Having operated PSK-31 with the Omni VI Plus for quite some time, I fed the
audio into the rear panel connector direct from the sound card output. I
used a L pad consisting of a 10K series resistor with the audio line and a
1K to ground at the audio input to the radio. These resistors were 1/8 w
and mounted inside the RCA connector shell. I would set the power output
in the TUNE mode for max or about 100 watts. Then with the MIC gain at
about the same position I used for the mike for SSB, I would adjust the
output of the sound card to produce about 35 watts with the PSK tones. I
always would receive -25 to -30 dB IMD values from the receiving station
while at idle or no data being sent. In all cased, do not have the Speech
Processor engaged and you should not see any ALC LED action with data. Do
not change the power setting on the radio. It should always be at MAX
setting. Instead, change the audio from the computer to the radio to get
the desired power output.
As to heat, a fan on the heat sink is always a good idea, more to prevent
the inside of the radio from heating and causing some frequency drift of the
BFO oscillators. One of the 2" to 3" computer processor fans that operated
from the 13.8 volt supply and supported by some plastic screw anchors {the
kind used in drywall} and shoved in the fins of the heat sink worked well.
I used a #6 screw through the mounting holes of the fan and into the
anchors. Made for a quiet, no holes installation. Make sure the fan
directs the airflow into the heat sink. If the fan runs too fast and makes
too much noise, simply insert 2 or 3 silicon diodes in series with the
power to the fan. This drops the voltage about 1.5 to 2.2 volts depending
on the number of diodes in series. Just make sure that you don't drop the
voltage too much or the fan may fail to start.
73
Bob, K4TAX
----- Original Message -----
From: "Paul" <designer@quickdata.com>
To: <tentec@contesting.com>
Sent: Tuesday, January 13, 2009 10:27 PM
Subject: Re: [TenTec] Omni VI Opt 3 PSK 31 Operation
> The trend used to be, run at low power and turn up the mic gain (with
> the two tone TUNE signal) until the ALC light flickers, then back it
> off a hair. But current trend posts in digital news groups seem to
> say run the rig wide open but using the mic gain and a two tone PSK
> "tune" output, adjust so you are only putting out the 15 - 25 watts
> (whatever the duty cycle will allow, not over 40 W or so). Something
> about improved linearity.
>
> I used the ALC method on my Argo V and ran about 15 Watts and the ALC
> flicter method. Always got good reports and could easily get into
> South America from Central Oregon. And getting anywhere from Central
> Oregon is an accomplishment. You do NOT need high power on PSK and in
> fact it will only be bad for your signal and bad for your rig. PSK
> is one place where the "playing field" is still pretty even.
>
> 73,
> Paul
> _______________________________________________
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> TenTec@contesting.com
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>
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