Hi,
Are there any schematics for these modifications somewhere on the net?
(especially the Sherwood mods)
Henry - PA0HJA
On 2/8/2012 6:06 AM, kc9...@aol.com wrote:
Sherwood Engineering ...has a MOD for this to totally fix it. Mix
-4 $59.00
Mine has it...Mine sure is quiet.
http://www.sherweng.com/ham.html
73,
Lee
-----Original Message-----
From: Steve Wedge <w1es1...@earthlink.net>
To: Drake List <drakelist@zerobeat.net>
Sent: Tue, Feb 7, 2012 8:17 pm
Subject: [Drakelist] Late R-4C 3rd Mixer Changes
Anyone who has had a late-production R-4C has heard the hiss when
listening to a quiet band or a weak signal. Some folks say it sounds
like bacon frying (Yum!) but to me it sounds more like the "rain"
setting of one of those noise generators they sell at Brookstone that
are supposed to put you to sleep at night.
Searching through a lot of stuff, I've located two changes that do
fairly similar things on the large scale, but require differing
numbers of parts and time in which to do them.
I knew there was a Sartori mod and - sure enough - I finally found
www.archive.org and found the June 1979 issue of 73 Magazine. This is
the change I remember doing back in the '80's. I remember that it
helped quite a bit, but the receiver still was never really quiet. It
changes the LO feed from the grid of V6 to the cathode. It also adds
a series-resonant circuit at the plate to eliminate any excess 50 kHz
crud from the output. I've wondered whether or not one could hear
this but I suppose there can be products from all that crud that could
get into the audible range.
There's also another mod that's described on
http://www.zerobeat.net/drakelist/drakemod/drmod40.html that involves
fewer added parts and looks like an easier change, overall. It does
the same overall feed change in that it moves the LO feed from the
grid to the cathode, but doesn't use the resonant circuit. It also
changes the limiting diodes to 1N4148's removes some capacitors and
replaces them with either different values or jumpers. Besides
erroneously calling out pin 1 of V6 as the old connection point, it's
easy enough to follow.
Has anyone out there tried both of these changes and, if so, which one
worked better?
73 & enjoy those Drakes...
Steve Wedge, W1ES/4
Live free or die: Death is not the worst of evils.
John Stark.
All my computers have my signature with various pearls of wisdom
appended thereto.
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