I have added external DSP units to help noise. One particular rig I have
with dual receivers I have one on each channel. It has made the difference
between Q or no Q. Just a suggestion from here.
73, Mike WA5POK
--------------------------------------------------
From: "Don Jones" <k...@comcast.net>
Sent: Wednesday, February 02, 2011 12:01 PM
To: <drakelist@zerobeat.net>
Subject: [Drakelist] R-4C Noise Blankers,Dynamic Range & roofing filter
mod's
I agree, when using the 8kHz Drake Roofing filter the 4NB noise blanker
will
clean-up some interfering noise sources. But only some of the time. I
(and
many others who have e-mail me privately) have found that you get better
noise reduction by reducing the IF BW's. This would include going to a
600Hz
roofing filter making the 4NB ineffective - but more importantly - NOT
NEEDED.
I look at a "hot-rod Sherwood R-4C receiver" as a utilitarian tool used to
dig deep down into the noise floor and root out S Unit 0 weak signal DX
stations buried in the midst of QRM.
I did not completely buy into the "wild claims" of the users of these
Sherwood R-4C's until I actually used one. All I can say is, "Holy Cow!" I
am now a "convert" of the writings W8JI regarding the R-4C in its
un-modified state. This "Holy Cow" is based upon side by side comparisons
to
a stock Drake R-4C to a Sherwood R-4C. Basically all you get is the
receiver
performance from a FT101B/E, the only advantage R-4C has is the passband
(IF
Shift) tuning.
Conversely if one is rag chewing on SSB with 3kHz wide "Hi-Fi SSB" (or
worse
yet AM), they generally are not concerned about digging out weak CW
signals
that are S-0 on the S meter. These users typically are happy campers with
a
75M 20+dB over S-9 QSO while running 1.5kW (or more) for a "in-state rag
chew." They remain happy campers until someone moves in 2kHz away and is
running similar power. But at least their 4NB noise blanker's work...
BTW, the measured 2kHz Spacing Dynamic Range of a TR-4C is 68dB which is
10dB better than the stock R-4C. Plus the 180W output of the TR-4C will
drive a GG 4-1000A amplifier with 3500Vdc B+ to 2,300W-rms out on 75M SSB.
73 es Gud DX,
Don Jones KO7i
Arlington, WA
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