R
ron_the_rascal
Guest
This post is for anyone having a problem with mosaic dropout or the dreaded red spot.
The OnD(and all terrestrial digital) signals are broadcast in a series of six multiplexes or muxes, each mux occupying the space of one old analogue channel. Each mux is 8Mhz wide and can transmit up to 10 digital channels(with MPEG2 compression)with a maximum data rate of 20Mbits/second.In reality this number of digital channels is reduced because the quality of the output is still a direct function of the bandwidth, (more of this another time).
The muxes are allocated a channel number in the same way as the analogue channels, however to avoid interference with other transmitters the power is greatly reduced and the channels may be spaced out widely over the UHF band.
All TV antennas are grouped according to frequency, that is to say their response is optimized for the band of frequencies being received. If the digital muxes lie outside the band of the analogue channels then the antenna gain for the mux frequencies will be reduced and also the received signal strength.
You first need to know which transmitter you are looking at and then which group of frequencies the muxes are on. A good link for this is.
web page
Briefly, if the muxes are located in a specific group then a high gain Yagi antenna is the best option and if they are spread out widely over the UHF band then a log periodic antenna gives the best wideband response.
If you are lucky then the analogue channels and digital muxes are in the same group. A good example of this is the Crystal Palace transmitter. This was done for a reason as this transmitter serves a huge catchment and it means that if you are receiving good analogue pictures you will not need to change your antenna for the digital muxes. Sadly we are not all so lucky.
If there is any interest in this post I'll be happy to cover more on the subject
Party ON!
The OnD(and all terrestrial digital) signals are broadcast in a series of six multiplexes or muxes, each mux occupying the space of one old analogue channel. Each mux is 8Mhz wide and can transmit up to 10 digital channels(with MPEG2 compression)with a maximum data rate of 20Mbits/second.In reality this number of digital channels is reduced because the quality of the output is still a direct function of the bandwidth, (more of this another time).
The muxes are allocated a channel number in the same way as the analogue channels, however to avoid interference with other transmitters the power is greatly reduced and the channels may be spaced out widely over the UHF band.
All TV antennas are grouped according to frequency, that is to say their response is optimized for the band of frequencies being received. If the digital muxes lie outside the band of the analogue channels then the antenna gain for the mux frequencies will be reduced and also the received signal strength.
You first need to know which transmitter you are looking at and then which group of frequencies the muxes are on. A good link for this is.
web page
Briefly, if the muxes are located in a specific group then a high gain Yagi antenna is the best option and if they are spread out widely over the UHF band then a log periodic antenna gives the best wideband response.
If you are lucky then the analogue channels and digital muxes are in the same group. A good example of this is the Crystal Palace transmitter. This was done for a reason as this transmitter serves a huge catchment and it means that if you are receiving good analogue pictures you will not need to change your antenna for the digital muxes. Sadly we are not all so lucky.
If there is any interest in this post I'll be happy to cover more on the subject
Party ON!
