Specifications

if he could have heard FM the way we heard it over the
Mac MR 78.
There was only one instance where we found it necessary
to use the SUPER-NARROW position of the selector switch,
and that was when we were trying to listen to a weak sig-
nal originating some 120 miles from our listening location
— one nestled between a stronger signal 200 kHz below it,
and a much stronger local station, 200 kHz on the higher
side of the dial. If you've ever tried to receive that kind
of signal on a lesser tuner, you'll know what we mean. In
any case, when we did switch to the SUPER-NARROW
position, we actually were able to listen to the desired
distant station and distortion, though audibly higher,
was still at tolerable levels.
FREQUENCY - HZ
Mono: (1) Total Harmonic Distortion (THD)
Stereo: (2) Total Harmonic Distortion (THD)
Fig. 9 - Separation and distortion versus frequency
(with selectivity switch set to "NARROW")
Previously, we had measured signal voltages of 2 to 3 volts
at that location and found that most tuners did exhibit
cross-modulation and other overload effects. With the
"Mac" tuner, we were able to clearly separate closely
spaced high-signal stations on the dial with nary a trace of
interference from other strong-signal stations in the same
vicinity.
Other Use and Listening Tests
Back in our lab (some 20 miles from the city), we began
to appreciate the importance of that selectivity switch on
the front panel. If you are an inveterate FM DX-er, you will
be amazed (as we were) at how many signals you can separ-
ate and receive clearly by using the narrow (and at times
even the super-narrow) selectivity switch positions on the
MR 78. Here is a tuner that doesn't compromise between
low distortion and wide bandwidth. 55 dB of selectivity
(that claimed in the NORMAL setting) is no problem if you
are not plagued by adjacent and alternate channel signals.
In fact, the normal setting, coupled with those linear phase
filters in the IF section, rendered the kind of reception
from the few good quality stations that we have in our lis-
tening area that we had often dreamed about- Program
quality varied, of course, but when we were fortunate
enough to tune to a live concert (yes, we still do have some
live FM programming in this area, albeit at midnight each
night), the results were truly astounding. We had the feel-
ing that the late Major Armstrong, too, would have smiled
31
FREQUENCY- HZ
Mono: (1) Total Harmonic Distortion (THD)
Stereo (2) Total Harmonic Distortion (THD)
Fig. 8 — Separtion and distortion versus frequency
(with selectivity switch set to "NORMAL")