George,
Yes, the DSP dynamic range of the RX340 is 40 DB. The listing
I saw recently on this reflector for a lot of different radios, indictated
that the PRO had a close in dynamic rane of 60 DB. The rx340
DSP processor is 16 bit processor. Each bit is worth 3 db, not
6 db. So that would yield 3*24 or 72 db for the PRO and 3*16
or 48 DB for the rx340. Both are a little less for other reasons.
The rx340's main strength comes from the outstanding AGC
circuit ahead of the DSP chip. It's amazing, but I really think
most of our s meters are miscalibrated and the strongest signals
tend to be more like s9+20 and not s9+40 as our meters tend
to read. Anyway, I find it extremely rare when the 40 db range
is not enough for the close in stuff. Even in the recent 160 CW
contests, I could not find any problem signals when listening to
Europeans on 160 in the presense of strong USA signals.
Carl Moreschi N4PY
Franklinton, North Carolina
n4py@earthlink.net
----- Original Message -----
From: "George, W5YR" <w5yr@att.net>
To: "Carl Moreschi" <n4py@earthlink.net>
Cc: "tentec reflector" <tentec@contesting.com>
Sent: Friday, March 15, 2002 4:48 PM
Subject: Re: [TenTec] Carl, Pmni, 756 etc
> Carl, just one question:
>
> Does the 340 have a DSP dynamic range of only 40 db? Or is that a typo?
>
> The PRO uses 24-bit AD/DA data which yields a theoretical 6*24 = 144 db
> overall range. Toss out the LSB in dither and noise and you are left with
> 138 db of digital dynamic range.
>
> Is this the figure you intended instead of "40 db?"
>
> A 40 db range corresponds to an effective data sample length of about six
> bits . . .
>
> 73/72/oo, George W5YR - the Yellow Rose of Texas
> Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
> Amateur Radio W5YR, in the 56th year and it just keeps getting better!
> QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
> Icom IC-756PRO #02121 Kachina 505 DSP #91900556 Icom IC-765 #02437
>
> All outgoing email virus-checked by Norton Anti-Virus 2002
>
>
> Carl Moreschi wrote:
>
> > That said, if your are inside the roofing filter, you are obviously
> > limited to the dynamic range of the DSP chip. This is 40 db. So
> > for signals that are closer than 10 khz to the desired signal, 40 db
> > is all the dynamic range you have. When an undesired signal is
> > within 10 khz of the desired signal and stronger than 40 db above
> > the desired signal, the analog AGC will come up some to keep the
> > DSP processor from overloading.
>
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