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23 February 2025

ALLEN AVIONICS VIT-75-3 ANALOGUE VIDEO ISOLATION TRANSFORMER 3 channel

Stock code
90-6317
Brand
Allen Avionics
Model number
  • VIT-75-3
ALLEN AVIONICS VIT-75-3 ANALOGUE VIDEO ISOLATION TRANSFORMER 3 channel
ALLEN AVIONICS VIT-75-3 ANALOGUE VIDEO ISOLATION TRANSFORMER 3 channel

ALLEN AVIONICS ANALOGUE VIDEO GROUND LOOP HUM ELIMINATORS AND ISOLATORS

A hum eliminator or isolation transformer can be inserted at points within an installation at which it is observed that performance degrades. Applications include sports stadiums and large arenas where it is very difficult to know where different earth potentials exist. Identification of the problem areas is undertaken by simplifying the circuits as much as possible, until satisfactory performance is obtained, and then re-introducing additional elements until the offending equipment is found which will indicate where a loop eliminator should be inserted.

Hum is the term for low-frequency noise induced by alternating currents at 50Hz or 60Hz in AC mains power lines. There are two main sources of hum and two types of hum-elimination available from Allen Avionics. Hum can appear on video signals because it has been induced in a ground-loop, or introduced because of a real voltage potential difference (p.d.) between the grounds on the transmitting and receiving equipment. In many installations, equipment racks are powered, unavoidably, from different supplies. This can easily lead to induced hum on video signals. These effects are often seen where signals are fed from floor to floor within buildings and can be very significant when they are passed from building to building. Probably the worst environment is the outside broadcast where multiple generators or AC power cables may be in close proximity to the equipment racks or video cables, inducing tens of volts of ripple on the coaxial cable screens.

Video Hum Eliminators - Analogue

Video Isolation Transformers

Isolation transformers are most suited to applications where there are large earth potential differences, greater than 20 volts, between sections of an installation.

They are especially useful in outside broadcast or temporary installations, or between buildings where different power supplies and earth points are present. Breaking the ground connection in the video transmission line will eliminate the 50Hz or 60Hz hum currents in the ground loops. The VIT- 75 video isolation transformers provide true electrical isolation, with no DC path and 500V DC breakdown voltage between input and output, while passing the video signals completely unaltered. (Note: provision should be made for circuits such as camera power or control, requiring transmission of DC through the video coax line.)

Allen Avionics video isolation transformers are housed in extremely rugged, waterproof, high impact ABS or die-cast metal cases. BNC input and output connectors are located on the top, or front face and the VIT-75-3 has stainless steel hoop guards either side of the connectors for protection during transit and rigging. Four threaded mounting holes are provided on the rear face of the units.


VIT-75 - Video Isolation Transformer, 1 channel

Video signal format: Composite. Impedance: 75 ohms. Bandwidth: 20Hz to 6MHz. Video isolation: 100M ohms minimum. Insertion loss: 1.0dB maximum. Return Loss: 20dB minimum. Case: High impact ABS. Mounting holes: 8-32 x 1.5 inches. Dimensions: 95 x 67 x 38mm. Weight: 0.45kg.


VIT-75-3 - Video Isolation Transformer, 3 channel

Three independent video isolation transformer channels in a single unit. Specification as VIT-75 except:
Isolation between channels: 60dB typical. Case: Die cast metal. Mounting holes: 6-32 x 1.5 inches. Dimensions: 120 x 94 x 27mm. Weight: 1.14kg.

Many other hum blockers, isolators, transformers, video noise eliminators, attenuators and delay lines are available from Allen Avionics, to assist with the removal of unwanted interference, synchronisation and equalisation in video and audio systems. Formats include SDI-HD, Component and composite video, CATV, S-VHS and analogue audio. Packaging options include stand-alone modules, card and rack frame enclosures and discrete PCB mounting components.


SDI-VIT-75 - SD Video Isolation Transformer

Video signal format: SD-SDI to SMPTE259M and ITU-R BT 656 between 143Mb/s and 540 Mb/s. Impedance: 75 ohms. Bandwidth: 1.0GHz. Ground loop isolation: Better than 60dB. Return loss: Better than 15dB to 500MHz. Insertion loss: Equivalent to approximately 6m of Canford SDV-L, Draka 1.0/4.8AF or Belden 1694A. Dimensions: 57 x 17.5 Dia mm.


HD-VIT-75 - HD Video Isolation Transformer

Video signal format: HD-SDI to SMPTE292M up to 1.5Gb/s. Impedance: 75 ohms. Bandwidth: 3.0GHz. Ground loop isolation: Better than 60dB. Return loss: Better than 15dB to 1.5GHz. Insertion loss: Equivalent to approximately 6m of Canford SDV-L, Draka 1.0/4.8AF or Belden 1694A. Dimensions: 54 x 21.6 diameter, mm.

Many other hum blockers, isolators, transformers, video noise eliminators, attenuators and delay lines are available from Allen Avionics to assist with the removal of unwanted interference, synchronisation and equalisation in video and audio systems. Formats include SDI-HD, component and composite video, CATV, S-VHS and analogue audio. Packaging options include stand-alone modules, card and rack frame enclosures and discrete PCB mounting components.