"Hank" wrote in message
...
In article
,
Richard Knoppow wrote:

James Millen was one of the founders of National but
eventually was pushed out of the company. He started his
own
company, also in Malden Mass, and probably made many parts
for National as well as his own stuff. Millen made very
high
quality components.

Millen Mfg., at least at the time I worked there, was in
direct
competition with National Co. on several products, and
neither
company supplied the other.

The National HRO was a revolutionary receiver in its
day
and stayed one of the favorites for both ham and
commercial
use for some thirty years. The mechanical design is
attributed mostly to James Millen and the electronic
design
mostly to Herbert Hoover Jr., son of the president of the
US.

While the HRO was a legendary product, I'd hardly call it
"revolutionary." It was a follow-on to the AGS line, with
objectives
to maintain AGS performance at lower cost-to-manufacture,
and to
normalize the coil-set interface so that the tuning coils
could be
built all-in-one-box and interchangeable. An examination
of the
schematic will show it to be essentially a copy of
higher-end home
entertainment circuits of the era, with a crystal filter
and bfo
added. Much of the actual performance came from use of
better coils
(house-built) in the RF and IF stages, a house-built
tuning capacitor,
and the house-built tuning dial was superior to almost
anything else
around. In short, a relatively straightforward
tried-and-proven
electrical design, but extremely well-executed in
component quality
and mechanical structure, pretty much hallmarks of Jim
Millen's team.

Worth noting that the NC-100, National's follow-on
product, had
similar performance, with the advantage of having
internally-mounted
and switchable tuning coils.

Hank

While the HRO had similar circuits to home receivers of
the time I rather think there was not that much variation
available. The HRO did use pentode mixers in place of
hexode or pentagrid mixers resulting in low noise. The
NC-100 was certainly a clever design but had only one RF so
its image rejection is not as good as the HRO.
I forgot to mention Dana Bacon another designer at
National. I am not sure what contributions he made.


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Richard Knoppow
Los Angeles
WB6KBL