[Elecraft] RE: PSK31 Power Level

[David Wilburn]

It has been a while since I did PSK, but I believe the driving factors 
for his statement has to do with duty cycle and output power.  Since PSK 
  is at a higher duty cycle (the PA is effectively transmitting more 
power over a longer time) that they suggest you reduce the power to 
reduce the effect on the PA's and associated circuitry.

As an example, all the lasers that are carrying the bits and packets on 
the optical backbone to the Internet, all use "Manchester coding". 
Where a 1 or 0 is represented by either a square wave shifting high, or 
shifting low.  Instead of just a high or low.  That way the transmitter 
is at low power for half of every cycle.  There by reducing the duty 
cycle, and the demand on the system by half.

David Wilburn
dave.wilburn at verizon.net
K4DGW
K2 #5982


Parker Buckley wrote:
> Don,
> 
>  
> 
> It's that "idle tone" that I question.  If I push the Tune button (Digipan)
> I get a single tone.  If I push the T/R button, I get a dual warbling tone
> which gives about half the reading on the wattmeter (probably something like
> an average of the two warbling tones and some off period between them).  So
> you're saying to bring up the single tone to only five watts?   That puts
> the warbling tone down to the 2-3 watt level.  I guess the peaks are
> probably hitting the five watt level, but the meter can't keep up.
> 
>  
> 
> Thanks,
> Parker
> 
>  
> 
>   _____  
> 
> From: Don Wilhelm [mailto:w3fpr at earthlink.net] 
> Sent: Sunday, February 25, 2007 6:23 PM
> To: Parker Buckley; W3FPR - Don Wilhelm; Elecraft at mailman.qth.net
> Subject: RE: PSK31 Power Level
> 
>  
> 
> Parker,
> 
>  
> 
> The best for running PSK31 is to set the power knob to 10 watts or above.
> 
> Then adjust the level from your computer soundcard so your power meter goes
> up to 5 watts with the idle tone.  There should be no ALC bars showing.
> 
>  
> 
> Also, be certain that you have the compression set to 1:1.  If you are using
> the RTTY mode, there is a separate SSBCr setting in the menu, and that is
> independent of whatever compression level you may be using for SSB.  If you
> are using the RTTY filters, remember that there is yet another set of 4
> filters that need to be properly set up for width (use the OP1 filter for
> FL1 - that is important), and set the remaining filters whereever you would
> like in terms of width and filter center.  Use Spectrogram and it is easy.
> 
>  
> 
> If you want to increase the gain for the KDSP2 again for whatever reason,
> you may have to add a divider at the two inputs of the Fixed Audio board -
> something like 2.2k in series and then 2.2k to ground should give you good
> results.
> 
>  
> 
> 73,
> 
> Don W3FPR
> 
> -----Original Message-----
> 
> Elecrafters,
> 
>  
> 
> Don has been coaching me off-list through installation of one of his fixed
> audio output kits, which I've had around here for many months, un-built.
> All went well, except the audio through my computer was distorted.  I
> eventually tracked it down to the K2 DSP gains being set too high.  I was
> getting away with that in the basic K2, but the fixed audio unit doesn't
> like being pushed that hard.  I've now carefully reset the DSP gains to get
> the same audio level with DSP and with DSP bypassed.  Everything is working
> great.  I'm now reminded of a nagging question since the last time I strayed
> from CW to PSK 31.  I've read numerous places about setting the power level
> (mine is a QRP K2) to five watts for continuous use like PSK.  Does that
> mean five watts for single tone like CW, or five watts average as the two
> tones warble back and forth?  I'm using a WM-2 wattmeter in the output.
> Running about 10 watts single tone, I get about five watts warbling and a
> single ALC bar flickering.  Is this okay, or should I back it down to five
> watts single tone?  I thought this question might be of interest to a wider
> audience.
> 
> Parker
> 
> WD8JOL  K2 #2636
> 
>  
> 
> ...back to work tomorrow, and peace for Don.
> 
> _______________________________________________
> Elecraft mailing list
> Post to: Elecraft at mailman.qth.net
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft    
> 
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>