Re: [amsat-bb] DSP Noise Reduction on Receive

["Rick Fletcher" <rfletcher@xxxxxxxxxxxxxx>]

I have both the ClearSpeech Base and the Timewave DSP-599zx.  Both do a
better job pulling SSB signals out of the noise than does the DSP built into
my Kenwood TS-2000X.  On voice, I'd give the edge to the ClearSpeech but for
data, including AO-40 telemetry, the winner hands-down is the DSP-599zx
(successful decoding of data signals after ClearSpeech processing is very
hit-n-miss whereas the DSP-599zx made it possible to copy AO-40 telemetry
when noise had otherwise made doing so impossible).  Auto-notching of
heterodynes is another plus for the DSP-599zx.

73,

Rick
KG6IAL

----- Original Message -----
From: "Jon Ogden" <na9d-2@speakeasy.net>
To: <amsat-bb@AMSAT.Org>
Sent: Sunday, February 09, 2003 3:11 PM
Subject: [amsat-bb] DSP Noise Reduction on Receive


> Hi gang,
>
> I decided to try an experiment this afternoon and see how well my Timewave
> DSP-599zx works for improving the audio SNR on AO-40 signals.  Here's what
I
> found out:
>
> For the beacon, the Timewave is not very useful.  It appears that the
> Timewave filter response has a suck-out right around 1000 Hz.  I'm not
sure
> why, but no matter how you tweak either the High Pass or Low Pass
> adjustments, it doesn't take that out.  From what I can tell, it looks
like
> that part of the audio spectrum is needed to properly decode the beacon.
>
> On voice Qs, the DSP works great.  The random noise reducer made the
> difference between being able to hear people and not.  The squint during
the
> 4 or 5 Qs I had was about 25 degrees.  If I took the random noise reducer
> off, I would be able to tell there was someone talking to me, but it would
> be pretty much unintelligible.  Even if I could copy the signal, adding
the
> NR would help tremendously in listening comfort.
>
> While I have an FT-847, I am not using it in receive (using an FT-817
> instead for RX) so I cannot really compare the two DSPs.  Although I
believe
> the Timewave is far superior.
>
> I have ordered a ClearSpeech II base unit.  Hopefully it will be in this
> week.  I plan on adding that in the audio chain and I will report on how
it
> helps too.  From what I remember from playing with it at Dayton last year,
> it blows the Timewave's random noise reducer out of the water.
>
> So for those of you who have external DSPs, try them out and see how much
of
> an improvement you get in received audio.
>
> 73,
>
> Jon
> NA9D
>
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
>
> Citizen of the People's Democratic Republik of Illinois
>
> Life Member: ARRL, NRA
> Member:  AMSAT, DXCC
>
> http://www.qsl.net/na9d   <- Updated on 1/22/03!!!
>
> "A life lived in fear is a life half lived."
>
>
> ----
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