennas, check F/B ratios of beams and other projects. If you have a local
ham who can transmit a steady signal, using the claimed accuracy of the
digital output of 1/10 dB, or even 1/2 dB, you can make meaningful pattern
studies of beams. If you have a SteppIR antenna, you can use that to tweak
the settings or to explore the forward gain vs. F/B issue that all of us
have thought about at one time or another.
Ron Castro
Chief Technical Officer
Results Radio, LLC
----- Original Message -----
From: "Bob Henderson" <bob@5b4agn.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Thursday, September 14, 2006 6:12 AM
Subject: Re: [TenTec] Orion2 Problem with indication of the analog meter
Bill
I'm not sure this explanation holds water.
The 8 bit D to A will reduce that 1/10th dB resolution from the precision
arithmetic to 114/256 dB or just better than 1/2 dB. Unless the S-meter
movement is really bad, there's something else at work here.
73
Bob, 5B4AGN
**********************************************
At times my S-meter doesn't seem very accurate, why is that?
Precision arithmetic is used to calculate the S-meter measurements
and the (digital) output is extremely
accurate. The digital S-meter readings can be read over the serial
port using the ?S command. The
s-meter numeric precision is roughly 1/10 of a dB.
The analog meter is the analog representation of the digital S-meter
result. The meter accuracy is affected
by two things. First, the meter is electromechanical and subject to
manufacturing and environmental
variations. Second, the DSP/Logic board drives the meter through an
8-bit Digital-To-Analog converter
which limits the meter to 256 steps.
***************************************************
The PWR control seems to be fairly accurate
except at the lowest settings. The minimum power I
can set on my Orion is about 4 Watts at a setting of 1.
73, Bill W4ZV
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