[hpsdr] Pennywhistle bias setting

[David McQuate]

Filtering can attenuate harmonics, but cannot suppress the results of 
intermodulation distortion produced by the amplifier.  Both KISS Konsole 
and PowerSDR can produce a two-tone test signal.  The bias can be 
adjusted by observing the amplifier output on a spectrum analyzer for 
minimum IMD.  KISS Konsole can run in full duplex mode so that it can 
simultaneously transmit and receive, allowing IMD adjustment with no 
additional test equipment.   (Be sure to use plenty of attenuation 
between Pennywhistle output and Mercury input!)
73,
Dave
wa8ywq

Gerald J. Herman wrote:
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> Finished Pennywhistle assembly and going through Adjustments. The 
> quiescent current is to be set at 450 mA per transistor which seems 
> rather high to me. This amounts to approximately 12 watts of power in 
> the quiescent state. I suspect the effect of lower currents and their 
> effects on harmonics was investigated by someone who has the 
> appropriate equipment. Since filtering is required after the amplifier 
> anyway to make it legal, would it be possible to run lower currents 
> and reduce the quiescent heating and power draw, and still be legal?
>  
> Wonderful kit and a joy to assemble. Thanks to everyone involved.
>  
> 73,
>  
> Gerry
> KR8W
>  
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