Stereo-RTTY: Is It Possible? (What can We Do with it?)

Since January, I have been learning the In's / Out's of a newly acquired Yaesu FT-2000 Transceiver.  Like its predecessor (the FT-1000mp) it effectively utilizes in-band dual-RX, making possible an operating technique known SO2-V: Single-OP 2-VFO's.  When running Cw or Ssb, I can either operate SO2-V (with RX-A audio to the Left-Ear and RX-B audio to the Right-Ear) or, I can run
things using the Stereo-Cw/Ssb method(s) I have written so much about.

With both the FT-1000mp and the FT-2000, SO2-V is largely a no-Brainer, regardless of the mode; even mixed-mode (Cw / Ssb for example); I can run a frequency with one VFO while S&P'ing
with the other.  The array of external audio & DSP filters enhance these methods considerably.

However when it comes to actually decoding RTTY, by default, external audio filters are of no
use as RTTY decoders (like the RigExpert Plus unit I use) take their audio input BEFORE the
audio is sent to the audio output jacks on these radios.  In preparation for Part II of this Blog
series on Stereo-RTTY, I will find a way to intercept the RX-audio line for the RigExpert decoder. 
By redirecting this line to an RCA plug/jack arrangement the external filter array can be "inserted"
into this audio line, enabling peaking/notching the audio-data stream to make it more QRM/QRN
free and therefore the data becomes more easily decoded.

Using the Stereo-Cw method, with the filters properly adjusted, multiple calling stations seem to appear (spatially) at different "locations" in the listening experience.  While I can use the clarifier (CLAR) knob to position a signal at an audio frequency that one of the PEAK filters can peak into "better" readability, usually it isn't necessary, in order for my brain to "decode" a given Cw station.

With RTTY it is a different situation altogether; in order to achieve proper/accurate decoding, the station must be tuned-in more-or-less precisely on the correct frequency for the individual tones
to be properly decoded.  It is for this reason that Stereo-RTTY has different operating objectives.

Because the essential benefit of the "Stereo" concept is to have calling stations arranged "around" the operating position in a more-or-less 180-degree azimuth arc, I have questioned the value of stereo audio in a RTTY contest.  As it turns out, Stereo-RTTY is most useful when calling stations are off frequency.  When you think about it, if several stations are calling on EXACTLY the correct frequency (as they should be), they will jumble over each other, making proper decoding tricky at best.

With Stereo-RTTY, the idea is to adjust the Peak Frequency of the external filters (which for WQ6X
is a pair of Autek QF-1A's) such that the signal "appears directly in front" of the operator.  Off-frequency calling stations will appear "to the left" and "to the right".  We of course use the (CLAR) control for tuning-in the station until property RTTY-decoding is achieved.  With Stereo-RTTY, the listening "position" of that station should shift more-or-less towards the center of the listening experience.  The individual RTTY tones should "appear" more-or-less on either side of the center listening experience.

Because all this is being accomplished using the PEAK function of the external filters, theoretically the signal/noise ratio should improve, enhancing the decoder software's ability to interpret relatively weak signals.  Prior to inserting the QF-1A's into the RTTY audio line, the improved listening-aesthetic was discovered which led to the question of whether or not [so-called] Stereo-RTTY
could actually improve operating efficiency.

I invite you to use a pair of (ideally identical) audio filters to hear what Stereo-RTTY actually sounds like; if you like it, then insert those filters into the decode-audio line and take your RTTY operations
to the next level, in the same way we did with Stereo-CW.

[CLICK HERE] to read Part 2.