Dyna FM-3 - Installation, Mounting, and Technical Description; Installation and Mounting Guidelines; Technical Description Overview

STEREOCATOR during mono reception, but this is of no
consequence.
The volume control knob actuates a push-pull Stereo-
matic/Mono switch. When the knob is pushed "IN", the
Dynatuner will switch to full separation stereo operation
when tuned to a stereo signal, and will automatically revert
to mono operation (through both channels) on mono
broadcasts. The normal position of this control is "IN".
It may occasionally be desirable to disable the Stereo-
rnatic feature, and for this, the tuner can be locked in mono
operation by pulling the volume control "OUT". This will
enable you to make monophonic recordings of stereo pro-
grams, or to eliminate spurious interference on a mono
broadcast. Sometimes a very weak station can be received
with less background interference by operating the tuner
in the mono mode. The tuner will still indicate STEREO
when you are tuned to a stereo broadcast, but in other
respects reception will be identical to a purely monophonic
tuner. This switch does not change the tuner in any obvi-
ous way-the sound level, frequency response, and distor-
tion are the same.
The volume control is used primarily to set the level of
the Dynatuner to match that of other program sources, so
that when you switch your control amplifier's inputs, they
are heard at comparable levels. Normally in this usage,
the Dynatuner's volume control will be operated at %
clockwise rotation or higher. If the tuner is used with a
basic power amplifier only, such as the Dyna Stereo 70 or
Stereo 35, then this operates as a conventional volume con-
trol for the system.
Installation
There are two audio output sockets on the Dynatuner.
The socket marked "A" on the bottom plate (the one near-
est the line cord) is the left channel output. The "B"
(outer) socket is the right channel output. The two
shielded cables supplied (or similar type up to 25 feet in
length) should be connected between these sockets and
the "Radio" input (sometimes marked FM-MPX, or
FM-AM) of the control amplifier or preamplifier. The
Dynatuner can be connected to any audio input of 100,000
ohms or higher input impedance which can accept signal
levels between one and two volts.
The Dynatuner can also be connected directly to any
basic power amplifier which has an input sensitivity of
less than 2 volts for full output. The amplifier may be
connected to the switched AC outlet on the Dynatuner,
and the volume level would be adjusted with the tuner's
volume control.
The Dynatuner's line cord should be plugged into an
AC receptacle furnishing 120 volts of 60 cycle current (120
or 240 volts at 50 or 60 cycles with the PB-012 optional
power transformer).
Antennas
Every FM tuner requires an antenna. For some metro-
politan area use, a twin lead folded dipole is adequate for
local station reception. Instructions for making one from
the flat wire included with the kit are given in a later sec-
tion of this manual. The television type known as "rabbit
ears" is also suitable if fully extended. Either of these
antennae should be rotated for best reception, and their
most favorable orientation may vary with different stations.
The normal antenna lead-in wire is 300 ohm twin lead,
similar to that supplied with the kit. The two leads should
be connected to the two outermost antenna screw terminals,
4
leaving the center terminal unconnected. In difficult recep-
tion areas, it is sometimes necessary to use coaxial cable
for the antenna lead-in. The Dynatuner has provision for
using 75 ohm coaxial cable by connecting the shield of the
cable to the center antenna screw terminal, and the center
conductor of the cable to either of the outer screw terminals
(but not both).
An outdoor FM antenna is always better than an indoor
one, particularly if reception is desired over long distances.
Stereo reception is also more critical of antennae than
comparable mono results. High gain antenna arrays are
available for fringe area reception. These are preferable to
the "omni-directional" or "non-directional" type, but
should preferably be used with a rotator. Your dealer can
advise you on the use of these antennae, or you can write
to antenna manufacturers for detailed information.
You should realize that when difficult reception condi-
tions are encountered, improving the antenna will have far
more effective results than any other remedy, including
attempts to improve a tuner's sensitivity. The extreme
sensitivity of the Dynatuner, coupled with its exceptional
limiting action on very weak signals, may well enable you
to listen to stations you have not received before, when this
tuner is coupled with a properly designed antenna.
Mounting the Dynatuner
The Dynatuner, like all electronic devices, generates
some heat. Because the tuner has been designed with the
cover as an integral part, the unit in effect creates its own
thermal environment, and adequate allowance has been
made in the design for this normal temperature rise. Its
heat is equivalent to a 60 watt light bulb and, therefore,
adequate ventilation is required. There should be a mini-
mum of three inches of air above and behind the Dyna-
tuner. Never put anything on top of the case while the
tuner is operating. When stacked with the Dyna PAS pre-
amplifier, the tuner must be installed above the preampli-
fier. The preamplifier does not require ventilation. The
tuner cannot be stacked above the Dyna SCA-35 amplifier.
When mounting the Dynatuner in a panel or cabinet,
consideration must be given to adequate air flow, particu-
larly if other heat-producing devices, such as amplifiers,
are also in the same area. In restricted space, and particu-
larly
if the tuner must be mounted face up, it is essential
that a small circulating fan be used. The warranty on the
Dynatuner is void if it has been abused through inadequate
ventilation.
It is simple to install the Dynatuner in any panel up to
l" in thickness. A supporting shelf should be installed flush
with the bottom of a 13Y16" x 3l~G" cutout, and the rubber
feet are not used. A PBK bracket kit is available from
Dynaco for $2, which takes the place of the shelf. No
C.O.D.s please. If it is desired to mount the Dynatuner
and the Dyna PAS-3 in a single cutout, the rubber feet are
used on the· tuner, which is mounted above the preamp,
and the cutout should be made 7
J
0/16" high by 13YJl' wide.
TECHNICAL DESCRIPTION
The circuit features which distinguish the FM-3 can be
described only in somewhat technical terms. Those not
interested in the technology may ignore this section.
The FM-3 has the following basic tube and circuit se-
quence:
1. A cathode coupled tuned R.F. amplifier using a
6AQ8/ECC-85 dual high frequency triode.