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VGA cable upgrade to Ultra High Performance cables
Video Graphics Array (VGA) is the analogue standard classification of display with a resolution of 640x480 which is being connected via a 15 pin high density Sub-D connector according to VGA industrial standard. Nowadays, VGA connectors are presented with much higher resolutions, causing it to be subject to much higher demands in order to be able to display these resolutions.
VGA cables are the most applied cable types within Digital Signage.
The basis of a VGA connection is an analogue control through separated colours. These three colours (red, green and blue, or in short RGB) are being transferred on a wire separately; the horizontal and vertical alignment are being controlled by a Hsync and Vsync (synchronisation). The analogue level of each of the colours red, green and blue determines the colour.
An image is being created by 480 lines of 640 pixels which are being positioned by the horizontal and vertical sync. A full screen is being composed 60 times per second (60Hz) to prevent blinking. The human eye detects a blink up to a refresh rate of 30 Hz. When exceeding 30 Hz, the human eye does not register a blink.
The higher the resolution, the more information will have tob e sent to the screen within a certain period of time (as shown in the illustration above).
Image composition on a monitor
Each VGA monitor has an internal clock with which every pixel is being refreshed (25,175 MHz). The refresh time for one pixel is 39,72 ns, rounded up to 40 ns. Each VGA monitor is being refreshed by means of vertical and horizontal synchronisation. In the left upper part of the screen, the refresh cycle is being started. After refreshing the first pixel, the pixels next in line will be refreshed.
As soon as the monitor receives a horizontal refresh impulse, the following row refresh cycle will start. This process is being repeated up to the last row of the screen. As soon as the last pixel of the last row is being refreshed, a new vertical synchronisation impulse creates a new screen. Times mentioned are applicable to a 640x480 VGA resolution.
The link between resolution and bandwidth
Information transfer is being defined in bandwidth.
For example:
1600 x 1200 x 85 Hz x 1,2/1.000.000 = 195,8 MHz (approx. 200 MHz)
This enables people to determine that the resolution level and refresh rate influence bandwidth. In other words: in case of higher resolutions and refresh rates, image signals must be transferred with higher frequencies.
How to prevent poor image quality
As light and sound,current also has a wave velocity. For example, there is a difference in the moment of flash and thunder detection in case of thunder and lightning. This phenomonon also applies to the moments in which a signal is sent and received. A high quality VGA cable provides a specific time frame in which these observations can be realised, zo the receiver in the monitor is able to merge both signals into one good signal.
When the transit time of the RGB coax wires of a cable differ, the horizontal sync (the signal that defines when the RGB signals are being captured) will capture the RGB signals on a wrong moment and write these in on the screen, causing a distortion.
Ultra High Performance cables
In order to prevent these distortions, Intronics upgraded its VGA cables to a higher level. The cables consist of 3x UL20276 coaxial wires (RGB) which are being shielded with spiral foil (additionally, cables >10 metres are equipped with a 65% wired shielding) and 6x UL1589 steering wires; all of these materials (coax and steering wires) are fully shielded with aluminium/mylar foil and a 85% wired shielding.
The Ultra High Performance cables are made of flexible, smooth ACT cable. The AK49xx range is fitted with patented cast started ACT hoods. The AK93xx range is fitted with patented full metal ACT hoods which make the use of ferrite cores redundant.
All Ultra High Performance cables are supplied with a test report.
