Standard AHD is an open video signal transmission system without delay supporting the following resolutions:
AHD-L – 960 x 576 px (PAL)
AHD-M – 1280 x 720 px
AHD-H – 1920 x 1080 px
3 Mpx – 2048 x 1536 px
4 Mpx – 2560 x 1440 px
5 Mpx – 2592 x 1944 px
Fig. 1. Screenshot from AHD camera at 1080p
Fig. 2. Screenshot from AHD camera at 720p
AHD camera signal can be transmitted via low quality coaxial cable as an alternative for analogue display device users. There is no need to replace cables when switching to HD resolution. The maximum distance may vary depending on the coaxial cable quality. For example, for RG-59 cables, the maximum distance is approx. 400 m at 1080p. At 720p, the maximum distance is approx. 500 m. At higher distances, the image quality will gradually deteriorate. The maximum distance can be extended with higher quality cables.
The camera signal can also be transmitted using the twisted pair with video baluns. The maximum distance depends on the video balun used. The limit distance is 150 m, and above that, the quality in most cases will deteriorate significantly.
Fig. 3. Screenshot from the camera connected via UTP 150 m (TR-1M balun)
AHD recorders are compatible with AHD and PAL cameras. Depending on the recorder, the cameras can be replaced in pairs or in any configuration. The AHD system can be introduced gradually and does not require all the cameras to be replaced at once.
Most AHD cameras allow switching between AHD/PAL output standards. The standard is usually switched with a joystick on the camera cable (move the joystick right or left and hold for approx. 5 s) - Fig. 4.
Fig. 5. Screenshot from AHD camera in PAL mode
The biggest advantage of the AHD system monitoring is its price to quality ratio. Full HD monitoring is now available at relatively low costs. Another major advantage is no delay in data transmission and easy configuration.
Detailed parameters of the standard can be found in the article: