Q-Filtering for Fun and Profit - Part 3: The Journey Continues

For this WQ6X Contest Blog, I have written over a half-dozen BLOG entries on the various
aspects of audio filtering and how to leverage it for contest activity; in particular running SO2-V. 
Thus far, this particular BLOG series has been written during two separate evolutionary periods
of WQ6X station development @ W7AYT's QTH along with various flavors of remote operation
of STN-1 at NX6T in Fallbrook.  You may remember the first two installments of this Blog Series:

• [x] - Q-Filtering for Fun and Profit (March 2018)
• [x] - Q-Filtering for Fun and Profit - Part 2:
           What I've Learned So Far (August 2018)

Related BLOG entries include:

• [x] - Stereo-CW - it's EASIER than You Think  (March 2018)
• [x] - LEARNING the ART of LEVERAGING DUAL RECEIVE (May 2017)
• [x] - The world of SO2V - some thoughts by a newbie operator (July 2017)
• [x] - The DR. Validates Cascading Filters (March 2018)
• [x] - WQ6X SOUND PROCESSING:
          SOUNDING OFF about SOUND (December 2018)
• [x] - Analog or Digital Audio - Which should we choose? (December 2019)

With all that has been written (above) you might think I have said all there is to say on the subject. 
In fact, re-reading those above BLOG entries got me to thinking about where this combination of analog/digital technology will fit in to the WQ6X operations during 2020 and beyond.

While most of the WQ6X operations are run as a portable setup from W7AYT's QTH in Concord,
test running the various filter combinations actually occurs in Alameda first; then, the best of the
best make their way to the Concord operation. 

Currently under evaluation is [yet] another Autek QF-1A filter - for processing audio to the Left Ear,
in conjunction with an old MFJ-751 (the predecessor to the MFJ-752) for processing audio to the Right Ear.  A 4-position audio switch allows switching laptop internet audio to a pair of cheesy i-Sound speakers, or to a pair of wireless headsets - either directly or through the QF-1A / MFJ-751 filter units.

In December, I brought my old ICOM-7000 radio to join the setup in Concord.  Altho the ICOM
unit can be switched through the external filter setup, thanks to a fully featured DSP filter setup,
the QF-1A filters do not show as dramatic effect as would be experienced otherwise. 

Then again, while the 7000's "mimic" of the 756-PRO III radio's DSP is truly AWEsome, the SHARP Peak filter in the QF-1A can "pull" weak stations out of the audio-mud in a way that no DSP circuit can equal.  It is for this reason I prefer utilizing Analog & Digital processing during intense contest periods; my ears need all the assistance they can get.

In Part-1 of this series I mentioned the classic Heathkit QF-1 Q-Multiplier.  After renaming it the HD-11 with a color scheme to match the Mohawk RX, the unit underwent one more evolution to the GD-125 matching the SB-series of equipment. 

It recently occurred to me that being a 455-kc circuit, it should be possible to run the GD-125 on
the FT-1000mp's Sub-RX, effectively providing a sort-of "Analog-DSP" at the IF-level, something absolutely necessary for improved SO2-V operation.  The test run of this concept will be with the
RC-71A receiver at my Alameda location.  While the RC-71 already has a notch, the GD-125
should nevertheless be able to augment the 455-khz 2nd-IF.

Thanks to the immense computer-controlled technology found in most radios in the last 35 years, I no longer have the technical acumen to effect much in the way of repairs.  When I accidently hooked the ICOM 7000 (fuseless of course) reversed polarity to a marine battery during Field Day, opening the unit it was clear to me that I lacked a steady hand to effect proper soldering on such a miniature circuit board, requiring ICOM service to bring the 7000 back to life.

However, I CAN make dramatic improvements to most ANY radio I come across by way of external audio/Dsp filters.  Being a "knob twiddler" I love being able to make filter adjustments with the hope of bringing about signal readability that might not be possible otherwise.  As I have shared in this BLOG series, some of the best QRM-ridding technology is over 2 generations old, yet it frequently surpasses the computer-based DSP circuitry found in today's transceivers.

I guess what goes around [eventually] comes around.  LooK for a Part-4 in this series reporting on the successful adaptation of 1965 technology (the GD-125) into 1985 technology (the RC-71A) 35 years later in 2020.

Do YOU like to spend time with external audio filters?

If SO, what lessons have YOU learned?