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Search Mode - hand held
Connect the Rubber Duck Antenna
either directly to the F connector of the DisplayMax or using a three foot cable. (We
recommend using the cable to allow easier movement of the antenna). A dipole antenna can also be used for a hand held leakage
search. Be sure to hold the dipole horizontally. Rotate it on its axis to locate the leak source. The best reception will occur when the
dipole is parallel to the leak. Keep in mind, the leak source could be on either side of the dipole.
Tune to a video carrier in the 108 – 140 MHz range.
(Note: Channel 16 is the default setting in Leakage Setup)
Note: The DisplayMax uses a wide IF (280 KHz) for both signal level measurement and leakage detection. This eliminates
the need to adjust channel tuning for aeronautical offsets in either signal level or leakage modes. Accurate readings are
obtained by tuning to the standard frequencies of the video carriers.
Move the antenna through any area and along any cable where you suspect a leak.
Sources of leaks include:
Splices and fittings which may be loose, corroded or damaged.
Customer hook ups using low grade devices, no connectors, missing terminations.
TV Sets, VCRs, and computers.
Poorly made fittings.
Damaged, compressed or low quality cable.
Bad Converters.
Listen for any tone and watch the bar graph to determine if there is a leak.
The higher the pitch, the larger the leak. (Press FNC, Left/Right Arrow to adjust volume level)
At 3 ft, using the Rubber Duck antenna, the DisplayMax will pick up leaks equivalent to 4 uV/m at 10 ft.
No tone or bar graph indicates no leakage signal found.
Listen for a relatively slow warble tone.
It is important to differentiate leaks that are coming from your cable system from other signals that are in the air, such as motor noise,
aircraft communications, etc. The Displaymax incorporates a proprietary feature (patent pending) that produces a 4 Hz warble when
the received signal contains video (specifically, horizontal sync pulses). This feature allows the user to quickly identify the received
signal as a valid cable leak, or dismiss it as a non-cable signal. Keep in mind however, that a cable leak may be masked by a larger
non-cable signal. If a non-cable signal is narrow in bandwidth, such as a communications signal, it may be avoided by simply tuning
to a different channel. Cable leaks should remain fairly constant within the Displaymax’s leakage tuning range.
Locate the leak by moving the Rubber Duck around.
It will be most sensitive when held parallel to the leak and will null when pointed directly at the leak.
Listen for a faster warble on “tagged” channels.
Some cable systems employ a channel tagger that amplitude modulates one of the video carriers. This modulation, which is designed
to help differentiate the source of a leak, can be heard as fast warble on the audio tone of the leakage detector. In order to
differentiate this warble from the slower warble generated by all video carriers, we suggest you create a test leak of your tagged
channel and listen to the warble it creates. With a little experience, you will be easily able to distinguish the faster warble of most
tagging systems. Tagged channels are helpful in overbuild situations where a cable leak may be from one of two systems.
Reduce the leakage detector gain if necessary.
If the leak is very large, or you are very close to the source, (bar graph has peaked all the way to the top), you may need to reduce the
gain of the DisplayMax. Just press the F4 key to reduce the gain by 20 dB.
Change channels.
If you are still unsure of the source, change channels to see if the leak persists. Most cable leaks will be detectable on more than one
channel.
Switch on the Video Gating in Leakage Setup (Optional)
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