National NC 300 information

[George Maier]

Hi all:
I'm currently on my third NC-300, and have had a 303 also.  All of the
comments so far have been dead center with respect to the RF gain and the ER
mods.  From personal experience, I don't recommend the L-C filter mod (20 Hy
choke & 700Pf cap) between the audio driver and the audio output - too much
chance for hum pick-up that you can't get rid of.
In addition to the mods that K0EEO suggests in the ER article, get your
hands on an NC-303 schematic and rebuild the NC-300 audio output to look the
same.  It requires an added filter cap and a few new 150 Ohm resistors. The
NC-303 deals with some of the distortion issues by adding feedback from the
audio output to the driver, and by separating the screen B+ supply from the
plate supply. This takes care of most of the problems the the L-C filter mod
tried to address.
Also, I haven't tried it yet, but I believe that the value of C55 could be
optimized for better IF to product detector voltage ratios.  I think
dropping it to - maybe 3 pf would be a start.
Finally - a moment of reflection for Ed Harrington, W1JEL, whe recently
became a silent key.  Ed was the circuit designer for the NC-300, and a good
friend of mine.  He was a real gentleman, and always enjoyed talking about
the 300.
73 to all
George Maier - K1GXT


-----Original Message-----
From: Boat Anchor Owners and Collectors List
[mailto:BOATANCHORS at LISTSERV.TEMPE.GOV]On Behalf Of Larry Knapp
Sent: Tuesday, November 19, 2002 11:14 AM
To: BOATANCHORS at LISTSERV.TEMPE.GOV
Subject: National NC 300 information


To all - Electric Radio magazine is a great resource for information on
these
lovable old receivers...the index to past issues lists two references to
updates or "perhaps" mods to the NC-300....these are:
    March 92, Issue #35, page 11
September 92, Issue #41, page 16

There is a review of the NC-300 in October 1990, Issue #18, page 15.

Whether the NC-303/NC-300 are compatable or not, I don't know.  I have a
NC-303.  In Electric Radio, there was a reference to a modification that
would
improve SSB reception, which I did to my NC-303.  If this also "could" be
used
on a NC-300, I do not know.  The reference is:
October 1992, Issue #42, Page 18.

73, Larry KC8JX

=====
May your days be full of sunshine and good thoughts fill your head.
From: Larry Knapp, KC8JX, St. Joseph, Mi  49085
  Best 73's

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