[Elecraft] Headphone Output - SSB Mode - Single Tone

[Joe Subich, W4TV]

Jack, 

> The short story is 2nd harmonic is at least 80 dB down and the 
> 3rd harmonic is 76 dB down. Fourth and fifth harmonics are in 
> the noise and not visible. An artifact at 3.9 KHz is also visible, 
> although quite far down compared with the desired signal.

That is remarkably close to what I measured with my K3 in CW with 
a Heil Proset as the load.  I posted those results on Thursday.  
I've run them again in USB with a 500 Hz reference tone. 

DSP is set to 2800, center frequency is 1500 Hz (default).  Signal 
source is an XG-2 (50 uV/-73 dBm) and ACG is Slow.  

 200 Ohm (Heil Proset) headset 

   500 Hz     ---------------- Harmonic -------------------
 Reference    2nd   3rd   4th   5th   6th   7th   8th   9th 
 ============================================================
  +4 dB       -64   -45   -79   -47   -81   -49   -78   -51
  +3 dB       -66   -78    nf   -83    nf   -92   -98   -93
   0 dB       -68   -79    nf   -82    nf   -89   -95   -93
 -10 dB       -76   -75   -80   -82   -84    nf   -86    nf
 -20 dB       -72    nf   -73    nf   -75    nf   -76    nf  
 -30 dB       -64    nf   -62    nf   -65    nf   -66    nf  
 
0 dB is .7 V RMS (1V Peak) measured for the reference tone 
across the headphone element - total audio level will be 
somewhat higher with distortion/noise.  "nf" indicates the 
harmonic product not measurable (in the noise floor). 

Note: at +4 dB, the audio amplifier is in clipping and there 
are additional IMD products approximately +/- 200 Hz from the 
reference and each of the odd harmonics. 

73, 

   ... Joe, W4TV 
  





> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jack Smith
> Sent: Saturday, September 06, 2008 2:14 PM
> To: Paul Fletcher
> Cc: elecraft at mailman.qth.net
> Subject: [Elecraft] Headphone Output - SSB Mode - Single Tone
> 
> 
> At the request of Paul, M1PAF, I've measured the harmonic distortion 
> seen at the headphone output in a K3 operating with with 2.7 KHz 
> bandwidth USB mode with a single tone at 500 Hz offset. This 
> allows up 
> to the fifth harmonic to be within the DSP passband.
> 
> The details are at 
> http://www.cliftonlaboratories.com/elecraft_k3_receive_audio.htm.
> 
> Audio level is set for a comfortable listening level with a Heil 
> Pro Set, corresponding to about 30 mV RMS.
> 
> The short story is 2nd harmonic is at least 80 dB down and the 3rd 
> harmonic is 76 dB down. Fourth and fifth harmonics are in the 
> noise and not visible. An artifact at 3.9 KHz is also visible, 
> although quite far down compared with the desired signal.
> 
> Jack K8ZOA
> www.cliftonlaboratories.com
> 
> 
> 
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