Richard Knoppow wrote:
"k3hvg" wrote in message
. ..
BTW, I wonder if anyone out there has had experience
with the Hallicrafters version of the SP-600? I am
curious how its performance compares with the original.


If my info infers what I believe it does, the R-274 (nee
SX-73) was the first of the line. The Hammarlund
SP-600/R-274( ) came later as they beat out Hallicrafters
for the follow-on contracts. I have both receivers but
prefer the Hallicrafters. Tuning is much smoother and the
SX-73 has all the normal features of a general coverage
receiver. I do not, however, have a clue as how they
stack up regarding responses. I have heard rumors that
there was a Hallicrafters R-274 "B" version of but the
contract number is the same as the "original" R-274. I
suspect this was merely a simple production change of a
couple of components (capacitors) rather that a
substantive design change.
de K3HVG


It would be interesting to see when the Hallicrafters
project began. The Hammarlund SP-600 was first announced in
1948 but the advertizing features a drawing of what was
probably either a mock-up or prototype. Also, the details in
the ads vary in important ways from the production receiver.
The first SP-600's came out about 1950. I think some of the
changes were due to Hammarlund's realizing that the main
customer would be the military. I am not sure of the date of
the SX-73. The SX-73 is not a clone of the SP-600. Its a
different design in many respects but meant to meet the same
purchasing specs.
As far as the dial etc., a properly working SP-600 has
one of the smoothest tuning mechanisms around. Hallicrafters
may be as good but the SP-600 is so good that its unlikely a
different design would be significantly better. I also don't
know what you mean by "normal features". Both receivers have
about the same features and there is nothing missing from
the SP-600.


Truth told, you're about right..... The SP-600 does have virtually the
same features. I'd forgotten that the '600 does have a filter phasing
control. I guess the only feature might be the antenna tune control but
one could argue the efficacy of that! The only other thing might be the
physical compression/calibration of the amateur bands. The
Hallicrafters has a bit more spread than the SP-600 on most ham bands.
Beyond that, your comment is appropriate.

The other comment might be that re-capping an early SP-600 can be
laborious, especially when replacing the caps on the turret modules and
inside the RF side channel. Not difficult, just laborious. Later
models don't have that issue, of course.