[TenTec] O2 output level with PSK aux

Merle Bone merlebone at charter.net
Wed Feb 11 12:49:41 EST 2009

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"
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 

More information about the TenTec mailing list