How Stereo-Cw becomes Stereo-Ssb

 

 

 

 

 

 

In the last several years I have been experimenting with the concept known
as "Stereo Cw".  Several Blog entries have been written about this topic,
including:

• [X] - WQ6X Sound Processing: Stereo CW - it's EASIER than You Think
  
• [X] - Some Further Thoughts regarding Stereo Cw
  
• [X] - Leveraging the Art of Dual Receive - Another Look (with additional Blog links)
  

Instead of building the circuit from the original article, the fixed-filter circuits have been
replaced with a pair of classic Autek QF-1A analog filters purchased at approximately $35/ea. 
The QF-1A approach allows for a continuously variable stereo shift effect.

 

 

 

 

 

 

 

 

 

After all these years, I'm still amazed by signals shifting from one ear to the other as a given signal
is tuned through.  Listening to the Russian military beacons on ~7.039, it is possible to hear the
3 beacons at "different locations" in the listening experience.

During a recent ARRL Dx Ssb contest, it occurred to me that a similar effect can be created for single sideband.  This was demonstrated from my Alameda remote operation QTH, which also sports a pair of QF-1A filters.  (As you might have guessed, I have high regard for these classic Autek filters.)

With the filter pair properly adjusted, a properly tuned-in signal appears in the "center" of the listening experience.  On LSB, signals slightly higher in frequency (low-pitched) appear on the left-side of the listening experience while stations slightly lower in frequency (higher in pitch) appear on the right-side.  The reverse is also true for USB; stations higher in frequency (lower in pitch) appear on the
left-side, while stations lower in frequency (higher in pitch) appear on the right-side.

Some operators have difficulty tuning in Ssb signals.  With the audio filters properly balanced,
it becomes easier - just tune the station until the voice sounds natural and appears in the "center"
of the listening experience.

During the ARRL Ssb Dx contest, Asian stations were notoriously off frequency.  Using the R-I-T control allowed me to tune those off frequency stations into the center of my listening experience allowing proper copy of their exchange.  Clearing the R-I-T quickly sets the receiver back to its
REAL center-point.

While I love the DSP circuits of today's radios, there is NO DSP that actually allows for stereo
audio filtering as described above.  Luckily, external filters are relatively inexpensive.  Currently
at the Concord location two different sets of filters are used: the MFJ-752 Signal Enhancer II and the Autek QF-1A.  The MFJ-784 and the JPS NIR-12 DSP units (also in the above picture) can probably also provide a stereo effect, altho because their major focus is Noise Reduction and Notch Filtering, adjusting for stereo is NoT so intuitive.

Stereo audio (whether for Cw or Ssb) provides another level of excitement to amateur radio operations; not JUST for radiosport contesting, but for simple ragchewing and shortwave listening.

Have YOU tried Stereo Audio yet? 

It's EASIER than you think.