Among us kids who were licensed as teens in the mid 50's, the Q
multiplier was a hot item. Most of us could not afford the latest
and greatest receivers so the Heathkit Q-Multiplier was a desired
accessory . I believe is could also do a notching function. I never
had the Heath version myself, but many friends did. I had a
Hammarlund HQ-100 immediately upon its introduction and as far as I
can recall that was the first commercial radio to have a Q-Multiplier
built in as opposed to an add-on accessory. More expensive radios had
crystal filters and the Cadillac of the era, the Collins 75A4 had
mechanical filters. The $500 price tag of the 75A4 put it in the
"dream-on" category to those of us who only had part-time jobs or in
my case (I was 13 when licensed) too young to even work at anything
legally. It actually was pretty effective once you got to learn how to
use it. As I remember it was far more effective on CW than phone
(which was still heavily standard full carrier AM phone.) The
Hammarlund version only had a "peak"
function. I believe the Heathkit version's notch function could
be used for reducing heterodyne squeals although I have very
liitle experience with that. I believe the Heath also had a
third function, but I don't remember what it was.

Jon W3JT



On Tue, 10 Apr 2007 08:32:51 -0700, Dick wrote:

On 10 Apr 2007 04:11:25 GMT, (Michael Black)
wrote:

pltrgyst ) writes:
On 9 Apr 2007 18:53:01 GMT, (Michael Black) wrote:

A Q-multiplier is a regenerative stage.

It's prime was in the days of the 455KHz IF, where the improved selectivity
would actually make a difference. At a higher frequency, it would still
increase the selectivity of the tuned circuit, but not enough to narrow
the passband for voice or CW.

So what about audio Q-multipliers? Do they function on the same principle?

-- Larry

Originally yes, though I've seen "audio Q-multipliers" described in
construction articles that are more strictly average audio filters.

They may even come out of the same place. The selectoject was described
in QST in the late forties, by O. G. Villard, and it uses the principle
of regneration to get better selectivity at audio. And O. G. Villard is
the name I'd associate with the use of the Q-Multiplier for better
reception of AM (there are references to a QST article by him on that topic
in an early ARRL SSB manual). But I've never seen a specific link between
the selectoject and the Q-Multiplier at the IF of a receiver, so I don't know
if he came up with the IF Q-multiplier as we know it, or someone else did.
Certainly O. G. Villard, who died only three years ago, came up with
quite a few things important to amateur radio, including a lot of work
in SSB in the early days.

Michael VE2BVW


Interestingly, this month's QST in the 50 Years Ago column lists a
variable band width Q-Multiplier by Ronald Ives (April 1957.) The
article references the original Villard article in the April 1952
issue of "Electronics" magazine.

Dick - W6CCD