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[TenTec] RX-340 and Noise Reduction

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Subject: [TenTec] RX-340 and Noise Reduction
From: aa5f@hiwaay.net (Jim)
Date: Mon, 11 Feb 2002 21:34:19 -0600

I have compared the Timewave 59+ and the JPS NIR 12 with TT's inboard
Omni VI+ DSP. (As far as I could tell, the difference between the 59+
and the 599zx are the controls.) 

On CW, the Omni VI+'s seemed to do a better job of increasing the volume
of the desired signal than did the 59+. The 59+ does a creditable job of
lowering background noise without increasing the desired signal. So if I
turn on the 59+ and increase the volume, the units are comparable. I see
no reason to use the 59+ with the Omni VI+. (I use it with my Corsair

On SSB, the NIR 12 does a better job of reducing noise than either the
TT or the Timewave. But it introduces a time delay that makes sending CW
difficult. So I use it with my Omni VI+ on SSB only.

Neither unit is very expensive now, especially in comparison to what you
have already invested. It would be worth a try. Please keep us posted.

                        Jim  N4AL

Jim Reid wrote:
> Hi all,
> Have had the 340/Pegasus set up for about a month now.
> Biggest "con":   no DSP noise reduction option!!
> The Omni VI+ has a beautiful NR function,  particularly
> for CW,  but nothing on the 340.  Where I live,  there is
> essentially no "man made"  RF noise to worry about,  but
> we are also a loooong way from any DX (Hawaii is the most
> isolated QTH on the planet,  nothing closer than a few
> thousand miles).  So,  DX is often weak,  lots of F layer
> hops to get here,  but bounces off the ocean help,  hi.
> Anyway,  I wish for my Omni NR button back!  Now,  would
> a Timewave 599zx substitute??  The 340 AGC, is wide open
> on a dead band,  and the audio noise output is very high.
> Connecting to the dummy load,  still a lot of noise out.
> The 340 meter reads at the noise floor,  - 135 dBm or so,
> but the IF and audio gain bring it up loud.
> The Timewave specs specify the DSP noise reduction is
> about 20 dB.  If I turn down the "RF" gain of the 340 20 dB,
> I don't see a really noticeable noise reduction,  but this might
> not be the same thing.  Don't know what the NR reduction
> in the Omni VI+ using their algorithm might be;  ARRL did
> not test it in the 1997 review,  nor is their any info in their
> "expanded" test report about the DSP NR in the Omni.
> So,  is it a good idea to buy a Timewave to mate to the
> RX-340?
> 73,  Jim  KH7M
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