On 06/10/13 13:28, Jimbo... wrote:
"FranK Turner-Smith G3VKI" wrote in message
...
"Jimbo..." wrote in message
...

"To boot" seems quite apt for you, old Bean.

Gareth would turn the other cheek, but it's hard to do that when a
copper's
got your head pinned to the floor with his size 12 standard issue.


probably one of the last few things he did before he topped
himself...............

The fact that the plods videoed the arrest tells me that they were
expecting, and got, problems.
More recent allegations of attacking postmen etc confirm their need for
caution.
That plod had no need to top himself over an incident in which he lost his
cool while dealing with an idiot. He had been acquitted and IMHO should
have brought counter-charges for defamation.
;-)
.
73 de Frank Turner-Smith G3VKI - mine's a pint.

I blame the freemasons in the polis.......


Not the RSGB?

--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.co.uk
..
Ubuntu 12.04
Thunderbirds are go.

"gareth" wrote in message
...
I wonder if anyone can offer a picture of the variable
selectivity arrangement of
the Eddystone EA12, which I believe was also used by some
other manufacturers?

This was the scheme whereby coupling between the primary
and secondary of IF
transformers was varied nechanically by distancing the two
halves of the transformer
from each other.

I have access to photos showing the operating levers, but
what interests me for
the moment is to have a peek, or peeks, inside the IF cans
themselves.


This is the same arrangement used by Hammarlund in the
Super-Pro series. Its been too long since I had a Super-Pro
IF can open to remember exactly how the movable coils were
fastened and guided but the variation was done by a post
coming out the bottom of the can and operated by a cam on a
shaft turned by the front panel "selectivity" knob. Very
simple mechanism. This type of variable selectivity is the
only one with completely symmetrical expansion of the
passband. Those using tapped inductances coupled to the IF
coils, such as used in the SP-600-JX and RCA AR-88, are
nearly as good. Capacitance coupling usually results in
some asymmetry as seen in some Hallicrafters receivers
although the variable pass band in the SX-28 works quite
well.
Later in this thread someone asks about variable
crystal filters. There are essentially two forms: the
original Lamb filter and the later one patented by
Hammarlund in 1938 and first used in the HQ-120-X. The
Hammarlund filter has the advantage that the center
frequency does not vary with the bandwidth adjustment or
when the phasing null is moved around. The Hammarlund
circuit was used in the SP-200, 400 and 600 Super Pro
receivers as well as the HQ series and, in slightly modified
form, by TMC in the GPR-90 and by Collins in the 75A-1,2,3
and 51J series. National and Hallicrafters mostly used the
earlier Lamb circuit. as did Hammarlund in the SP-100
Super-Pro.


--

--
Richard Knoppow
Los Angeles
WB6KBL

WOW!

A very full response, thank-you.


"Richard Knoppow" wrote in message
...

"gareth" wrote in message
...
I wonder if anyone can offer a picture of the variable selectivity
arrangement of
the Eddystone EA12, which I believe was also used by some other
manufacturers?

This was the scheme whereby coupling between the primary and secondary
of IF
transformers was varied nechanically by distancing the two halves of the
transformer
from each other.

I have access to photos showing the operating levers, but what interests
me for
the moment is to have a peek, or peeks, inside the IF cans themselves.


This is the same arrangement used by Hammarlund in the Super-Pro
series. Its been too long since I had a Super-Pro IF can open to remember
exactly how the movable coils were fastened and guided but the variation
was done by a post coming out the bottom of the can and operated by a cam
on a shaft turned by the front panel "selectivity" knob. Very simple
mechanism. This type of variable selectivity is the only one with
completely symmetrical expansion of the passband. Those using tapped
inductances coupled to the IF coils, such as used in the SP-600-JX and RCA
AR-88, are nearly as good. Capacitance coupling usually results in some
asymmetry as seen in some Hallicrafters receivers although the variable
pass band in the SX-28 works quite well.
Later in this thread someone asks about variable crystal filters.
There are essentially two forms: the original Lamb filter and the later
one patented by Hammarlund in 1938 and first used in the HQ-120-X. The
Hammarlund filter has the advantage that the center frequency does not
vary with the bandwidth adjustment or when the phasing null is moved
around. The Hammarlund circuit was used in the SP-200, 400 and 600 Super
Pro receivers as well as the HQ series and, in slightly modified form, by
TMC in the GPR-90 and by Collins in the 75A-1,2,3 and 51J series.
National and Hallicrafters mostly used the earlier Lamb circuit. as did
Hammarlund in the SP-100 Super-Pro.


--

--
Richard Knoppow
Los Angeles
WB6KBL

"gareth" wrote in message
...
WOW!

A very full response, thank-you.


Let's go Beanie, let's go.

"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.

"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.