— 19 —
employed on a sporadic basis. Groups the station transmits
will appear on the list, but some may indicate 0.00% activity
at the moment.
PTY Type
(Menu Screen 16)
The PTY (Program TYpe) function of the RDS system lets a
listener put the search for preferred programming entirely
into the hands of his radio. Two PTY lists define ‘Station
Format’ (N. America) or ‘Program Type’ (Europe). The re-
gional/cultural basis for separate lists remains the primary
difference between the North American RBDS and the Euro-
pean RDS Standards. An RDS radio will display items from
a different list of programming choices depending on what
market it has been manufactured for.
The 633 receiver is able to decode PTY from either list and
display the proper description of programming in Menu
Screen 7. Push the knob on this screen and
PTY TYPE
will
begin to blink. Turn the
knob to specify either
the
North America
or
the
Europe
list, and then
push the knob again to
transfer the choice to
memory.
Program Audio De-Emphasis
(Menu Screen 17)
De-emphasis for the program audio is selected here. 75µs
(75-microsecond) de-emphasis is standard for the Western
Hemisphere, and 50µs
for Europe and most of
the rest of the world.
Push and turn the knob
to select, push again to
set in memory.
Audio High-Cut Filter
(Menu Screen 18)
The 633 receiver incorporates a user-selectable and gentle
low-pass filter that may
be inserted into both the
L/R analog and AES digi-
tal line outputs. This
filter allows the user to
roll off the higher audio
— 20 —
frequencies at his discretion to reduce the audibility of hiss-
type noise under poor reception conditions.
The default setting for this filter is
Disabled
. As may be
required, however, it can be set for an HF cutoff of
15kHz
,
10kHz
,
8kHz
,
6kHz
,
5kHz
and
4kHz
.
The cutoff frequency shown in this menu is approximately
the -3dB point of the filter. The filter slope is not a straight-
line function, becoming steeper as the frequency increases.
Before implementing this fixed HF rolloff to reduce noise,
you might first try the automatic stereo-to-mono ‘blending’
option afforded in Menu Screen 4:
StMode:Blend-St
. This
is a program-controlled function that reduces stereo separa-
tion (hence, noise) only under poor reception conditions.
IF Bandwidth Control
(Menu Screen 19)
This menu is a bit of a misnomer, as this DSP-based receiver
really doesn’t have an intermediate frequency (IF) as such.
But the utility of this menu equates to the same function in
a traditional analog receiver.
The maximum reception
bandwidth of the 633 re-
ceiver is ±110kHz. The
default setting, however
is
Auto
(automatic). In
this mode receive band-
width is subject to restriction based on signal reception
conditions. The receiver pulls in the band edges as either
the high-frequency noise component of the baseband signal
increases or as the signal from an adjacent channel en-
croaches.
Fixed bandwidth values may be manually selected as well.
Push and turn the knob to select:
110kHz
,
84kHz
,
60kHz
or
40kHz
. Unlike AM radio, you won’t hear the high frequen-
cies roll off as receive bandwidth is reduced. Instead, stereo
separation and harmonic distortion performance will be
compromised to a greater or lesser extent. If the Auto set-
ting is not effective in lessening ‘splatter’ from an adjacent
channel, try the lower cutoff frequencies to reduce interfer-
ence. When a setting is selected, push the knob again to set
in memory.
