Typical Connections
In normal usage, the desired RF Channel is chosen on the RF Channel Select
switch as previously described. The power adapter is connected to the converter and
to the AC power source. A valid NTSC or PAL/SECAM video source should then
be connected to the video input. The video source can be anything from a VCR to a
DVD to an off-air broadcast. For the best quality, a DVD or PVR is recommended.
The video output can then be connected to the input of a video monitor, or the RF
output can be connected to the antenna terminals of a television. A balance
transformer may be needed to convert the 75 ohm output of the unit to the
appropriate signal type for the television.
Caution!
The RF output from the internal modulator uses a double side band
modulation technique, and is not suitable for broadcast without filtering. Also, due to
the method of frequency division provided in the RF modulator IC’s, their outputs
are rich in harmonics. It is intended to only be connected directly to a television’s
antenna input. At no time should the RF output from this unit be connected to an
antenna for the purpose of broadcasting the signal. While no damage will result to the
unit, it is against the law in most countries to use a modulator in such a manor.
The audio from the source device (VCR, DVD, etc.) should be routed to the
converters audio inputs. Two inputs are provided with low cross talk so a stereo audio
signal can be fed to the unit. The two channels are combined into a mono signal. If
only a mono audio source is available, it can be fed to either input. For additional
audio gain, a “Y” cable can be used with a mono source to feed both inputs.
The use of high quality video cables is recommended for best results. Cables
conforming to 75 ohm impedance should be used on the video inputs and outputs.
Cables of lesser quality can be used for the audio channels.
There should now be a solid status light on the front panel indicating a locked
video signal as described previously, and a stable image on the television.
To help aid in setup, when no video input is presented to the converter, it will
output a default image. This can be useful in making final adjustments to the
television.
The audio level control can be adjusted to set the audio RF modulation depth for
the connected source. This control should be set to the maximum setting without
causing distortion of the audio. If the audio is distorted, this control should be lowered
slightly. If the audio is low in volume or noisy, this control should be raised. It can be
adjusted my inserting a small flat blade screw driver in the hole in the front panel. A
clockwise turn will increase the level, while the opposite will decrease the level.
An additional benefit of the converter can be found in it’s video processing path.
Since most early television sets did not have Vertical Blanking Interval Suppression,
or Chroma Traps, retrace lines and moire patterns can be visible when using modern
video signals. The converter will suppress the VBI signals eliminating retrace lines,
and contains a 4 line adaptive comb filter to remove the chroma signal eliminating
moire patterns.
Introduction
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