"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