Specifications

THE MOST FLEXIBLE CONTROL SYSTEM
EVER FOR A DIGITAL DISPLAY
PROFESSIONAL FM TUNER
The Mclntosh MR 80
Engineering direction dictated a tuner design
governed by insistence on great flexibility and ease
of use. This had to be done while designing for great
sensitivity and the world's best selectivity in keep-
ing with the needs of low distortion. These values
were achieved. They retain the Mclntosh reputation
for outstanding performance, long life and reliabili-
ty.
To assure long term trouble free operation, tuning
a station on the MR 80 is achieved electronically.
The MR 80 can be tuned four different ways:
1. Manual tuning by rotating the main tuning knob
2. Auto Scan automatically searches for the next
available station up or down the dial
3. Presets allow you to select the four most listened
to stations at the touch of your finger tip
4. Remote Scanning will allow the MR 80 to be tuned
to a station from a wired remote location.
Two separate antenna systems can be connected
to the MR 80: 1) An outdoor or indoor FM antenna, or
2) a cable from your local cable company. The anten-
na selection is controlled by an electronic switching
device.
The MR 80 uses electronic varactor tuning instead
of the more conventional mechanically ganged var-
iable tuning capacitors. Variable tuning capacitors
can with age collect dust and dirt, reducing their per-
formance. Mclntosh uses double varactor diodes to
provide the necessary tracking between the dif-
ferent tuned RF stages. When a weak distant station
is adjacent to a strong local station the Preselector
switch will add in an additional tuned circuit pro-
viding an extra degree of selectivity to reduce the in-
terference from the adjacent strong station.
After the RF amplifier two paralled tuned circuits
are used to provide the proper load impedance for
the bipolar transistor. These two tuned circuits
greatly improve the image rejection and overload
performance of the tuner, as well as increasing the
RF selectivity.
An innovative new lock circuit was developed for
use in the MR 80. This new circuit allows correct tun-
ing without the use of a center tune meter. The MR
80 will be correctly tuned regardless of the stations
transmitted signal as related to its assigned fre-
quency. Two operational amplifiers cause the lock
circuit to track a station even if it drifts 1 MHZ.
The mixer is a balanced matched dual J-FET and
bipolar transistor circuit.
After the mixer the signal is electronically switch-
ed to go either directly to the IF amplifier or to go
through a quartz crystal filter. The MR 80 has the nar-
rowest IF bandwidth ever used in a stereo tuner. It is
the correct width to let just one FM station through.
The excellent selectivity of the MR 80 (210 kHz wide
at 60 dB down) permits tuning stations that are im-
possible to receive on ordinary tuners.
The SUPER NARROW selectivity position adds a 4
pole - 4 zero crystal filter to the other 5 IF filters.
SUPER NARROW permits listening to stations not
heard with most other FM tuners. The 5 stages of IF
amplification provide the necessary gain to reduce
noise in the signal and the interference from other
stations. They are piezoelectric fixed frequency
filters in place of normal tuned circuits. An advan-
tage the IF stages will always stay in alignment,
even with age.
The signal strength indicator column is the sum of
all IF stages instead of just one it indicates the
signal strength throughout the entire IF system.
The selectivity section of the IF amplifier is the
LIMITER with a total gain of 80 dB. The use of very
high gain in the limiter circuit produces hard limiting
with very good impulse noise rejection. Limiter
bandwidth is greater than 50 MHz, producing ex-
cellent detector capture characteristics.
A broadband Foster-Seeley discriminator is used
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