NTSC TV with an HD Set-top Box
In some cases, it may be desirable to add DTV/HDTV reception
to a existing NTSC television ahead of its later replacement by an HD television or
monitor (i.e. if you have purchased an HD STB but have not yet purchased an HDTV). If the
television is a recent model, with large screen, good audio and flexible external
connectivity, it may be satisfactory as an interim solution. SDTV and HDTV programs will
be displayed on it at less than their full quality, but never-the-less at a significantly
better quality than that of current NTSC programs, free from interference and ghosting.
Some care in programming the STB is required to ensure that the HD pictures in 16:9 aspect
ratio are displayed in letterbox format on the 4:3 aspect ratio of the legacy television.
The STB will decode the Dolby Digital audio of the HDTV program into stereo audio for the
legacy television, or for an external stereo sound system.
The capabilities of existing NTSC televisions to handle external signals are highly
variable, but as a minimum, connection to a legacy television requires an external A/V
port including an NTSC or S-Video (better) input and an analog L/R audio input. Connection
through an RF channel 3/4 input will compromise the picture quality excessively. The
connection of a VCR and/or DVD may pose a problem if only a single A/V port exists and in
this case, an additional selector or distribution amplifier may be required to obtain the
desired result. The figures below offer some suggestions here.
In essence, the set-up includes:
Existing NTSC television, preferably with large screen, good audio and external A/V
Terrestrial 8VSB, Satellite or Cable STB;
VCR, if desired.
DVD, if desired
Antenna, set-top, internal or roof-top, appropriately selected for reception at your
- Connect the HDTV
source (off-air, satellite or cable) to the Antenna or Cable inputs to the STB using the
coaxial cable with screw-on F connectors.
- Connect video and
audio using the RCA cables. (Better performance is obtained if a high quality cable is
used for the video, or if an S-Video connection can be utilized);
- Set up the STB for
480i composite output, corresponding to the format of the TV.
- A DVD player may be
connected either to second input of the TV , (sometimes on the front) or to an input on
the STB, dependent on design. If neither are possible, a multi-input
selector switch (e.g. Tandy 15-8252 or 15-1977) may be connected to the input to
the TV .
- The baseband
video/audio input (RCA connectors) of a VCR may be connected to the output of the TV set
(if available, using RCA cables) for recording the current program. If an additional
connection to the STB is required, a distribution amplifier
may be used (Tandy 15-8272). The Baseband video/audio output of the VCR may be connected
to an input on the TV or to the accessory switch using RCA cables.