[ARC5] History of Ham Mods: Opinions?

[Michael Tauson]

On Sun, Jun 15, 2008 at 3:58 PM, Dean Billing <dean at laptop4hire.com> wrote:

> I look forward to the book.  I am curious what sources you are using?

Manuals, private correspondence, the internet, Pre-Cessna A.R.C.
internal memos et al, Cessna era A.R.C. Engineering Notes, personal
experience (pilot & ham), equipment on hand, short guys named Bob,
small furry creatures from Alpha Centauri ... pretty much everywhere I
can.

Right now, I'm looking for someone or several someones to dig in at
the Smithsonian, the National Archives and probably the LOC who is
willing to do so for small quantities of Macadamia nuts & Kona coffee
rather than the unaffordable amount of money researchers tend to want
for their services.  My going there is impossible for a great number
of reasons, and there seem to be a great number of ordinances,
statutes and laws against a few of the alternatives.

> Did you gain any insight on how Dr. Drake came up with the mechanical form of the line
> of radios that became the ATA/ARA / SCR-274-N / ARC-5.

You asnswered your own question, to wit:

> compact, rugged, modular, single band sets

The Type K had to be relatively skinny to make the modular part work.
This put the RF to audio flow on the receivers from front to back in
as compact a practical design would allow with the oscillator to
output flow from back to front with a single modulator & power supply
external to save space.  In both cases, the RF was on the front panel
and was accessible for easy connection to the antenna relay via a
single wire each for transmit and receive.

Just looking at the receiver for a moment, the width was dictated by
the tuning capacitor which, in turn, lead to the 3x3 square for the
tubes & IF cans.  The tube arrangement has the RF, LO and mixer in
front with the tuning cap and the 1st IF, the if stages in the middle
with the interstage transformer in between, and the final IF can,
detector and audio in back.  Behind them is the receiver's dynamotor
under which are the audio transformer and a few power supply bits to
satisfy the receiver's requirements.  The height was that necessary to
cover everything up on top and allow space for the components
underneath and the depth was sufficient to get all that in as small a
package as was practical.  There were other possible arrangements but
this one provided the most compact package.

> when everyone else was designing large, multiband boat anchors.

Not everyone.  I have been reminded by a friend of mine that Western
Electric's RAM was pretty much the same idea and the GE RAX wasn't far
off, though its receivers were multiband.  The RAM (and the companion
GN transmitter) was only made in evaluation quantities so disappeared
into never-never land while the Type K flourished.

> Any clue as to where his ingenious insight came from?

Being one heck of a brilliant engineer comes to mind.

BEst regards,

Michael, WH7HG