[TenTec] O2 output level with PSK aux
wa3fiy at radioadv.com
wa3fiy at radioadv.com
Wed Feb 11 16:04:53 EST 2009
Good point about the PSK idle. I knew that and failed to mention it. When in PSK
idle, it is indeed a two tone signal and shows about 50% of PEP on many power
meters. When sending data, I'm not sure how to describe the signal but it does show
a little more than 50% of PEP on many meters.
I do not set the Orion (or other Ten Tec rigs) for 100 watts output for two reasons.
First, by setting the power to 50 watts or less, I automatically limit the maximum
power I can put on the band. Actually, I usually set it to 30 or 40 watts. Otherwise,
with no power limiting, power output can drift upwards as you operate and as the
various circuit components warm up, and next thing you know, you are an alligator on
Secondly, I find almost no IMD penalty in allowing a small amount of ALC action.
Maybe 1 or 2 db. I did extensive testing a number of years ago with my Pegasus
and posted the results here. They are in the archives somewhere. :-) I recently did
a presentation at our local radio club meeting and we saw IMD readings in the low to
mid 30's with a fair amount of ALC action, still using the Pegasus. Furthermore, I
have tested the Orion and it performs equally well in this regard.
So, I guess it's a matter of personal preference with regard to using the ALC on late
model Ten Tec radios. I have no knowledge of the performance of other radios
though. They may or may not be more sensitive to ALC action in regards to IMD
On 11 Feb 2009 at 14:45, Bob McGraw - K4TAX wrote:
> I agree with all, except.......... set the Orion power output for 100 watts
> in the CW mode and then adjust the audio from the computer or interface or
> Line Gain to produce an output of 45 to 50 watts max during data
> transmission. Remember, when using the PWR control this is basically setting
> the ALC level threshold.
> Yes the Orion meter and the Omni VII meter will show darn near correct PEP
> values with a PSK signal while external mechanical meters will likely show
> average values or something less than depending on mechanical ballistics,
> rectifier/detector characteristics and the weighting network. I've found
> that the internal power indication is usually a bit lower than the actual
> output. I attribute this to the scan rate of the processor looking at the
> power circuit. At the same time an external meter like the Bird 43P looks
> at the power 100% of the time.
> Also the PSK signal idle will show a lower average level than when sending
> data although the PEP values are the same. I think most reports on PSK are
> average power values. And yes if the IMD level is not running in the 30's
> with the Orion, Jupiter and Omni VII then all is not well with your
> transmission. Just ask the receiving station to give you and IM report.
> Send about 10 sec of idle and see what the number are. Data values will be
> in the 20's.
> Bob, K4TAX
> ----- Original Message -----
> From: <wa3fiy at radioadv.com>
> To: <jmiller1706 at cfl.rr.com>; "Discussion of Ten-Tec Equipment"
> <tentec at contesting.com>
> Sent: Wednesday, February 11, 2009 2:22 PM
> Subject: Re: [TenTec] O2 output level with PSK aux
> >A PSK31 signal is a two tone signal. That likely accounts for what you
> > seeing on the 'scope. That also accounts for the lower average power
> > output reading compared to a CW output. Somebody check my theory but I
> > think a two tone signal of two equal amplitude tones having the same PEP
> > as a continuous carrier will have an average power of 1/2 the continuous
> > carrier. Anyway any radio that is transmitting a PSK31 signal and is
> > showing more that about 50% of the continuous carrier is non linear and
> > should not be used or better, readjusted to operate in the linear range.
> > On
> > my Orion here (and several other rigs as well) I set the O for 50 watts on
> > CW with the PWR control. The Power output meter shows about 52 watts.
> > Makes sense. My external power meter agrees. When I run a PSK31
> > signal JUST barely lighting the ALC led, I still show 52 watts on the O
> > power
> > meter and about 25 watts on the external power meter. That too makes
> > sense if indeed the PSK two tone signal average is 50% of PEP. My SB-
> > 610 scope confirms that the CW PEP power and the PSK PEP power are
> > identical. This tells me that the O power meter displays PEP output and
> > agrees very well with the setting of the PWR control.
> > I have often wondered about PSK31 power reports. When an operator
> > says he is running 30 watts what is he talking about? 30 watts average
> > or
> > 30 watts PEP? 2:1 difference. Not that it makes much difference. Just
> > curious. I always report PEP which I can read directly off the O power
> > meter or the PWR control as long as I am tickling the ALC. Finally, it is
> > OK
> > to get a small alc indication on several Ten TEC's I've tested. On both
> > my
> > Pegasus and Orion, I consistently see IMD levels in the low 30's which is
> > pretty good signal.
> > 73,
> > -Lee-
> > On 11 Feb 2009 at 15:49, jmiller1706 at cfl.rr.com wrote:
> >> Thanks to all for the suggestions. On RTTY AFSK (basically a constant
> >> carrier)I do get about 80-90 watts out on second measurement, with
> >> Navigator set to max outputs. The Navigator still seems to be a bit
> >> light on drive for an Orion however. Now, looking at PSK on a scope, I
> >> see that it is not exactly constant amplitude when idling, as I had
> >> assumed erroneously previously - seems to have a slow sine modulation
> >> envelope on it. I assume that's normal (?). This could account for the
> >> lower average power reading on the wattmeter in that mode. When I set
> >> the wattmeter to peak/hold, it shows close to 90 watts (by capturing the
> >> peak). Of course that's too much, but I think that explains some of the
> >> discrepancies.
> >> N4BE
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