You may wish to consider the following:
Solid state mixer mod: The 6EQ7 (I believe) is notoriously prone to
microphonics and earlier I had purchased several spare tubes just for this
reason. They were hard to get then. They did not last long, so this mod
essentially solved the problem and resulted in a much quieter unit.
Solid state product detector: The original product detector was a simple and
poor design originating to the R blank line; this fixes the unit and makes
the detection more robust and less prone to producing noise.
Solid state power supply and capacitor kit (actually 2 kits here): many of
the mods need a clean and regulated source of DC power. This mod replaces
the original capacitors (probably in need of that any way) and PROVIDES A
NEW POWER SUPPLY for the radio. Even up to the C line, when Drake needed a
voltage less than 250 VDC, they inserted a (generally) big resistor in the
line. This was true for the few solid state devices that were in the radio
to start with. This cleans it up by providing a clean and regulated source
of DC power and allows the radio to run at less DC current on the power
supply. Less current, less heat and less wear on the power transformer.
The best thing you can do for the radio and the modification that wakes up
an otherwise lethargic radio is the 600 Cy roofing filter in the first IF.
This is the first application (that I know of) of the roofing filter concept
for improved CW operation. It is an amazing modification and turns an ok
radio into a sprinter. By measurement, the modified R4C has a 2 KC dynamic
range of in the 80 dB range. Up until 15 years ago this was a measurement
not worth doing as no radio could perform in that regard. You simply
accepted what the manufacturer, any, gave you . It took an otherwise good
radio and made it a champ. As I work DX only, it made working a pile up or
a contest a pleasure instead of a chore. It is truly amazing and
essentially is what put Sherwood on the radio map. Incidentally, it was
Bob's poor showing using a pair of new R4Cs on the ARRL 160M CW contest that
gave birth to the first roofing filter. Since the intro of this mod, the
other manufacturers have copied it and offer it in their new designs. It
all began here with the R4C mod that Bob Sherwood did in the 60's. The
articles in Ham Radio where they were first published are considered
classics. If you do but one of the modifications, do this one.
Lastly, the audio amplifier tube and circuit can be replaced with a solid
state unit. It provides cleaner audio and reduces the heat and current draw
even further.
The radio I have has some of the home brew items of those articles as well
as the modules purchased from Sherwood. I would recommend going the
purchase route as all of the chore of mounting and part placement is already
worked out in the radio for you.
Good luck on your adventure. You will not be sorry. There are other mods
that I have considered but not done that would incrementally improve the
radio, but do not have them. There are also some simple mods for the T4X as
well and I have used some of these as well. There are some that say that
such modifications are heresy and should not be done to keep the stable pure
and true. I do believe it is because of these mods that Drake is still
alive in the contesting field. I would rather take the pleasure of using a
modified radio than have a pristine original that I would never use.
What you will end up with is a vastly improved radio, beyond what Drake
could have imagined. It holds its on with any other radio I have ever used,
Yaesu 1000, Orion, Omni 6+ (with the IRC roofing filter), Kenwood. You get
the added smell and history and that full bodied sound that only the tube
radios have.
Keep in touch and go for it! I envy you for the great adventure you are
about to embark on!
David Assaf, III
W5XU
From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net]
On Behalf Of Steve Wedge
Sent: Friday, December 30, 2011 5:49 PM
To: AirRadio; drakelist@zerobeat.net
Subject: Re: [Drakelist] R4C Sherwood mods
Hi, Max -
I'd go for the mods that improve on the solid-state circuits. Because of
the period when these radios were made, many of the early solid-state
circuits that were used in the C's have had significant improvements -
particularly the audio chain.
I owned a couple of C-Line sets (one early and one late) and both had the
Sherwood audio amps - which I consider to be worthwhile. There was another
mod that may not have been Sherwood that involved the third mixer and
placing an RF choke there (IIRC, it was in the cathode circuit, but we're
dealing with a 25-year-old memory here...) - it applied only to the
late-production and got rid of much of the hiss in the audio.
Bear in mind that a lot of those mods turned the C-Line into contest-ready
radios, which - if you're only operating casually - will not
