"gareth" wrote in message
...
WOW!

A very full response, thank-you.


After I posted this I realized that I forgot a part. In
the Super-Pro there is a phenolic lever between the rotating
cam and the rods from the movable coils. I am not sure why
the rods are not moved directly by the cams. I think
Hammarlund had a patent on the IF variation system but I
don't have the number. The Hammarlund crystal filter is
described in _QST_ Dec 1938, p.33 D.K. Oram "Full Range
Selectivity with the 455 khc Crystal Filter" Oram's patent
is USP 2222043 You can get patents by number from the U.S.
Patent and Trade Mark Office or from Google Patents. The
Google site has the advantage that patents are searchable by
text for _all_ dates and are available in PDF form.
I also have the Lamb patents but it will take some
searching since my file is organized by patent number and
not title. However, they are easily found by doing a Google
search for James Lamb. You will also find his patent for
the famous Lamb Noise Blanker. Lamb had more than one patent
on crystal filters and wrote extensively about them in the
early thirties editions of QST. AFAIK, the first application
of the Lamb filter was in the HRO. The first Hammarlund
filter was in the HQ-120-X and it was later applied to the
Super-Pro. Some Series 100 Super-Pros have crystal filters
as an add-on but these are not the later version. BTW, the
Lamb patent was licensed to James Millen. At the time he was
one of the principles of the National Radio company and is
supposed to have been responsible for the mechanical design
of the HRO.


--

--
Richard Knoppow
Los Angeles
WB6KBL

Further information most welcome, thank-you

In the 1948 Radio handbook which I mentioned previously, there are adverts
from a company by the name of Millen, and I assumed it was the same guy
after he had left National.

Your comment about a phenolic intersperser is no doubt some means of
isolating an
earthy contact?

It would be interesting to know from the Lamb patent whether he proposed
therein the
technique of Single Signal Reception by the use of the phasing control to
null
out the audio image, or whether this was something that came about through
experience?


"Richard Knoppow" wrote in message
m...

"gareth" wrote in message
...
WOW!

A very full response, thank-you.


After I posted this I realized that I forgot a part. In the Super-Pro
there is a phenolic lever between the rotating cam and the rods from the
movable coils. I am not sure why the rods are not moved directly by the
cams. I think Hammarlund had a patent on the IF variation system but I
don't have the number. The Hammarlund crystal filter is described in _QST_
Dec 1938, p.33 D.K. Oram "Full Range Selectivity with the 455 khc Crystal
Filter" Oram's patent is USP 2222043 You can get patents by number from
the U.S. Patent and Trade Mark Office or from Google Patents. The Google
site has the advantage that patents are searchable by text for _all_ dates
and are available in PDF form.
I also have the Lamb patents but it will take some searching since my
file is organized by patent number and not title. However, they are easily
found by doing a Google search for James Lamb. You will also find his
patent for the famous Lamb Noise Blanker. Lamb had more than one patent on
crystal filters and wrote extensively about them in the early thirties
editions of QST. AFAIK, the first application of the Lamb filter was in
the HRO. The first Hammarlund filter was in the HQ-120-X and it was later
applied to the Super-Pro. Some Series 100 Super-Pros have crystal filters
as an add-on but these are not the later version. BTW, the Lamb patent
was licensed to James Millen. At the time he was one of the principles of
the National Radio company and is supposed to have been responsible for
the mechanical design of the HRO.


--

--
Richard Knoppow
Los Angeles
WB6KBL

"gareth" wrote in message
...
Further information most welcome, thank-you

In the 1948 Radio handbook which I mentioned previously,
there are adverts
from a company by the name of Millen, and I assumed it was
the same guy
after he had left National.

Your comment about a phenolic intersperser is no doubt
some means of isolating an
earthy contact?

It would be interesting to know from the Lamb patent
whether he proposed therein the
technique of Single Signal Reception by the use of the
phasing control to null
out the audio image, or whether this was something that
came about through experience?


I think this was part of Lamb's original intention. The
articles originally describing the use of the filter were
aimed at "single signal" reception, meaning that the audio
image was suppressed. The Lamb filter required some juggling
between the bandwidth and phasing adjustments to get the
response to where the operator wanted it since they
interacted with each other and with the center frequency.
Nonetheless, the filter worked very well and provided an
order of magnitude better selectivity than was available
previously.
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. There is considerable history of both
National and Millen, including a Millen Society, on the web,
a Google search will find it.
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.


--

--
Richard Knoppow
Los Angeles
WB6KBL

"Richard Knoppow" wrote in message
...
"gareth" wrote in message
...
Further information most welcome, thank-you
In the 1948 Radio handbook which I mentioned previously, there are
adverts
from a company by the name of Millen, and I assumed it was the same guy
after he had left National.
Your comment about a phenolic intersperser is no doubt some means of
isolating an
earthy contact?
It would be interesting to know from the Lamb patent whether he proposed
therein the
technique of Single Signal Reception by the use of the phasing control to
null
out the audio image, or whether this was something that came about
through experience?

I think this was part of Lamb's original intention. The articles
originally describing the use of the filter were aimed at "single signal"
reception, meaning that the audio image was suppressed. The Lamb filter
required some juggling between the bandwidth and phasing adjustments to
get the response to where the operator wanted it since they interacted
with each other and with the center frequency. Nonetheless, the filter
worked very well and provided an order of magnitude better selectivity
than was available previously.
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. There is considerable history
of both National and Millen, including a Millen Society, on the web, a
Google search will find it.
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.


I'm in the process of making a retro RX, primarily because I've a junk box
going back
50 years and if I don't do something with the bits now, then the executor of
my will
is likely to skip the lot.

I recently analysed the Sperry PWD dial from the HRO, and conceived of a way
to
reproduce it, but without needing an internal toother ring.

However, my tastes have changed, and I'm now heading for an RX that is
similar in style
to the Eddystone EA12.

But the one thing that I owe to the National design in my musings is the
possibility of
emulating the Catacomb from the NC100X RX, as the means of simplifying the
wiring
of a bandswitch.

I was originally interested in the variable selectivity of the Eddystone,
and, indeed, have obtained
a photo of the innards of one of the variable IF transformers, but I think
that I'll do a coouple of ladder
filters based on modern practice, with both SSB and CW versions.

Once again, very interesting articles from you, thanks!

Gareth G4SDW

"gareth" wrote in message
...
I'm in the process of making a retro RX, primarily because I've a junk box
going back
50 years and if I don't do something with the bits now, then the executor
of my will is likely to skip the lot.

I recently analysed the Sperry PWD dial from the HRO, and conceived of a
way to reproduce it, but without needing an internal toother ring.

However, my tastes have changed, and I'm now heading for an RX that is
similar in style to the Eddystone EA12.

But the one thing that I owe to the National design in my musings is the
possibility of
emulating the Catacomb from the NC100X RX, as the means of simplifying the
wiring of a bandswitch.

I was originally interested in the variable selectivity of the Eddystone,
and, indeed, have obtained
a photo of the innards of one of the variable IF transformers, but I think
that I'll do a coouple of ladder
filters based on modern practice, with both SSB and CW versions.

Once again, very interesting articles from you, thanks!

Gareth G4SDW

Let's go Beanie, let's go.

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

"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.


--

--
Richard Knoppow
Los Angeles
WB6KBL

On Mon, 14 Oct 2013, Richard Knoppow wrote:


"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.

And that the HRO had two RF stages seems to be a significant factor.

Even in the seventies, when Ray Moore wrote a number of articles about
receiver design in Ham Radio magazine, he pointed out that one reason the
HRO stood out was the 2 rf stages, which mean much better image rejection
than the average receiver. The HRO-60 (or was it the 50?) added double
conversion on the higher bands, but the earlier models were still
contenders in that period for good image rejection on the higher bands.
And of course, the design was good, so the extra stage actually helped
rather than hindered.

A superhet is a superhet, it's small details like this that made some
better than others.

A couple of years ago, I found at a garage sale for 2.00 a Grundig/Eton
pocket shortwave receiver. It's a pretty crummy receiver, but without
adding cost to it, they included a frequency counter. So a receiver
probably as bad and as simple as my Hallicrafters S-120A from 1971
instantly gets a giant improvement in tuning because of that frequency
counter. And once they did away with the analog dial, they could break
the tuning segments up into smaller ranges, helping the tuning process.

What initially complicates the receiver tremendously (or would if the
frequency counter wasn't a single IC that also included a clock function
and cost very little and took up little space), actually simplifies it.

Today, you can stick with a 455KHz IF and then fuss over image rejection,
or you can move to a higher IF and simplify the front end. Or go with
double conversion, getting the easier image rejection, yet selectivity
down where you can do things like use LC circuits.

A single conversion receiver with 455KHz and one RF stage (if that) can't
be much different from a circa 1930s receiver, communication or consumer,
but you can now make simple receivers with other methods that actually
mean better performance.

It amazes me that over the past 7 years or so I've found shortwave
receivers at rummage and garage sales, all nice and cheap, that are so
much better than that 1971 Hallicrafters. Or even buy a new digitally
tuned portable receiver for about the price I paid in 1971 for that
Hallicrafters, and get nearly infinitely better capability.

Michael VE2BVW

On Sun, 13 Oct 2013, Richard Knoppow wrote:


"gareth" wrote in message
...
Further information most welcome, thank-you

In the 1948 Radio handbook which I mentioned previously,
there are adverts
from a company by the name of Millen, and I assumed it was
the same guy
after he had left National.

Your comment about a phenolic intersperser is no doubt
some means of isolating an
earthy contact?

It would be interesting to know from the Lamb patent
whether he proposed therein the
technique of Single Signal Reception by the use of the
phasing control to null
out the audio image, or whether this was something that
came about through experience?


I think this was part of Lamb's original intention. The
articles originally describing the use of the filter were
aimed at "single signal" reception, meaning that the audio
image was suppressed. The Lamb filter required some juggling
between the bandwidth and phasing adjustments to get the
response to where the operator wanted it since they
interacted with each other and with the center frequency.
Nonetheless, the filter worked very well and provided an
order of magnitude better selectivity than was available
previously.
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. There is considerable history of both
National and Millen, including a Millen Society, on the web,
a Google search will find it.
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.

And Hoover Jr. was president of the ARRL for a while.

Michael VE2BVW

"gareth" wrote in message
...
Further information most welcome, thank-you

In the 1948 Radio handbook which I mentioned previously, there are adverts
from a company by the name of Millen, and I assumed it was the same guy
after he had left National.

Your comment about a phenolic intersperser is no doubt some means of
isolating an
earthy contact?

It would be interesting to know from the Lamb patent whether he proposed
therein the
technique of Single Signal Reception by the use of the phasing control to
null
out the audio image, or whether this was something that came about through
experience?

Let's go Beanie, let's go.