I observed the same things in my O2 regarding the power output readings.
While the meter only seems to be accurate at the 100 Watt level, the power
setting control is amazingly accurate. Using both a Bird 43 and a Telepost
LP-100 the settings agree with the true output power within 2% to 5% from
about 20 Watts to 100 Watts CW out.
Ron N6IE
www.N6IE.com
----- Original Message -----
From: "Merle Bone" <merlebone@charter.net>
To: <tentec@contesting.com>
Sent: Wednesday, February 11, 2009 9:49 AM
Subject: Re: [TenTec] O2 output level with PSK aux
>I think it is very hard to know what the "power readings" of the Orion
>meter
> really mean. Actually, most,
> if not all, of the Orion meter readings are "relative." The power meter
> description says"
> ----------------------------------------------------------------------------------------------------------------------------------
> ANALOG METER
> In transmit, the meter shows approximate output power (+/- 5%). The power
> meter is
> a sampling-type meter and will stay more or less constant when sampling
> power output,
> particularly when the transceiver is used in CW mode."
> ----------------------------------------------------------------------------------------------------------------------------------
> I take from this description that the meter is "some form" of average
> reading meter. All Orion/Orion II
> meter readings are really from "calculated" numbers from the DSP and then,
> through a Digital to Analog
> converter, drive the analog meter. "Average" meter readings are always a
> function of the "averaging time constants"
> in the meter and the "time varying levels" of the waveform being measured.
> These are almost never the same
> and, unless you are using a "very high sampling rate meter" - like the
> LP-100- that then does the math to
> compute an average, the readings are - at best - relative and approximate.
>
> I never use the Orion meter to give me power readings, except on CW,
> because
> I have never figured out what
> they really meant. I think on "time varying signals," you are better off
> to
> use an external "peak reading meter"
> to set the Orion peak power and then accept the average power that results
> from the time varying input signal.
> If there is concern for "intermodulation distortion," then you can reduce
> the peak Orion RF power to a level where
> you believe the Orion will be "most linear," - maybe down 3dB to 6dB below
> the Orion's rated RF power output.
> Of course, this doesn't ensure a clean output signal. You can reduce the
> Orion RF peak power output and still have
> an audio overdrive situation - creating signal distortion in the audio
> before it gets to the RF drive of the Orion.
> In the case of signals that are very sensitive to distortion, such as
> PSK31,
> an external monitor - such as the
> "PSK31 Meter" display monitor may be more useful then power meters to
> assure
> a good output signal. If you
> have a time varying signal like voice, then you can use the Orion
> compression, with a high sampling rate, - which
> is some of the best I have ever seen for voice (See
> http://lists.contesting.com/archives//html/TenTec/2009-02/msg00075.html )
> - to increase the average RF Orion output power. The Orion meter still is
> only giving a "relative" power measurement.
> 73, Merle - W0EWM
>
>
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