With the PSK31 signal in IDLE, it is a two-tone which has a peak to average
power ratio of 2:1.
So, your output will show 10 watts in idle - when not sending any
characters from the keyboard - while the peak power will be the 20 watts
maximum that the rig is capable of putting out while meeting specs on
distortion, etc. I do not know why your Argo only indicates 10 watts output
in TUNE, unless you are saying TUNE when the program is actually in IDLE
mode.
It is like sideband, in that if 20 watts is the peak power limit, the duty
cycle of speech - combined with the time lag in meters, etc. - is such
that you may indicate only 3 - 5 watts output while talking. The two-tone
signal has the convenient math property of that 2:1 ratio so that we know
exactly what the meters will read when that is the signal form and *there
is no distortion*.
If you have a good peak-reading wattmeter, set up the rig to output a 20
watt PEP signal with the PSK31 IDLE signal. Now, switch from PEP to Average
Power and you should see the meter reading drop to 10 watts. IF it does
not, either you have distorted the waveform - usually by overdriving some
stage and flat-topping or clipping the waveform - or your wattmeter is not
properly displaying the difference between PEP and average power.
YOu may well find that you need to reduce the PEP output of the Argo to
around 10 watts under IDLE conditions in order to obtain low 3rd-order
distortion products. I run my Icom 756 PRO at no more than 40 watts PEP
maximum on PSK31. Above that, the IMD increases too much. Usually output is
actually only 30 watts PEP or 15 watts average on IDLE. Get better than -35
dB IMD readings that way.
73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489 Icom IC-765 #2349 Icom IC-756 PRO #2121
Mark Erbaugh wrote:
>
> What experience have folks had with the Argo on PSK31? I've made a couple of
> contacts, so I know that it's working.
>
> I used the same interface that I use for PSK31 with my Pegasus (the Argo V
> has the same connector). My interface includes pots to adjust the Tx level,
> so it wasn't a problem to compensate for the mic level input to the Pegasus
> and line level into the Argo.
>
> Adjusting power was tricky, or maybe I don't understand it. With the Argo
> power set at max, I put my PSK31 software (Digipan) in TUNE mode and
> adjusted the audio level until the ALC light was out but just on the verge
> of coming on. I assume that this is the max level before the signal would
> start to be distorted from ALC action. The max power (according to the
> Argo's meter) was only around 10 watts. Shouldn't it be 20 watts, which is
> what I get key down CW?
>
> Then if I back off the Argo power, the ALC light starts to come on and I
> have to back off the audio level. It looks like there's really no reason to
> use the power setting, just leave it at max and adjust the audio level to
> get the desired power. Would this work?
>
> 73,
> Mark
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