[TenTec] O2 output level with PSK aux

wa3fiy at radioadv.com wa3fiy at radioadv.com
Wed Feb 11 15:22:37 EST 2009

A PSK31 signal is a two tone signal.   That likely accounts for what you are 
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.



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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