[RTTY] DXP38 vs MMTTY tuning faceoff

[Doug Faunt N6TQS +1-510-655-8604]

I think we've discussed this before.  The DXP38 tuning indicator
sucks.  I use a HAL RTTY=1 with mine, which works much better,although
I find the cross display an affectation.

73, doug

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   Date: Mon, 24 Sep 2001 22:13:34 -0500

   If you're interested, please take a look at
   http://www.qsl.net/wa9als/dxp38.gif

   This is print from a RTTY signal on 20M awhile ago. It sounded fairly weak;
   Although I didn't get a look at the S-meter, it doesn't look that weak on
   the MMTTY display.  The window on the left is MMTTY in default profile, and
   the one on the right is from the DXP38.

   They aren't getting the EXACT same audio, because I didn't parallel it.
   Rather the soundcard is getting it from the ACC connector on the rig (fixed
   level), and the DXP is getting audio from the speaker out jack of the rig
   (sensitive to AF gain control).

   Anyway, what I find interesting and confusing are the TUNING indicators.
   The DXP was set to delta-f mode and tuned to center.  As I recall, each LED
   segment is equal to 50 Hz, so a properly tuned signal in the delta-f display
   should be within 50 Hz.  However, look at the MMTTY display (AFC OFF).  It
   obviously doesn't agree that the signal is properly tuned.  I guess the
   off-peaks amount in the MMTTY display might only represent about 50 Hz, so
   maybe they agree better than I first thought.  I didn't get a chance to tune
   to the MMTTY display and see if the DXP was still centered before they
   signed.  (It's sure difficult to play with this stuff when noone's on the
   air!  HI)

   Even less than perfectly tuned, the print in the MMTTY window was sure
   superior.

   I don't consider this a fair face-off of the demodulators, but I'd like any
   comments on the tuning displays.

   Thanks!  73 - John


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