[R-390] Best approach for SSB mod on R-390A

Les Locklear leslocklear at cableone.net
Sun Jan 3 21:03:10 EST 2010


Actually, the RX-350 sync detector is superior to the RX-340. Having had both side by side for a couple of months, I sold the RX-340. The 350 has good audio, better sync, better noise reduction, better notch filter. Too bad they decided not to keep selling them. The R8B sounded more mellow, but I prefer the 350 1 hz readout and the remote keypad tuning knob set-up.

Most people that own or owned the RX-350 don't understand the filter scheme or how to properly implement the synchronous detector.

It also sounds better than my NRD-545 and the dsp noise reduction is waaaaay better than the 545 which is not very good in that regard.

YMMV

Les Locklear
Hammarlund HQ-180A
Hammarlund SP-600 Re-Engineered by John R. Leary
JRC NRD-545
Ten Tec RX-350
  ----- Original Message ----- 
  From: Cecil Acuff 
  To: r-390 at mailman.qth.net ; 2002tii 
  Sent: Sunday, January 03, 2010 7:45 PM
  Subject: Re: [R-390] Best approach for SSB mod on R-390A


  I think Ten-Tec uses a DSP implementation in the RX-340 and 350.

  Les can report on both as he has owned each and still has one.  Last I heard 
  it was good but still not up to the Drake R8B level..unless I 
  misunderstood...which happens more frequently these days.

  Cecil
  ----- Original Message ----- 
  From: "2002tii" <bmw2002tii at nerdshack.com>
  To: <r-390 at mailman.qth.net>
  Sent: Sunday, January 03, 2010 7:11 PM
  Subject: Re: [R-390] Best approach for SSB mod on R-390A


  > Andy wrote (regarding synchronous detection):
  >
  >>(2) The classy way to do it is put a computer and DSP in the loop where 
  >>the
  >>oscillator is tuned with a D/A converter from the computer. The computer 
  >>and
  >>DSP do digital spectral analysis and look at the signals all around, then
  >>decide what number (frequency) to stuff into the D/A, and consequently 
  >>what
  >>the oscillator frequency should be. This can be made arbitrarily smart,
  >>although more often than not it is still pretty dumb. On some of the $$$
  >>receivers, this "digital detector" is pretty good, like the high-end R&S
  >>offerings these days. Not for the casual listener, of course. If you have
  >>enough DSP horsepower, you do it all digitally with no hardware PLL at 
  >>all.
  >>Being a DSP-head, this is my preferred implementation, but it takes a lot 
  >>of
  >>careful DSP programming to make it work well.
  >
  > It's an intriguing notion, and I'd love to see a good DSP
  > implementation.  I have no doubt that Andy knows lots more about DSP
  > than I do.  Even with substantial DSP horsepower, I've never gotten
  > decent results trying to implement synchronous detection in DSP, nor
  > have I seen a decent commercial DSP implementation (though I have not
  > seen an R&S DSP receiver).
  >
  > Best regards,
  >
  > Don
  >
  >
  >
  >
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