Tandberg TPT 3001 A Brochure

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Technical Paper

Tuners TPT 3001A -TPT 3011A

TUNERS The new analog tuners TPT Although they are designed for cality of the reproduced sound
3001 A and TPT3011A are the different market segments This is ensured by their many
result 01 a long term develop» they do have one major com» design similarities,
ment in the Tandberg labs. mon denominator: The musi-

TP'I' 3001 A

TPT 301 1 A

The front end The front ends employ and Mixer stages. This The TPT 3001A utilizes 8
ganged. tuned circuits where achieves respectively; stable tuned circuits, the TPT 3011A.
DC voltage controlled capacir accurate tuning and excellent 5, to prevent Mirror image
tance diodes are used as tun- sensitivity combined with su- (21 4 MHz) and other out of
ing elements, and Dual-Gate perior headroom. band distortion,

MOSFETs are used in the HF
' Both tuners employ the same
Prggrammmg ingenious tuning system. P Program Signal
unit 1 2

In addition to the main tuning.
there is a second stage which
stores 8 pre-tuned FM stations
in an electronic memory,This
pre»tuning system is based on
a voltage synthesis principle
combined with a fast analog
servo loop to achieve maxi-
mum S/N ratio and frequency
stability.

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IF selectivity

The IF amplifier of the tuners is
where the adjacent and the
alternate channel selectivity is
created.

In TPT 3001 A the selectivity
can be swrtched to three diffe-
rent band-widths; WIDE, NOR-
MAL and NARROW, each one
optimum lor its particular com-
bination of station density and
conditions of reception.

ln WIDE and NORMAL the fil-

m Prov-mom: FM Tum not A

Mario

50er

ters are discrete LC types With
6 and 20 poles respectively.

In NARROW two symmetrical
high selectivity ceramic filters
are added to the 20 pole LC
filter of the NORMAL position,
resulting in an unsurpassed
combination of selectivity and
distortion free sound reproduc-
tion.

In TPT :30th the selectivity of
the IF circuits is determined by

a computer designed filter
whose characteristics are
slightly narrower than the
NORMAL position of TPT
3001Awith four, selected, high
quality ceramic filters of con-
stant group delay. This to take
advantage of a high selectivity
combined with a bandwith that
permits undistorted reception
also of strongly modulated
broadcasts

m 100 wid- Norm-iNurou

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ID. .300
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Harrow-din

The limiter

Both limiters have exceptional,
ly good AM suppression and
interference rejection, Moreov»
er they guarantee a constant

signal level output over a very
wide range of signal input
level.

The detector

Important for the overall quality
of a tuner is the performance
of the detector both with re-
spect to linearity, bandwidth
and signal to noise ratio.

In TPT 3001 A a fully discrete,

modified Foster Seeley" de-
tector is used having a band-
width of more than 4 MHz, to
avoid any distortion caused by
bandwidth limitations.

In TPT 301 1 A the detector is

part of the limiter with adjust»
able LC filters for perfect
matching to the IF amplifier.

The stereo
decoder

Equally important as all other
stages is the stereo decoder
forthe final result. The most
common deficiency of a stereo
decoder is the generation of
beat tones on heavy mod-
ulated signals. This property is
never specified for a tuner, but

very well audibly annoying for
a discerning listener.

To avoid this beat tone gen-
eration and to allow use of
Tandberg's unique Automatic
Noise Cancelling circuit, a dis-
crete stereo decoder is used in

the TPT 3001 A, more complex
in design than most complete
tuners

In TPT 3011A a specially
selected IC is used for optimal
performance

The audio circuit

To make a good tuner takes a
special knowledge of radio fre-
quency technology, but in
many cases the audio section
is neglected in terms of com-
ponent quality and design
criteria.

It is often in these audio stages

that the inferior sound quality

of FM is generated, and not as
is commonly believed that FM
is inherently an inferior source.

This is dealt with in TPT 3001A
and TPT 3011A by using the
same high standards of com-
ponent selections (polyester

and polypropylene caps, metal
film resistors) and design phi-
losophies (minimum negative
feedback applied in short
loops, etc).

As in the series 3000 audio
components.